Problem: Pregnancy has been considered as a model of successfully controlled tissue invasion where trophoblast cells infiltrate the maternal decidua without being rejected or without destroying the tissue. In choriocarcinoma (CC) and hydatidiform mole (HM), a dysregulation of invasive (malignant/benign) trophoblast cells is present. Immunocompetent cells (IC) are known to be involved in rejection pathways of malignant cells and can also be identified in early pregnancy decidua. The aim of the present study was to identify the phenotype of IC in decidua of women with normal pregnancy (NP), CC and HM.
Methods: Immunocompetent cells were detected by immunohistochemistry in decidual tissue from first trimester NP (n = 10), CC (n = 12) and HM (n = 11) using antibodies against CD8+, CD3+, CD56+, CD68+ cell surface markers and mast cell tryptase (MCT). A scaled eye piece was used for cell counting to obtain semiquantitative results. Statistical analysis was performed using Wilcoxon rank/Mann–Whitney tests.
Results: We observed a significantly increased number of lymphocytes positive for CD8, CD3 and MCT positive granulocytes in CC and HM compared with the samples from NP (all P ≤ 0.001). Lymphocytes positive for natural killer (NK) cell marker CD56 were significantly decreased in CC and HM versus NP (P ≤ 0.001). The number of CD68 positive cells (macrophages) were not significantly different among the tissue pools.
Conclusion: The increase of CD8/CD3 T cells and mast cells in CC and HM and the decrease of CD56 cells, compared with NP, suggests the necessity of a balance between T and NK cells in controlling trophoblast invasion.