Decay accelerating factor in guinea-pig reproductive organs.

Decay accelerating factor (DAF, CD55) expressed in human reproductive organs and gametes is thought to play a pivotal role in protection against autologous complement activation in the genital tract. To further investigate the role of DAF in reproduction, we analysed DAF distribution in reproductive organs using guinea-pigs that express multiple DAF isoforms. In males, significant staining was observed in testis on the elongated spermatids and spermatozoa. Levels of DAF mRNA with a shorter 3' untranslated region were significantly enhanced in testis from 9 weeks of age, indicating the presence of DAF mRNA and protein synthesis of spermatozoa DAF in late haploid germ cells. Epididymal spermatozoa appeared to express DAF on the inner acrosomal membrane as well as over their entire surface. Significant DAF expression was also observed on the epithelium of seminal vesicles from 4 weeks of age, with no increase thereafter in the mRNA. C3 mRNA was not detected in this tissue. In females, DAF was detected on the plasma membranes of oocytes through follicle development and on the apical region of uterine epithelium, although the levels of DAF mRNA in these tissues were low. In addition, DAF was selectively expressed on the apical region of ciliated oviductal epithelial cells. The apical region of the ciliated cells comprising the efferent ductule epithelium was also stained significantly, even at 12 days of age, while other epididymal epithelial cells were hardly stained at any age, suggesting that DAF is constitutively expressed on cilia.