Spermatogenesis is considered to be a highly complicated process, tightly regulated by various factors, either local or paracrine ones. Additional challenge stems from the fact that the process starts at the puberty and newly appearing proteins cannot be recognized as self components by already formed immune system. To protect developing gamete precursors from an autoimmune attack, the complicated multifactorial system with acting numerous mechanisms has been established during evolution. Thus very precisely regulated environment in the male gonad was created and maintained. Testis has been considered as “immune privileged” site.

Systemic as well as paracrine factors are involved in active tolerance within the male gonad establishing the critical balance between the two principal goals: to provide immunologically neutral zone for gametogenic cells and to provide the essential defense against pathogens. Factors implicated in these testicular functions are (among the others): pro- and anti-imflammatory cytokines (e.g. IL-1, IL18, TGFβ), apoptotic mediators, androgens, MHC antigens etc., some of them still remain to be elucidated.