The female immune system DOES attack sperm as foreign cells!
Not only is that but the vaginal pH too acid for sperm cells to survive! It takes the speed of the ejaculate, the less acid mean of the sperm and the speed of the sperm cells to travel their journey to be able to achieve the ovule – and during that travel there are immune cells (and antibodies, complement molecules, etc.) that try to stop the ”voyage” of the sperm cell!
To the sperm cell it’s really a run for the first place and a run for survival!
Most of us have never heard of immune infertility, yet it prevents many prospective parents from conceiving.
Immune infertility is one of 80 autoimmune disorders, a group that includes better-known diseases like Multiple Sclerosis and Type 1 Diabetes. This reproductive disorder affects both men and women, causing their immune systems to wage war on sperm.
A recent discovery at the University of Virginia Health System may help pinpoint what molecules assist the immune system in attacking sperm. In the July 2007 issue of Gene, UVa researchers reported finding a new human protein, radical radial spoke protein 44 (RSP44). Exposure to RSP44 caused serum from infertile men to produce antisperm antibodies (ASA) in their serum. (ASA).
“We’ve spent several years looking for sperm molecules that evoke antibody responses in humans,” says Dr. John C. Herr, director of UVa’s Center for Research in Contraceptive and Reproductive Health. “The identification of RSP44 gives us additional insight into immune infertility and may prove useful in diagnosing the disorder in a subset of men. Sperm proteins like RSP44 will likely not be a dominant antigens in everyone.”
Researchers believe that RSP44 belongs to a highly conserved and ancient gene family. It can be found in all men, residing in the sperm tail at the center of a structure known as the axoneme. There, it clusters around microtubules involved in sperm movement. Both men and women have RSP44 in hair-like strands, called cilia, in the bronchioles of their lungs, the ventricles of their brains and the lumens ofcolloids in their thyroid gland.
The discovery of RSP44 also promises to broaden scientific thinking about the causes of immune infertility. Until now, researchers believed that ASA only targeted 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,” notes Dr. Jagat Shetty, lead author of the UVa paper. “There may be mechanisms underlying infertility that are yet to be discovered.”
Women with immune infertility produce ASA in their reproductive tracts. These antibodies neutralize sperm by clumping them together and poking holes in their membranes. ASA also coats over receptors involved in sperm-egg binding and fertilization.
An estimated 12 to 15 percent of unexplained infertility in women is linked to ASA. In rare cases, these antibodies have caused women to go into anaphylactic shock upon insemination.
In men, immune infertility has several causes, including vasectomies. After a vasectomy, the body can no longer release sperm and produces antibodies to help engulf and clear them. ASA persists for years in the circulation of vasectomized men and may cause reduced fertility in those who have the procedure reversed (vasovasostomy).
Several therapeutic procedures available through UVa, such as sperm washing and intra-cytoplasmic sperm injection, have proven beneficial to patients with ASA.
Mating is a dangerous time for the female because harmful bacteria can enter the reproductive tract along with seminal fluid. However, Fazeli’s study shows that oviduct cells can differentiate between alien proteins arriving with bacteria and those of her mate and prevent the immune system attacking the latter.
The female response not only protects sperm cells from attack it also helps them survive the wait until the egg or oocyte arrives. ’Sperm cells are very sensitive to heat and in vitro they would be completely destroyed within four or five hours at the temperature found within the reproductive tract. But by nourishing and protecting them in the oviduct they can be kept alive for several days,’ Fazeli explains.
For example, one of the proteins – the fibrinogen A-alpha chain – prevents the sperm cell being destroyed by immune cells, while another – hyaluronidase – digests the protective layer of hyaluronic acid around the egg to aid fertilisation.
It’s just that, for the most part, most sperm cells don’t come into contact with her immune cells; they travel through the vagina, through the uterus, and up into the fallopian tubes, where they’re not directly exposed to her blood or lymph (which is where most immune cells not found in the brain reside).
But yes, it is possible for a woman to mount a strong enough immune response that she cannot become pregnant, or has difficulty becoming pregnant.
