Seminal Plasma, Immune System and Fertility

One of the most important male factors for a successful preg-nancy is seminal plasma (SP). SP provides a rich environment for a successful pregnancy and contains several different pro-teins originating from the testis, epididymis and male acces-sory glands. In efforts to ensure safe passage, multiple gene ex-pression pathways are initiated in female epithelial cells upon contact with seminal fluid. More than 700 genes found to be differentially expressed in ectocervical tissue after intercourse, most are involved in the presentation of pro-inflammatory an-tigens and the expression of cytokines and chemokines. The soluble immune components of seminal fluid modulate the ma-ternal response in such a way that pregnancy can progress. SP also promotes recruitment and activation of the immune cells, including macrophages, dendritic cells, and T cells. Moreover, SP plays a pivotal role in the induction of immune tolerance to paternal alloantigen through expanding the pool of induc-ible regulatory T (Treg) cells. These semen-induced changes in gene expression and resultant cellular response are known as the leukocyte reaction. Interestingly, SP also affects the sperm quality and functions before insemination. It means that SP can both stimulate and inhibit the capacity of the spermatozoa for fertilization. During the transit of the spermatozoa from the epididymis, sperm gain its motility and fertilizing capacities under the influence of proteins from the epididymal fluid, which can thereafter be observed in the SP and bind to the sperm sur-face. Understanding the role of SP in a normal pregnancy may provide new options for diagnosis and treatment of infertility.