Novel T cell receptor expression features in sperm and testis

Except from the myeloid in origin cells, ectopic expression of T-cell receptors (TCRs) was also detected in sperm and the female reproductive tract, which in conjunction with major histocompatibility complex (MHC) molecules suggested their involvement in mate choice. Following-up these observations and considering that MHC/TCR interactions could guide spermatozoa towards ovum, the present study aimed to delineate the presence of TCRs in sperm vis-à-vis cognate recognition and define such expression during spermatogenesis. Immunofluorescence experiments using fertile BALB/c males showed that despite the inbred origin of mice, all combinations of high (HI, >20 % expression) and low (LO, <5 % expression) TCRαβ and TCRγδ expression could be detected in equal distribution rates, followed by an inverse pattern of MHC expression. Samples TCRαβΗΙ did not express MHCI/II, but TCRαβLO/TCRγδHI samples showed increased expression of MHCII. High expression TCRαβ samples also expressed CD3e and CD4, but at lower than expected levels. In all cases, soluble TCRs and MHCs were detected by ELISA in the seminal fluid, where TCRαβ highly correlated with MHCI/II and TCRγδ with MHCI. Except from the classical α, β, γ and δ transcripts, RT-PCR experiments detected additional, not-yet identified products for α and γ genes. Fluorescent microscope analysis identified TCRαβ and TCRγδ expression in spermatozoa tail. Immunohistology and cell dissociation of testis also detected TCR expression during spermatogenesis. Apart from un-folding novel structural, functional and regulatory features of TCRs in non-T cells, the results favor the involvement of TCRs in male reproduction and could serve as diagnostic markers in unexplained infertility.