Tubal abortions but not viable tubal pregnancies are characterized by an increased number of CD8 + T cells

To examine immune cell phenotypes in viable tubal pregnancies (VTP) and in tubal abortions (TA).Paraffin-embedded specimens of VTP (n=7) and ongoing TA (n=6) were double-stained for cytokeratin for trophoblast as well as for CD45, CD3, CD8, CD68 and CD20 for immune cell phenotypes. In all cases, the amniotic sac was detected by ultrasound. Histological examination showed no evidence of necrosis within the tissues included in this study. Quantification of the subpopulations was performed in each slide by two independent examiners in five areas (0.085 mm2 each) of the invasion zone as marked by cytokeratin-positive stromal extravillous trophoblast (EVT) cells. For statistical analysis, the non-parametric two-tailed t-test was used (p<0.05).The differences in the number of CD45(+), CD68(+) and CD20(+) cells was significant (p=0.0423, p=0.0469 and p=0.0494, respectively); however, the number of CD3(+), and among those the number of CD8(+) cells, was approximately eight-fold higher in TA than in VTP (p<0.0001 and p=0.0012, respectively).The unequal distribution of CD8(+) cells in VTP and TA suggests a significant role of this immune cell phenotype in the further outcome of a tubal pregnancy either to an abortive or a viable, potentially life-threatening, entity.