The role of gamma/delta T cells in progesterone-mediated immunomodulation during pregnancy: A review

PROBLEM: To determine if pregnancy is recognized by the immune system and i f inadequate recognition of fetal antigens might result in failed pregnancy , METHOD OF STUDY: Review of literature and current data. RESULTS: In the decidua gamma/delta TCR positive cells significantly increa se in number. A subset of gamma/delta T cells reacts with nonpolymorphic Cl ass I or Class I like molecules. Trophoblast recognition is mediated by the Vyl subset which recognize a conserved mammalian sequence on the trophobla st. Almost all gamma/delta T cells in the: decidua are activated and use th e V delta 1 chain, whereas the majority of human peripheral gamma/delta lym phocytes expresses V gamma 9/V delta 2 TCR. Peripheral gamma/delta T cells of healthy pregnant women preferentially use V gamma V delta 1 chains, on t he other hand, those of recurrent aborters use the V gamma 9V delta 3 combi nation. Signaling via the V gamma 1.4V delta 1 receptor induces a Th2. type response, whereas activation of the lymphocytes via the V gamma 9V delta 2 receptor results in increased IL-12 production and natural killer (NK) act ivity. In the presence of progesterane, activated lymphocytes synthesize th e progesterone induced blocking factor (PIBF), which inhibits NK activity a nd exerts an anti abortive effect in vivo. Decidual CD56 + and gamma delta + cells are to a high extent the same population. CONCLUSION: All decidual CD56 + cells express PIBF, thus it cannot be exclu ded that local production of this substance contributes to low decidual NK activity and thus to the success of the pregnancy.