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Localization of histocompatibility and organ specific antigens on mouse spermatozoa.

Further studies on the topographic localization of histocompatibility and organ-specific antigens on mouse spermatozoa have been reported. Specific antisera to a histocompatibility antigen (H-2a) and a serum prepared by injecting male mice with syngeneic testicular homogenate were labeled with peroxidase and the antigens were located by immunoelectron microscopy. The organ-specific antigen was located on the sperm head and occasionally on the midpiece, whereas the H-2 antigen was confined to the sperm head. The observations were not quantitative, because of the obvious limitations in the examination of thin sections. The distribution of the 2 antigens may be related to the functions of the various parts of the spermatozoa, although no clear correlation could be suggested. The authors indicate several points of discussion arising from their observations. There is no general agreement at present about the presence or absence of histocompatability antigens on spermatozoa. The reported location of these antigens on spermatozoa conflicts with some earlier results. The present observations must also be considered in relation to the fluid mosaic model of cell membranes, for the localization of antigens to particular sites imples that restrictions are placed on the movement of some membrane constituents.