Microbiology/Genetics

What Launches Your Antibodies Against the Sperm?

Scientists have decoded a mechanism of the immune infertility

By Stefan Anitei, Science Editor

13th of September 2007, 18:26 GMT

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Contaminants, stress and other factors brought by modern life are blamed for the increasing rates of infertility, but few have heard about immune infertility, a quite common cause of couple sterility.

Immune infertility is amongst the 80 autoimmune disorders discovered so far and the best known are Multiple Sclerosis and Type 1 Diabetes. This reproductive disease installs in both men and women, causing their immune systems to attack sperm cells.

A recent research at the University of Virginia Health

System has found a new human protein, radial spoke protein 44 (RSP44), because of which the immune system attacks sperm. When put in the blood, RSP44 made infertile men synthesize antisperm antibodies (ASA).

"We've spent several years looking for sperm molecules that evoke antibody responses in humans. The identification of RSP44 gives us additional insight into immune infertility and may prove useful in diagnosing the disorder in a subset of men. RSP44 will likely not be a dominant antigen in everyone." said Dr. John C. Herr, director of UVa's Center for Research in Contraceptive and Reproductive Health.

RSP44 is encountered in all men, being located in the sperm tail at the middle of a structure called axoneme. The axoneme contains microtubules that determine the sperm movement. Humans of both genders have RSP44 in hair-like strands, called cilia in the respiratory ducts and bronchioles of their lungs, the ventricles of their brains and the lumens of their thyroid gland.
Until this discovery, scientists thought that ASA only attacked the surface of the sperm membrane.

"Because RSP44 is located in the heart of the axoneme, it doesn't appear to be directly involved in ASA binding at the sperm membrane. Identifying RSP44 as an antigen in several individuals indicates it may serve as a useful biomarker of the anti-sperm response. There may be mechanisms underlying infertility that are yet to be discovered." said lead author Dr. Jagat Shetty.

Women experiencing immune infertility have ASA in their reproductive ducts, that kill the sperms by piling them and destroying their membranes. Antisperm antibodies also cover receptors that cause sperm-egg binding and fertilization. Up to 15 % of sterility cases in women are due to ASA. There are cases when ASA caused anaphylactic shock in women following insemination.

Immune infertility in men has several causes, like vasectomies. Following a vasectomy, the sperms that cannot be released outside are "digested" by ASA. ASA can persist for years in the bloodstream of vasectomized men even when they underwent the reversed procedure (vasovasostomy), causing decreased fertility. Therapies like sperm washing and intra-cytoplasmic sperm injection are used to treat patients suffering from this disease.

TAGS:

immune | fertility | sterility | sperm

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