PROBLEM: The number of perforin (P)-positive cells in decidua of pregnancy is larger than that observed in any other pathological condition. The aim was to investigate the distribution and the phenotype of P+ cells.
METHOD: Decidual tissue was obtained from the first trimester vaginal termination of pregnancy. Tissue distribution of P+ cells was analyzed by immunohistochemistry. The method for simultaneous measurement of P and cell surface is presented.
RESULTS: There is no difference in number and distribution of P+ cells between decidua basalis (DB) and decidua parietalis (DP). The percentage of P+ decidual lymphocytes (DL) is two times higher than in peripheral blood lymphocytes (PBL) (55% vs. 27%), and the prevalent phenotype is CD3− CD4− CD8− CD2+ (95%) CD11c+ (68%) and CD56+ (82%). CD56bright+ DL are also Pbright+ and this is the largest DL subpopulation (42.4% DL). Two different subpopulations of CD8+ DL exist: 1) CD8bright+, which are CD3+ CD56− P− and 2) CD8dim+, which are CD3− CD56+ P+.
CONCLUSION: P expressing DL are prevalently nonclassical NK cells (CD16−) with low cytolytic activity but fully equipped with potent cytolytic machinery (pbright+). There are no classical cytotoxic lymphocytes (CTL) (CD3+ CD8+ P+) in the decidua, and all CD8+ P+ cells are CD3− CD56+. The number of P+ cells is even higher in DP in the vicinity of noninvasvie trophoblast, than in DB.