Cell Differentiation, 11 (1982) 303--304 303 Elsevier/North-Holland Scientific Publishers, Ltd. THE HETEROGENEITY OF THE SPERM SURFACE AS ANALYZED WITH MONOCLONAL ANTIBODIES E.M. EDDY, J.C. HERR, F.A. FEUCHTER, R.B. VERNON, C.H. MULLER and B.A. FENDERSON Department of Biological Structure, University of Washington School of Medicine, Seattle, WA 98195, U.S.A. mouse sperm monoclonal antibodies mosaic surface Cell surface components of spermatozoa are probably involved in events of cell recog- nition, interaction and attachment, processes central to fertilization and early develop- ment. However, which surface components are involved and how they are involved are unknown. Monoclonal antibodies (MAb) are being used to identify and characterize cell surface components of germ cells and to study their roles in cell surface events in the life history of the germ cell line. Previous studies have demonstrated that the sperm surface is a mosaic of restricted do- mains. A variety of different antisera to sperm have been shown to recognize nonrandomly distributed antigens (Koehler, 1978). In add- ition, lectin binding sites, surface charge, in- tramembranous particles (Koehler, 1978)and attachment sites for covalent surface labels (Gabel et al., 1979) are heterogeneously dis- tributed. However, MAb provide a more spe- cific means for analysis of the location of individual moieties than these other methods. The present studies were carried out in mice because they respond well to syngeneic immunization with the cells being used, mouse myeloma cell lines are available for fusion with splenocytes from immunized mice, and the genetics and immunology of this species are well characterized. Immunization, hybrid- ization and clonal screening procedures were performed as previously described (Feuchter et al., 1981), and panels of monoclonal anti- bodies against sperm, testicular, and terato- carcinoma cells were used to examine the distribution of individual components on the sperm surface. Four panels of MAb have been produced and have been partially characterized for re- activity against sperm, spermatogenic cells, teratocarcinoma cells, tumor cells and somatic tissue cells. Of the 26 MAb studied in this way so far, 13 recognize surface antigens with restricted distribution on mouse epididymal spermatozoa (Table I). The MAb produced show five distinct bind- ing patterns on mouse sperm: the whole head, the anterior acrosome, the posterior acrosome, the posterior part of the head caudal to the acrosome and the tail. The MAb so far pro- duced by immunization with spermatozoa from the epididymis do not bind to the sur- face of sperm from the testis, indicating that the antigens recognized are appearing as a result of changes at the sperm surface in the epididymis (Feuchter et al., 1981). These antigens might originate by insertion into the surface from the sperm cytoplasm, by ex- posure or modification of existing components on the sperm surface or by attachment to the surface of externally produced components. It has been found that in one case, the antigen which appears on the surface of the taft, the component is secreted by the epithelium in a restricted region of the epididymis (Vernon et al., 1982). The MAb produced by immunization with testicular cells or teratocarcinoma cells show 0045-6039/82/0000--0000]$02.75 © 1982 Elsevier/North-Holland Scientific Publishers, Ltd.