Sites of protein absorption and secretion in the epididymis and changes in sperm antigenicity during their maturation and senescence were investigated. Tissue and sperm samples from normal bulls, unilaterally vasoligated bulls and bulls in which one epididymis was ligated distal to the caput epididymidis were examined using fluoresceinconjugated immune globulins. The globulins were obtained from antisera against spermatozoa from bull cauda epididymidis, ejaculated spermatozoa, plasma from the cauda epididymidis and seminal plasma. In mature spermatids, acrosomal immunofluorescence was homogeneous. After spermatozoa had traversed the first half of the caput epididymidis, the apical body was especially prominent. Specific immunofluorescence of the post-nuclear cap, cytoplasmic droplet, midpiece, and principal piece was not observed except in presumably senescent spermatozoa from spermatocoeles.
Non-ciliated, antigen-secreting cells were detected by their immunofluorescence in the epithelium of the efferent ducts within the proximal caput epididymidis. These secretory cells produce sperm-coating proteins which are antigenically similar to certain components of seminal vesicle fluid. Immunofluorescence of the apical cytoplasm and stereocilia in the proximal caput epididymidis indicated that this epithelium probably absorbed sperm-specific proteins emanating from the testis.
Immunofluorescence in the apical cytoplasm of the epithelium lining the corpus and proximal cauda epididymidis was suggestive of secretory activity. Similar fluorescence in the epithelium of the vas deferens may have resulted from the absorption of proteins.