Autoimmune Sperm Warfare
Warring Immune System
While most of us have never heard of immune infertility, the condition prevents many couples from conceiving. Immune infertility is a kind of autoimmune disorder, one of 80 such conditions including Lupus Erythematosus, Multiple Sclerosis, and Type 1 Diabetes. Both men and women are affected by this reproductive disorder, which causes the immune system to wage a personal and internal war on sperm.
New Human Protein
Researchers at the University of Virginia Health System have found a new human protein, radical radial spoke protein 44 (RSP44). This finding may help pinpoint the molecules that are responsible for assisting an impaired immune system in attacking sperm. The study showed that exposing infertile men to RSP44 causes them to produce antisperm antibodies (ASA).
The scientists believe that RSP44 belongs to a well-preserved and long-standing gene family. The protein can be found in all males and lives in the sperm tail in the center of a structure known as the axoneme. The protein collects around small moving platforms known as microtubules, central factors in sperm motility.
The discovery of the new protein changes scientific thought on the causes of immune infertility. Until now, it was believed that antisperm antibodies only targeted the outer surface, or membrane of the sperm. Researchers are now exploring the idea that there may be other mechanisms underlying infertility that have yet to be discovered.
"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," states Dr. Jagat Shetty, lead author of the University of Virginia paper. "There may be mechanisms underlying infertility that are yet to be discovered."
Women who have immune infertility produce ASA in their reproductive tracts. The antibodies cause sperm to cluster, and then kills them by poking holes in their membranes. ASA also coats the receptors that are responsible for both binding sperm to eggs and for fertilization.
Research suggests that 12-15% of unexplained female infertility is linked to ASA. In rare cases, women go into anaphylactic shock upon insemination. In men, immune infertility can be triggered by many factors, one of which is vasectomy. After vasectomy, the body stops releasing sperm and instead produces antibodies to surround and clear sperm from the body. Since these antibodies may be produced for several years, they can prevent restored fertility in men who have vasectomy reversals or vasovasostomy.
Couples with ASA may benefit from sperm washing or intra-cytoplasmic sperm injections.