The immune microenvironment of the hydatidiform mole.

Gestational trophoblastic diseases (GTDs) are a heterogeneous group of lesions, the most frequent being the hydatidiform mole (HM). HMs are usually cured after surgical treatment or after chemotherapy in the case of a persistent trophoblastic activity. Immunotherapy could be an interesting alternative as a first-line or second-line treatment. However, only a few studies have explored the immune microenvironment of HMs. In the present retrospective study including 19 complete and 17 partial moles, we examined the composition of the immune cell microenvironment by immunohistochemistry using the following antibodies: CD4, CD8, CD56, PD-L1, S100, CD83, CD207, CD123, CD1a, CD11c, CD163, PAX5, and MUM1. In the decidual cells compartment, CD11c+ cells were the predominant population, followed by CD4+ cells, CD56+ NK cells, CD163+ macrophages, and CD8+ T lymphocytes.In the endometrial glands compartment, CD11c+ cells were the predominant population, followed by CD4+ cells, CD56+ NK cells, and CD8+ T lymphocytes. In the villi compartment, the predominant immune cells were CD4+ cells, followed by CD163+ macrophages and CD11c+ cells. Statistically significant differences were observed between partial and complete moles in all three compartments. The immune microenvironment of HMs is immunosuppressive, but it differs between complete and partial moles, the latter having a higher infiltrate of cells with phenotypes suggestive of immunosuppressive activities.