Clinical significance
The role of antisperm antibodies in preventing sperm from penetrating cervical mucus has been clearly defined by several authors. For example, Moghissi found antisperm antibodies in the cervical mucus of 25% of the women in 172 infertile couples, while 13% of the women in the same group had antisperm antibodies in their blood. In another study, 64% of 66 couples without significant amounts of antisperm antibodies on the sperm surface showed adequate sperm motility in cervical mucus, compared with 26% of 122 couples with sperm-bound antisperm antibodies (American Journal of Obstetrics & Gynecology). The presence of antisperm antibodies in a woman’s blood is not closely related to their presence in cervical mucus, and in general the clinical significance of antisperm antibodies in the blood of men and women is controversial.
Mechanism
Sperm are “foreign” to the body because, unlike all other cells, they contain only half the set of chromosomes (23 chromosomes compared with the normal 46), i.e. they are haploid rather than diploid. When sperm come into contact with the blood, they can therefore trigger an immune reaction consisting of the production of antisperm antibodies. For this very reason, spermatogenesis (the production of sperm) takes place behind the “immune barrier” provided by the testes.
Under normal conditions the testes contain a basement membrane, the blood–testis barrier, which acts as a protective layer preventing contact between immune cells and sperm within the male reproductive tract. This barrier can break down as a result of trauma to the reproductive tract, so that immune cells come into contact with the sperm, attacking and destroying them.
Immunological infertility
Immune system disorders can lead to reproductive failure at various stages of the reproductive process: unexplained infertility, repeated failure of in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI), and recurrent miscarriage. The immune system is made up of immune cells and cell products (cytokines), and among the many immune cells, two in particular are associated with infertility, recurrent embryo implantation failure and miscarriage: CD56 cells (natural killer cells), which produce toxic cytokines such as tumour necrosis factor alpha (TNF-α), and CD19 cells, which produce antibodies against hormones such as human chorionic gonadotrophin (hCG), progesterone and so on. Antibodies are proteins produced by B lymphocytes, a type of immune cell; they circulate in the blood and tissues and normally protect the body against invasion by foreign agents such as viruses and bacteria; in some cases, however, the body may develop antibodies against its own cells.
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