THE INTERACTION OF SPERM CELLS WITH EXOGENOUS DNA - A ROLE OF CD4 ANDMAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II MOLECULES

Mouse epidydimal sperm cells have the spontaneous ability to take up e xogenous DNA, a part of which is further internalized into nuclei. We report here that sperm cells from MHC class II knockout mice have a re duced ability to bind DNA compared to sperm cells from wild-type anima ls. Spermatozoa from CD4 knockout mice are instead fully capable of bi nding exogenous DNA, yet lose the ability to further internalize it. M HC class II expression was not detected on sperm heads using monoclona l antibodies. In contrast, CD4 molecules were found on sperm heads by both immunofluorescence and Western blot analysis. Moreover, we show t hat nuclear internalization of exogenous DNA was prevented in wild-typ e sperm cells preincubated with anti-CD4 mAbs. These results support t he conclusion that CD4 and MHC class II molecules play distinct roles in the process of sperm/DNA interaction: though not present in mature sperm cells, MHC class II expression appears to be required during spe rmatogenesis to produce sperm cells capable of taking up foreign DNA, while CD4 molecules present on sperm cells mediate the nuclear interna lization of sperm-bound DNA. (C) 1997 Academic Press.