The role of gamma/delta T cells in progesterone-mediated immunomodulation during pregnancy: a review.
OBJECTIVE
To determine if pregnancy is recognized by the immune system and if inadequate recognition of fetal antigens might result in failed pregnancy.


METHODS
Review of literature and current data.


RESULTS
In the decidua gamma/delta TCR positive cells significantly increase in number. A subset of gamma/delta T cells reacts with nonpolymorphic Class I or Class I like molecules. Trophoblast recognition is mediated by the V gamma 1 subset which recognize a conserved mammalian sequence on the trophoblast. Almost all gamma/delta T cells in the decidua are activated and use the V delta 1 chain, whereas the majority of human peripheral gamma/delta lymphocytes 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 the other hand, those of recurrent aborters use the V gamma 9V delta 2 combination. 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) activity. In the presence of progesterone, activated lymphocytes synthesize the progesterone induced blocking factor (PIBF), which inhibits NK activity and exerts an anti abortive effect in vivo. Decidual CD56+ and gamma delta+ cells are to a high extent the same population.


CONCLUSIONS
All decidual CD56+ cells express PIBF, thus it cannot be excluded that local production of this substance contributes to low decidual NK activity and thus to the success of the pregnancy.
Szekeres-Bartho
J
J
Department of Microbiology, University Medical School of Pecs, Hungary.
Barakonyi
A
A
Polgar
B
B
Par
G
G
Faust
Z
Z
Palkovics
T
T
Szereday
L
L
D003656:Decidua / Q000276:immunology*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000096:biosynthesis; D011374:Progesterone / Q000494:pharmacology*; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000378:metabolism*; D013491:Suppressor Factors, Immunologic; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D014327:Trophoblasts / Q000276:immunology*
C110058:PIBF1 protein, human; D011257:Pregnancy Proteins; D016692:Receptors, Antigen, T-Cell, gamma-delta; D013491:Suppressor Factors, Immunologic; D011374:Progesterone