Antisperm antibodies (ASA)
What are antibodies?
The human body has an immune system (‘Army’ of the body) and its job is to neutralise any threats to the body from invaders such as bacteria, viruses or even cancer cells. To neutralise the offending agent it has to recognise the antigen, a specific part on the agent. The immune system produces specialised proteins called immunoglobulins (designated as Ig), that are produced by the cells of the immune system.
What are antisperm antibodies? How do they form?
A man’s blood and sperm do not come in contact with each other because of a barrier system (Testis-blood barrier). In testis, specialized cells known as Sertoli cells form this barrier (Similar barrier system exists elsewhere in the brain: called Blood-brain barrier). Any disturbance to this system physical, chemical, infection, inflammation and trauma could break the barrier and sensitize the immune system to sperm. Sometimes infection or inflammation in other parts of male genital system could produce the antibodies. The ‘soldiers’ in the immune system are white blood cells called lymphocytes (B and T lymphocytes). The origins of ASA are uncertain – it is not whether they are produced by the body or the testis.
Why does ASA interfere with fertilisation?
It is well known that naturally occurring antibodies to eggs and sperm can cause problems with fertility. The antibodies bind to the proteins (antigens) on the sperm’s head, midpiece or tail. ASA could cause sperm inaction in 3 ways:
- agglutination (clumping and sticking together) reducing the number of sperm penetrating cervical mucus;
- immobilization of sperm – sperm is unable to move
- spermatotoxic – causing loss in viability of the sperm
In some patients antibodies may be found in the blood and these are known as circulatory antibodies. High levels of antibodies in the blood do not invariably mean that the antibodies will find their way to the semen where they can affect the sperm. Antibodies may also interfere with egg penetration and sometimes prevent the sperm from swimming through the cervix.
It is highly unlikely that pregnancy can be achieved naturally or by intrauterine insemination in presence of ASA.
How is ASA detected?
The ASA are measured by mixed antiglobulin reaction (MAR test) test on the sperm. This is usually done at the time of semen analysis.
Is it possible to have sperm immunity developing in women?
Sometimes sperm antibodies are also found in women, the presence of which reduce the likelihood of conception naturally or by conception IVF in humans. This has also been confirmed in experimental setting. The exact cause of sperm antibodies women is unknown.
Are there any reference values for ASA?
There are currently no reference values for antibodies. The WHO manual refers to a threshold of 50% motile sperm with adherent particles.
Mr Vinod Nargund is a Consultant Urological Surgeon specialising in Urological cancer, male sexual and fertility problems. He was trained in Urology at the City Hospital Belfast, the Royal Infirmary Bradford and the Churchill and John Radcliffe Hospitals in Oxford. You can view all of his qualifications on his biography page.