Decay accelerating factor in guinea-pig reproductive organs

Decay accelerating factor (DAF, CD55) expressed in human reproductive organ s and gametes is thought to play a pivotal role in protection against autol ogous complement activation in the genital tract. To further investigate th e role of DAF in reproduction, we analysed DAF distribution in reproductive organs using guinea-pigs that express multiple DAF isoforms. In males, sig nificant staining was observed in testis on the elongated spermatids and sp ermatozoa. Levels of DAF mRNA with a shorter 3' untranslated region were si gnificantly 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 acrosoma l membrane as well as over their entire surface. Significant DAF expression was also observed on the epithelium of seminal vesicles from 4 weeks of ag e, with no increase thereafter in the mRNA. C3 mRNA was not detected in thi s tissue. In females, DAF was detected on the plasma membranes of oocytes t hrough follicle development and on the apical region of uterine epithelium, although the levels of DAF mRNA in these tissues were low. In addition, DA F was selectively expressed on the apical region of ciliated oviductal epit helial cells. The apical region of the ciliated cells comprising the effere nt ductule epithelium was also stained significantly, even at 12 days of ag e, while other epididymal epithelial cells were hardly stained at any age, suggesting that DAF is constitutively expressed on cilia.