Study on defense mechanism of the placenta and fetus against HTLV-I transmission from mother to fetus

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This study was done to investigate defense mechanisms of the placenta and fetus against human T-lymphotropic virus type I (HTLV-I) transmission from mother to fetus.Placentas and cord blood lymphocytes (CBL) were tested for HTLV-I infection.Apoptosis in the placentas was examined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling method. CD8, CD14, CD68-positive cells in the placentas were tested by immunohistochemistry. Co-cultivation of placental villous cells with an HTLV-I-infected cell line was performed. Epstein-Barr virus (EBV) transformation was performed in CBL.Eight of 16 (50%) placentas from HTLV-I-seropositive mothers were infected with HTLV-I.None of the CBL were infected. The incidence of apoptosis-positive cells in the HTLV-I-infected placentas was higher than those of HTLV-I-seronegative (p<0.05). CD8^+cells, CD14^+cells, and CD68^+cells were detected in the placentas. Placental macrophage-like cells had the capacity to phagocytose the HTLV-I-infected cells. Production of antibodies against HTLV-I was inducible by EBV transformation of CBL.It was suggested that the placenta served as a barrier to HTLV-I transmission from mother to fetus through an apoptosis-related defense mechanism, and that fetus itself had the capacity to protect HTLV-I infection, where HTLV-I-infection reached to fetal circulation.