Bovine venereal vibriosis: variations in immunoglobulin class of antibodies in genital secretions and serum.

The immunoglobulin classes of antibodies to Campylobacter (Vibrio) fetus in cervicovaginal mucus (CVM) were determined by the indirect fluorescent antibody test at sequential periods, since the order of class appearance has not been established for specific secretory immune responses. In the local immune response to C. fetus immunoglobulin M (IgM) antibodies appeared first, immunoglobulin A (IgA) antibodies next, and immunoglobulin G (IgG) last. IgM antibodies were quite transient, but IgG antibodies remained longer, and those of the IgA class persisted until the end of the experimental period (up to 10 months). Since differences appear to exist between immune mechanisms at cervicovaginal and uterine sites, as well as between immune responses induced by local and systemic immunizations, the immunoglobulin classes of antibodies in uterine secretions were compared with the classes in CVM and serum. Uterine antibodies arose coincidently with uterine lesions in heifers slaughtered after short periods of infection. In convalescent animals only IgA antibodies were found in CVM, whereas the predominant class of antibodies in the uterine secretions was IgG(1) in three of four animals studied. Only IgG antibodies were detected in CVM and uterine secretions of systemically immunized animals. These findings could account for faster clearance of C. fetus from the uterus than from the cervicovaginal area in locally infected animals and for failure of colonization in systemically immunized animals, because IgG antibodies are good opsonins and IgA antibodies are not. IgA antibodies do immobilize C. fetus, however, so they could prevent recolonization of the uterus in cervicovaginal carriers.