Evidence for a unique expression of CD4 on murine vaginal CD4(+) cells

Mucosal cell-mediated immunity (CMI) by CD4(+) T cells is postulated to be important for host defence against several vaginal pathogens. In addition t o the recognized phenotypic distinctions of resident vaginal T lymphocytes, we recently provided evidence by fluorescence-activated cell sorter (FACS) that murine vaginal CD4(+) T lymphocytes, are differentially recognized by two epitope-distinct anti-CD4 antibodies, suggesting that the CD4 protein on vaginal CD4(+) cells is atypically expressed. In the present study, we c onfirm this by FACS and immunohistochemistry under non-denaturing condition s using two additional anti-CD4 antibodies. However, positive immunohistoch emical staining of vaginal CD4(+) cells under denaturing conditions reveale d that the CD4 epitope in question is indeed present within the CD4 protein . Using reverse transcription polymerase chain reaction, amplification of C D3, T-cell receptor-beta (TCR-beta), and TCR-delta mRNA from lymph node and vaginal tissue, and CD4 mRNA from lymph node tissue was demonstrable. In c ontrast, amplification of CD4 mRNA from vaginal tissue, vaginal enriched ly mphoid cells, or a purified (FACS-sorted) population of vaginal-specific CD 4(+) cells using two distinct primer sets was not demonstrable. Altogether, our results provide evidence that the CD4 protein on vaginal CD4(+) T cell s is conformationally distinct compared with its systemic counterpart, eith er as a result of a unique CD4 mRNA sequence or from a stable interaction o f soluble CD4 with the surface of vaginal T cells.