Antisperm Antibodies

How antisperm antibodies form

Sperm are made after puberty, long after the immune system has learned what belongs to the body. In men, a protective blood-testis barrier keeps sperm hidden from immune cells. When that barrier is damaged, sperm proteins are exposed, and the immune system may make antibodies against them.

Antibodies can attach to the sperm head, midpiece or tail:

• Head-bound antibodies can block binding to and penetration of the egg.
• Tail-bound antibodies reduce swimming and penetration of cervical mucus.
• Antibodies can cause sperm to stick together (agglutination).

Causes and risk factors

In men

• Vasectomy: most men develop antisperm antibodies after vasectomy. This matters mainly for those who later have a reversal.
• Testicular trauma or torsion
• Infections: epididymitis, orchitis including mumps, and prostatitis
• Surgery in the scrotum or groin, such as hernia repair or biopsy
• Varicocele and blockage of the ducts
• Undescended testicles (cryptorchidism)

In women

Women can develop antibodies in cervical mucus or blood after exposure to sperm, possibly linked to genital tract inflammation or infection. Their importance for female fertility is less clear and testing women is rarely recommended.

How common are they?

Antisperm antibodies are found in a minority of infertile men, roughly 5 to 10% in many studies, and in a small proportion of fertile men too. Their presence does not always cause infertility. The level matters: lower levels often have no effect.

Testing

Antisperm antibody testing is not part of every infertility workup. Guidelines suggest testing when a semen analysis shows:

• sperm clumping (agglutination)
• poor motility without another explanation
• a history of risk factors such as vasectomy reversal or testicular injury

Tests performed on fresh semen:

• Mixed antiglobulin reaction (MAR) test
• Immunobead test

A result is usually considered clinically significant when 50% or more of motile sperm are coated. Blood tests for antisperm antibodies are less useful in men.

The full fertility evaluation for a couple includes the woman's ovulation, tubes and uterus, because infertility often has more than one cause. See male factor infertility and female infertility.

Treatment

Assisted reproduction

• Intrauterine insemination (IUI): washed sperm are placed directly in the uterus, bypassing cervical mucus. It may help mild cases.
• IVF with intracytoplasmic sperm injection (ICSI): a single sperm is injected directly into each egg, bypassing most effects of antibodies. ICSI results in men with antisperm antibodies are similar to those without, and it is the most effective treatment for significant levels.

Other approaches

• Corticosteroids to suppress antibody production have been tried but have limited evidence and significant side effects (such as bone damage to the hip). They are rarely recommended now.
• Sperm washing techniques can remove some surface antibodies.
• Sperm retrieval directly from the testis or epididymis, where sperm may carry fewer antibodies, is sometimes used with ICSI.
• Treating underlying infection where present.

Outlook

Many couples with antisperm antibodies conceive, especially when levels are low. For those with high levels, IVF with ICSI gives pregnancy rates comparable to other couples undergoing the same treatment.

Frequently asked questions

What causes antisperm antibodies?

In men, they form when the barrier that hides sperm from the immune system is broken, most commonly after vasectomy or its reversal, testicular injury or torsion, infections such as epididymitis or mumps orchitis, and surgery in the scrotum or groin.

Do antisperm antibodies cause infertility?

They can, but not always. Low levels often have no effect. Higher levels, especially when half or more of the moving sperm are coated, can reduce sperm movement and the ability to fertilize an egg, lowering the chance of natural conception.

How are antisperm antibodies tested?

The usual tests are the mixed antiglobulin reaction (MAR) test or the immunobead test on a fresh semen sample. They are typically ordered when a semen analysis shows clumping or poor motility, or after a vasectomy reversal.

Can antisperm antibodies go away?

Levels can fall over time, particularly after an infection resolves, but they often persist, especially after vasectomy. Steroid treatment to lower them has limited success and notable side effects, so most couples are offered assisted reproduction instead.

Can women have antisperm antibodies?

Yes, women can have antisperm antibodies in cervical mucus or blood, but their role in female infertility is uncertain and routine testing is not recommended. If present, IUI or IVF can bypass the cervical mucus.