Elevated expression of activation molecules by decidual lymphocytes in women suffering spontaneous early pregnancy loss

The purpose of this study was to investigate, quantify and compare the expression of activation markers by decidual leukocytes in sporadic spontaneous early pregnancy loss and apparently normal first trimester human pregnancy. Decidua was obtained from 18 therapeutic abortions and 20 sporadic spontaneous abortions at 8–12 weeks gestational age. Cryostat sections were labelled by the avidin–biotin complex–peroxidase method using monoclonal antibodies specific for CD45, CD56, CD3, human leukocyte antigen (HLA) DR, CD69, CD25 and very late antigen (VLA)1. Positive cells were quantified and the results were analysed using the Mann–Whitney statistical test. Significantly increased numbers of CD69-positive and CD25-positive cells were detected in spontaneous abortion decidua, when compared with therapeutic abortion decidua. Approximately 50% of women experiencing spontaneous miscarriage also contained significantly elevated numbers of HLA DR-positive cells within decidua. Double immunohistochemical labelling studies demonstrated that the CD25-positive and CD69-positive cells in spontaneous abortion decidua were CD3-positive T cells rather than CD56-positive granulated lymphocytes. Immunological dysfunction within endometrium may account for a proportion of sporadic spontaneous abortions.