Immunological Testing

Immunological Testing

Natural Killer cells

Natural Killer Cells

Understanding Natural Killer Cells in Reproduction: Their Role in Pregnancy Loss, Infertility, and Implantation Failure

What Are Natural Killer Cells?

Natural killer cells — often called “NK cells” — are a type of white blood cell that is part of your body’s immune system. Despite their fierce-sounding name, NK cells are not always about killing. In fact, when it comes to pregnancy, a special group of NK cells in your uterus plays a vital role in helping — not harming — your baby.

To understand how NK cells affect fertility and pregnancy, it is important to know that there are two very different populations of NK cells that matter in reproduction:

1. Peripheral blood NK cells (pNK cells) — the NK cells circulating in your bloodstream.

2. Uterine NK cells (uNK cells) — a specialized population that lives in the lining of your uterus.

These two types of NK cells look different, behave differently, and have very different jobs. Understanding this distinction is one of the most important concepts in reproductive immunology.

Two Types of NK Cells: A Simple Way to Think About It

Imagine your immune system as a security team for a building.

Peripheral blood NK cells (pNK cells) are like the security guards who patrol the streets outside. Their main job is to find and destroy threats — viruses, infections, and abnormal cells like cancer. They are trained fighters. In healthy people, pNK cells make up about 10–15% of the white blood cells in the bloodstream.

Uterine NK cells (uNK cells) are like the interior design team inside the building. They are not there to fight. Instead, they are specialized helpers whose job is to prepare the uterus for pregnancy. They help remodel the blood vessels in the uterine lining so that the placenta can receive a rich blood supply. They guide the embryo as it burrows into the uterine wall during implantation. And they help create an environment of immune tolerance — teaching the mother’s immune system to accept the embryo rather than reject it.

During the first trimester of pregnancy, uNK cells make up an astonishing 50–70% of all immune cells in the uterine lining. They are the dominant immune population at the site where the embryo implants.

Here is a key point: pNK cells and uNK cells are not the same. They have different markers on their surface, different internal machinery, and different functions. The pNK cells in your blood are predominantly “CD56-dim” cells — efficient killers. The uNK cells in your uterus are predominantly “CD56-bright” cells — nurturers and builders. Even though uNK cells contain the same killing molecules (perforin and granzymes) as blood NK cells, they are held in check and rarely use them. Instead, they release growth factors, cytokines, and signals that support the pregnancy.

How NK Cells Help a Healthy Pregnancy

For a pregnancy to succeed, several things must happen in the right order:

– Implantation: The embryo must attach to and burrow into the uterine lining.

– Spiral artery remodeling: The small blood vessels in the uterine wall must widen and transform so they can deliver enough blood to the growing placenta.

– Immune tolerance: The mother’s immune system must recognize the embryo — which carries genetic material from the father — and choose to protect it rather than attack it.

Uterine NK cells are involved in all three of these critical steps. They communicate with the embryo’s outer cells (called trophoblast cells) through a sophisticated system of receptors and signals. One of the most important interactions involves receptors on the NK cells called KIR (killer immunoglobulin-like receptors) and molecules on the embryo’s cells called HLA-C (human leukocyte antigen C).

 

When NK Cells Go Wrong: The Connection to Pregnancy Loss, Infertility, and Implantation Failure

Natural Killer (NK) cells play a vital role in reproductive health, and their proper functioning is crucial for successful pregnancy outcomes. When the NK cell system is disrupted, it can contribute to several reproductive challenges, including recurrent miscarriage, unexplained infertility, and repeated failed embryo transfers during IVF. Research has identified a number of NK cell abnormalities shared by women experiencing these issues.

Higher Numbers of NK Cells in the Blood: Multiple studies have observed that women with recurrent miscarriage and unexplained infertility often have a higher percentage of peripheral NK (pNK) cells in their bloodstream. In addition, some of these women exhibit signs of heightened immune activation, suggesting a broader immune imbalance that may negatively impact the uterine environment.

Increased NK Cell Activity (Cytotoxicity): The activity level of NK cells, not just their quantity, is significant. NK cell cytotoxicity refers to how readily these cells destroy target cells in laboratory tests. Women with recurrent miscarriage have been shown to possess significantly higher NK cell cytotoxicity, and elevated cytotoxicity is associated with an increased risk of subsequent pregnancy loss.

Elevated Uterine NK Cell Density: A systematic review and meta-analysis found that women with both recurrent miscarriage and recurrent implantation failure have significantly higher levels of uterine NK (uNK) cells in the uterine lining compared to women with uncomplicated fertility.

Altered NK Cell Receptors: Abnormal expression of certain receptors on NK cells has been identified in women with recurrent implantation failure and recurrent miscarriage. Specifically, these women tend to have lower levels of inhibitory receptors (such as ILT2 and NKG2D) and higher levels of activating receptors (like NKp46). This imbalance can disrupt the crucial communication between the mother’s immune cells and the embryo, leading to rejection rather than tolerance.

KIR/HLA-C Mismatch: Certain genetic combinations between the mother’s KIR receptors and the embryo’s HLA-C molecules have been linked to implantation failure and pregnancy loss. In particular, women with the “KIR AA” genotype, which lacks activating KIR receptors, seem to be at higher risk—especially when the embryo carries specific HLA-C types. This finding indicates that insufficient NK cell activation, not just excessive activation, can hinder proper support for trophoblast invasion and blood vessel remodeling.

 

Testing: What Can Be Measured?

There are several types of NK cell tests that may be part of a reproductive immunology evaluation:

Blood-based tests (peripheral NK cells):

– NK cell percentage: Measures what proportion of your white blood cells are NK cells. In healthy individuals, NK cells typically make up about 10–15% of lymphocytes. Some reproductive immunologists consider levels above 12% or above 15% (depending on the laboratory) to be elevated.

– NK cell cytotoxicity (NKc): Measures how effectively your NK cells kill target cells in a laboratory setting. This is a functional test — it tells you not just how many NK cells you have, but how aggressively they behave.

Uterine-based tests:

– Endometrial biopsy with immune cell analysis: A small sample of the uterine lining is taken (usually during the luteal phase of the menstrual cycle) and analyzed using flow cytometry to count and characterize the uNK cells directly. This provides a more direct picture of the immune environment where implantation occurs.

An important note: There is ongoing scientific debate about the clinical value of peripheral blood NK cell testing. A key finding from research is that pNK cell levels in the blood do not reliably correlate with uNK cell levels in the uterus. This means that a blood test alone may not accurately reflect what is happening inside the uterus. For this reason, many reproductive immunology specialists recommend evaluating both blood and uterine NK cells when possible, and interpreting results in the context of the full clinical picture.

What This Means for You

If you have experienced recurrent pregnancy loss, unexplained infertility, or multiple failed embryo transfers during IVF, an evaluation of your NK cell profile — both in the blood and, when appropriate, in the uterine lining — may reveal important information that standard fertility testing misses.

It is important to understand that:

– NK cells are not your enemy. They are essential for a healthy pregnancy. The goal of treatment is to restore balance, not to suppress your immune system entirely.

– Not every woman with reproductive difficulties has an NK cell problem. A thorough evaluation is needed to determine whether immune factors are contributing to your specific situation.

– The field of reproductive immunology is advancing rapidly. What was once dismissed as “unexplained” is increasingly becoming explainable — and treatable.

– Treatment should always be guided by proper testing and an experienced specialist who can interpret the results in the context of your complete medical history.

The science is clear: your immune system plays a central and active role in every pregnancy, from the very first moment of implantation. By understanding and addressing NK cell dysfunction, many couples who have struggled with repeated losses or failed treatments are finding new paths to successful pregnancies.

 

References:

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T-Helper 1 / T-Helper 2 Cytokines ratio

T-Helper 1 / T-Helper 2 Cytokines ratio

Understanding the Th1/Th2 Cytokine Balance: Why It Matters for Pregnancy

Your Immune System Has Two Modes — and Pregnancy Requires the Right One

Your immune system is not a single, uniform defense force. It has different “modes” of operation, and one of the most important distinctions in reproductive medicine involves two types of immune responses called Th1 and Th2.

Th1 and Th2 refer to two subsets of a type of white blood cell called a T helper cell (the “Th” stands for “T helper”). These cells act as commanders of the immune system, directing how the body responds to threats. Each subset produces its own set of chemical messengers called cytokines, and these cytokines have very different effects on the body — and on pregnancy.

Th1 Cells: The Fighters

Th1 cells are the pro-inflammatory arm of the immune system. They produce cytokines designed to fight infections and destroy foreign invaders. The key Th1 cytokines include:

  • TNF-alpha (Tumor Necrosis Factor-alpha): A powerful inflammatory molecule that activates immune cells and promotes inflammation.

  • IFN-gamma (Interferon-gamma): A cytokine that enhances the killing ability of immune cells.

  • IL-2 (Interleukin-2): A growth factor that stimulates the expansion of immune cells.

In everyday life, Th1 responses are essential — they help fight viruses, bacteria, and abnormal cells. But during pregnancy, an overactive Th1 response can be harmful.

Th2 Cells: The Protectors

Th2 cells are the anti-inflammatory arm of the immune system. They produce cytokines that calm the immune response and promote tolerance. The key Th2 cytokines include:

  • IL-4 (Interleukin-4): Suppresses Th1 activity and promotes a calming immune environment.

  • IL-10 (Interleukin-10): A powerful anti-inflammatory cytokine that helps prevent excessive immune reactions.

  • IL-6 (Interleukin-6): Supports humoral (antibody-based) immunity.

During pregnancy, Th2 responses help create an environment of immune tolerance — teaching the mother’s body to accept and protect the developing embryo rather than attack it.

The Th1/Th2 Balance in Normal Pregnancy

For a pregnancy to succeed, the mother’s immune system must perform a remarkable shift. The embryo carries genetic material from both parents, which means it is partially “foreign” to the mother’s immune system. If the immune system treated the embryo the way it treats a virus or a transplanted organ, it would attack and reject it.

In a healthy pregnancy, the body naturally shifts from a Th1-dominant state to a Th2-dominant state shortly after the embryo implants. This shift is orchestrated by hormones — particularly progesterone — and by signals from the embryo and placenta themselves.

Here is how the immune environment changes across pregnancy:

  • During implantation: A brief, controlled Th1 inflammatory response is actually needed. This inflammation helps the embryo burrow into the uterine lining and triggers the remodeling of blood vessels that will supply the placenta.

  • After implantation: The immune environment must quickly shift to Th2 dominance. This anti-inflammatory state protects the embryo from immune attack and supports placental development and fetal growth.

  • At delivery: The immune system shifts back toward Th1 to help initiate labor and delivery.

This carefully timed sequence — inflammation, then tolerance, then inflammation again — is essential for a healthy pregnancy from start to finish.

When the Balance Goes Wrong: Th1 Dominance and Reproductive Failure

Problems arise when the immune system fails to make the shift from Th1 to Th2 after implantation. If the Th1 response remains too strong — a condition called Th1 dominance — the resulting inflammatory environment can be hostile to the embryo.

Research has shown that women with recurrent pregnancy loss, unexplained infertility, and repeated implantation failure during IVF often have significantly elevated Th1/Th2 ratios in their blood compared to women with successful pregnancies. Specifically:

  • Women with recurrent miscarriage have been found to have higher ratios of TNF-alpha/IL-10, and IFN-gamma/IL-10 in their T helper cells.

  • Women with multiple IVF failures — even without a history of miscarriage — also show elevated TNF-alpha/IL-10 and TNF-alpha/IL-10 ratios.

How Does Th1 Dominance Harm Pregnancy?

When Th1 cytokines are elevated, they can damage a pregnancy through several mechanisms:

  • TNF-alpha can activate macrophages (immune cells) that attack the trophoblast — the outer layer of the embryo that forms the placenta. It can also activate blood clotting pathways in the blood vessels that supply the placenta, cutting off blood flow.

  • IFN-gamma can directly impair trophoblast growth and invasion, preventing the embryo from properly establishing itself in the uterine wall.

  • Together, these pro-inflammatory cytokines create an environment that promotes embryo rejection rather than acceptance.

At the same time, when Th2 cytokines like IL-4 and IL-10 are insufficient, the body lacks the protective, anti-inflammatory signals needed to shield the embryo from immune attack.

Beyond Th1/Th2: The Expanded Picture — Th17 and Regulatory T Cells

While the Th1/Th2 balance was the original framework for understanding immune-related pregnancy failure, scientists have since discovered additional immune players that are equally important:

  • Th17 cells are another pro-inflammatory subset that produces IL-17. Women with recurrent miscarriage have been found to have significantly elevated Th17 cells. Excessive Th17 activity can drive inflammation at the maternal-fetal interface.

  • Regulatory T cells (Tregs) are the immune system’s peacekeepers. They suppress excessive immune reactions and promote tolerance. Women with recurrent pregnancy loss often have fewer Tregs, and the ratio of Th17 to Treg cells is elevated — meaning the balance tips toward inflammation and away from tolerance.

The modern understanding of reproductive immunology now considers the Th1/Th2 balance alongside the Th17/Treg balance. Together, these four cell types form a complex network that determines whether the immune environment is welcoming or hostile to a pregnancy.

How Is the Th1/Th2 Ratio Tested?

The Th1/Th2 cytokine ratio is measured through a blood test. A sample of peripheral blood is drawn, and the immune cells are analyzed using a technique called flow cytometry. This technology can measure the cytokines produced inside individual T helper cells, allowing the laboratory to determine:

  • The percentage of T cells producing Th1 cytokines (TNF-alpha, IFN-gamma)

  • The percentage of T cells producing Th2 cytokines (IL-10)

  • The ratios between them (such as TNF-alpha/IL-10 or IFN-gamma/IL-10)

The most commonly evaluated ratios include:

  • TNF-alpha/IL-10 ratio

  • IFN-gamma/IL-10 ratio

When these ratios are elevated above established reference ranges, it suggests that the immune system is in a pro-inflammatory, Th1-dominant state that may be contributing to reproductive failure.

An important note: The Th1/Th2 ratio should always be interpreted in the context of the full clinical picture — including NK cell testing, autoimmune markers, and your complete medical history. A single test result does not tell the whole story. A reproductive immunology specialist can help determine whether your specific immune profile is contributing to your reproductive challenges.

What This Means for You

If you have experienced recurrent pregnancy loss, unexplained infertility, or multiple failed embryo transfers during IVF, an evaluation of your Th1/Th2 cytokine balance may reveal an important piece of the puzzle that standard fertility testing misses.

Key points to remember:

  • The Th1/Th2 balance is a critical factor in whether your immune system supports or undermines pregnancy.

  • An elevated Th1/Th2 ratio creates a pro-inflammatory environment that can prevent implantation, damage the placenta, and lead to pregnancy loss.

  • This imbalance is measurable through a blood test and is treatable with targeted immunomodulatory therapies.

  • Treatment is not about weakening your immune system — it is about restoring the natural balance that every healthy pregnancy requires.

  • The field of reproductive immunology is advancing rapidly, and what was once labeled “unexplained” is increasingly becoming explainable — and treatable.

  • Treatment should always be guided by proper testing and an experienced reproductive immunology specialist who can interpret the results in the context of your complete medical history.

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Antiphospholipid Antibodies

Antiphospholipid Antibodies

Understanding Antiphospholipid Antibodies in Reproductive Failure: Criteria, Non-Criteria, and the Immune System’s Role

What Are Antiphospholipid Antibodies?

Antiphospholipid antibodies — often shortened to “aPL” — are a group of autoantibodies produced by your immune system. In a healthy body, antibodies are designed to fight infections. But in some people, the immune system makes a mistake: it produces antibodies that target the body’s own tissues, specifically proteins attached to phospholipids — the building blocks of every cell membrane in your body.

These antibodies are not rare. They are found in approximately 15% of women with recurrent pregnancy loss, and Antiphospholipid Syndrome (APS) is considered the most important treatable cause of recurrent miscarriage.

“Criteria” Antiphospholipid Antibodies: The Standard Tests

The international medical community has established classification criteria for diagnosing APS. The antibodies included in these official criteria are called “criteria” antiphospholipid antibodies. There are three:

  • Lupus Anticoagulant (LA): Despite its confusing name, this is not a test for lupus, and it does not cause anticoagulation (blood thinning). It is actually a functional test that measures how antiphospholipid antibodies interfere with clotting reactions in a test tube. Paradoxically, in the body, it promotes clotting. Among all antiphospholipid antibodies, lupus anticoagulant carries the greatest risk for adverse pregnancy outcomes.
  • Anticardiolipin Antibodies (aCL): These antibodies target cardiolipin, a phospholipid found in cell membranes. They are measured as IgG, IgM, and IgA isotypes.
  • Anti-β2-Glycoprotein I Antibodies (anti-β2GPI): β2-glycoprotein I is a protein that binds to phospholipids on cell surfaces. These antibodies target this protein and are measured as IgG, IgM, and IgA isotypes.

For a diagnosis of APS, at least one of these antibodies must be positive on two separate occasions, at least 12 weeks apart. This requirement for “persistent” positivity is important because temporary elevations can occur with infections or medications and do not carry the same clinical significance.

The risk profile matters: patients who are “triple positive” — meaning all three criteria antibodies are positive — are at the highest risk for both thrombosis and pregnancy complications.

The 2023 ACR/EULAR Classification Update

In 2023, the American College of Rheumatology (ACR) and the European Alliance of Associations for Rheumatology (EULAR) published updated classification criteria for APS. These new criteria use a weighted scoring system across clinical domains (including an obstetric domain) and laboratory domains. Patients must accumulate at least 3 points from clinical criteria and at least 3 points from laboratory criteria to be classified as having APS.

An important point: These updated criteria were designed for research classification with very high specificity (99%), but they are stricter than the previous criteria. This means that some patients — particularly those with obstetric APS — may not meet the new research classification even though they have clinically significant disease. A significant proportion of patients with obstetric APS do not fulfill these research criteria. The new criteria are not intended to replace clinical judgment in diagnosing and treating individual patients.

“Non-Criteria” Antiphospholipid Antibodies: The Hidden Players

Here is where reproductive immunology goes deeper. The three criteria antibodies are not the only antiphospholipid antibodies that exist. There is a growing family of “non-criteria” antibodies — antibodies that are associated with pregnancy complications but are not yet included in the official classification criteria.

These antibodies are particularly important because many women with clinical features of APS test negative for all three criteria antibodies. This condition is called “seronegative APS.” Studies have shown that non-criteria antibodies can identify up to 60.9% of these seronegative patients who would otherwise remain undiagnosed and untreated.

The most clinically relevant non-criteria antibodies include:

  • Anti-Phosphatidylserine/Prothrombin Antibodies (aPS/PT): These are among the most studied non-criteria antibodies. They target a complex formed by the phospholipid phosphatidylserine and the clotting protein prothrombin. For obstetric APS specifically, aPS/PT of both IgG and IgM isotypes showed a significant and independent association with pregnancy morbidity.

  • Anti-Phosphatidylserine Antibodies (aPS): Phosphatidylserine is a phospholipid normally hidden on the inner surface of cell membranes. When cells are damaged or undergoing programmed death, phosphatidylserine becomes exposed on the outer surface. Antibodies against phosphatidylserine can interfere with trophoblast development and invasion — the very processes needed for the embryo to establish itself in the uterine wall.

  • Anti-Phosphatidylethanolamine Antibodies (aPE): Phosphatidylethanolamine is one of the most abundant phospholipids in cell membranes. In some patients, aPE may be the only antiphospholipid antibody detected — making it particularly important in cases where all other tests are negative. aPE antibodies are measured in IgG, IgM, and IgA isotypes.

  • Anti-Phosphatidylcholine Antibodies (aPC): Phosphatidylcholine is the most abundant phospholipid in cell membranes. Although less studied than some other non-criteria antibodies, anti-phosphatidylcholine antibodies have shown significant clinical associations. The addition of aPC IgG/IgM/IgA testing to standard criteria antibodies has been shown to significantly increase diagnostic sensitivity and accuracy.

  • Anti-Phosphatidylinositol Antibodies (aPI): Phosphatidylinositol is an anionic (negatively charged) phospholipid found in most cell membranes. It is well characterized as an antigen in APS. Anti-phosphatidylinositol IgG antibodies have been significantly associated with preeclampsia, premature birth, and arterial thrombosis.

  • Anti-Phosphatidylglycerol Antibodies (aPG): Phosphatidylglycerol is a phospholipid found in cell membranes and is a precursor to cardiolipin. A systematic review and meta-analysis of women with recurrent implantation failure found that anti-phosphatidylglycerol antibodies were strongly associated with implantation failure. These were among the strongest associations found for any non-criteria antibody in the context of IVF failure.

  • Anti-Phosphatidic Acid Antibodies (aPA): Phosphatidic acid is another anionic phospholipid found in cell membranes. Along with phosphatidylserine and phosphatidylinositol, it is well characterized as an antigen in APS. Some investigators have suggested that testing for aPA antibodies may help identify women with recurrent pregnancy loss.

Why Non-Criteria Antibodies Matter

A retrospective study of over 1,500 pregnant women with a history of miscarriage found that positive non-criteria antibodies were independently associated with adverse pregnancy outcomes (OR 1.62) and fetal loss (OR 1.44). Women with multiple positive non-criteria antibodies had even worse outcomes — with adverse outcome rates of 77.8% in the multiple-positive group compared to 37.0% in the single-positive group.

How Antiphospholipid Antibodies Harm Pregnancy: The Reproductive Immunology Perspective

For many years, doctors believed that antiphospholipid antibodies caused pregnancy loss primarily through blood clots in the placenta. While clotting is part of the picture, the damage goes far beyond simple thrombosis. Antiphospholipid antibodies attack pregnancy through multiple mechanisms simultaneously:

  • Direct Damage to Trophoblast Cells: The trophoblast is the outer layer of the embryo that develops into the placenta. Antiphospholipid antibodies bind directly to trophoblast cells, impairing their ability to grow, invade into the uterine wall, and migrate — all essential steps for establishing a healthy placenta. They also increase trophoblast cell death and reduce the secretion of hCG, the hormone that sustains early pregnancy.

  • Complement Activation: Antiphospholipid antibodies activate the complement system — a powerful arm of the immune system that amplifies inflammation. This triggers a cascade that recruits inflammatory cells to the placenta and damages placental tissue. The PROMISSE study demonstrated that elevated complement activation as early as 12–15 weeks of pregnancy was strongly predictive of adverse outcomes in women with these antibodies.

  • Disruption of Immune Tolerance: A healthy pregnancy requires the mother’s immune system to accept the embryo rather than attack it. Antiphospholipid antibodies disrupt this tolerance by causing dysfunction of uterine immune cells — including natural killer cells and macrophages — and driving a pro-inflammatory environment that undermines placental development.

  • Impaired Blood Vessel Remodeling: The small spiral arteries in the uterine wall must widen to deliver adequate blood to the placenta. Antiphospholipid antibodies interfere with this process, creating an anti-angiogenic imbalance similar to what is seen in preeclampsia.

  • Annexin V Displacement: Antiphospholipid antibodies strip the protective annexin V shield from trophoblast cell surfaces, exposing them to clotting factors and accelerating coagulation at the placental surface.

The Obstetric Criteria: What Pregnancy Complications Are Associated With APS?

The official obstetric criteria for APS include:

  • One or more unexplained deaths of a structurally normal fetus at or after 10 weeks of gestation.

  • One or more premature births of a structurally normal baby before 34 weeks due to severe preeclampsia, eclampsia, or placental insufficiency.

  • Three or more unexplained consecutive spontaneous pregnancy losses before 10 weeks of gestation (after excluding chromosomal, anatomical, and hormonal causes).

Non-Criteria Obstetric Manifestations

There are also pregnancy complications that are associated with antiphospholipid antibodies but do not meet the strict classification criteria. These are called “non-criteria obstetric APS” and include:

  • Two unexplained pregnancy losses (rather than three)

  • Three non-consecutive pregnancy losses

  • Late preeclampsia or eclampsia without severe features

  • Recurrent implantation failure during IVF

  • Placental insufficiency without meeting the strict criteria for preterm delivery before 34 weeks

These non-criteria presentations are increasingly recognized as clinically significant, and many experts believe they deserve evaluation and, when appropriate, treatment.

Seronegative APS: When Standard Tests Are Negative But the Problem Is Real

Some women present with all the clinical features of APS — recurrent pregnancy losses, placental complications — but test persistently negative for all three criteria antibodies. This is called seronegative APS (SN-APS).

Seronegative APS does not mean the antibodies are absent. It may mean that the current standard tests are not detecting them. In many of these patients, non-criteria antibodies — such as aPS/PT, anti-phosphatidylethanolamine, anti-phosphatidylcholine, anti-phosphatidylinositol, anti-phosphatidylglycerol, or anti-phosphatidic acid — may be present and contributing to the problem.

In one large study, up to 60.9% of seronegative APS patients were identified by at least one non-criteria antibody. Eight out of nine seronegative APS patients in another study were positive for at least one non-criteria antibody when a comprehensive panel was used.

This is why a comprehensive antiphospholipid antibody panel — testing for both criteria and non-criteria antibodies — can be valuable in women with unexplained recurrent pregnancy loss, particularly when standard testing is negative.

Testing: What Should Be Measured?

A comprehensive antiphospholipid antibody evaluation may include:

Criteria Antibodies (Standard Testing)

  • Lupus anticoagulant (LA)

  • Anticardiolipin antibodies (aCL IgG and IgM)

  • Anti-β2-glycoprotein I antibodies (anti-β2GPI IgG and IgM)

Non-Criteria Antibodies (Extended Panel)

  • Anti-phosphatidylserine/prothrombin antibodies (aPS/PT IgG and IgM)

  • Anti-phosphatidylethanolamine antibodies (aPE IgG, IgM, and IgA)

  • Anti-phosphatidylcholine antibodies (aPC IgG, IgM, and IgA)

  • Anti-phosphatidylinositol antibodies (aPI IgG, IgM, and IgA)

  • Anti-phosphatidylglycerol antibodies (aPG IgG, IgM, and IgA)

  • Anti-phosphatidic acid antibodies (aPA IgG, IgM, and IgA)

  • Anticardiolipin IgA antibodies (aCL IgA)

  • Anti-β2GPI IgA antibodies

Important Notes About Testing:

  • Criteria antibodies must be confirmed on two separate occasions at least 12 weeks apart to establish persistent positivity.

  • Non-criteria antibody assays are not yet fully standardized across all laboratories, which is one reason they have not been included in the official classification criteria. However, their clinical relevance is supported by a growing body of evidence.

  • Results should always be interpreted by a specialist experienced in reproductive immunology, in the context of your complete clinical history.

What This Means for You

If you have experienced recurrent pregnancy loss, unexplained fetal death, severe early preeclampsia, or repeated IVF failures, antiphospholipid antibodies may be playing a role — even if your initial standard tests were negative.

  • APS is Treatable: Antiphospholipid syndrome is the most important treatable cause of recurrent pregnancy loss.

  • Standard Testing is Limited: Standard “criteria” antibody testing captures only part of the picture. Non-criteria antibodies — including anti-phosphatidylserine/prothrombin, anti-phosphatidylcholine, anti-phosphatidylinositol, anti-phosphatidylglycerol, anti-phosphatidic acid, and anti-phosphatidylethanolamine antibodies, as well as IgA isotypes — are increasingly recognized as clinically significant and may explain cases previously labeled “unexplained.”

  • The Damage Involves the Immune System: The damage caused by antiphospholipid antibodies goes far beyond blood clots. These antibodies directly attack the placenta, activate the complement system, disrupt immune tolerance, and impair blood vessel development — all through immune-mediated mechanisms.

  • Therapy is Highly Effective: Treatment is effective. With appropriate therapy, the majority of women with APS can achieve successful pregnancies.

  • Specialized Evaluation Offers Answers: A comprehensive evaluation by a reproductive immunology specialist — including both criteria and non-criteria antibody testing — can uncover treatable causes that standard testing misses.

 

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Other Autoantibodies

Other Autoantibodies

Several autoantibodies will be tested such as ANA, anti-DNA, anti-SCL70, anti-Histones, anti-TPO, and others. Many autoimmune diseases have been associated with reproductive failures such as repeated miscarriages (or recurrent pregnancy loss) and multiple implantation failures. Immune therapy is used to suppress those autoantibodies.

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