Impaired immune function during the periparturient period contributes to the increased susceptibility of the cow to infectious disease around the time of calving. Changes in subpopulations of peripheral blood mononuclear cells during the immediate periparturient period can contribute to the observed immunosuppression in cows, but it is not known exactly when and what changes occur. Using a flow cytometer and monoclonal antibodies directed against antigenic markers on mononuclear cells, the populations of CD3, CD4, CD8, and gamma delta T-cell receptor positive cells were examined in eight periparturient Jersey cows during the 2 wk before and 2 wk after parturition. The percentage of cells that were positive for CD3, CD4, and gamma delta T-cell receptor markers exhibited a significant decline before calving and reached a nadir at calving. These percentages did not return to precalving levels until 2 wk after calving. These data are compatible with the hypothesis that declining T-cell populations may contribute to the immunosuppression reported for dairy cows at calving.

No abstract

Growth and sexual maturity were compared among Monterey Botryllus schlosseri colonies cultured in the laboratory and in Monterey Marina in two separate studies: Phase I April to July 1984, a time when Botryllus growth is rapid in the field, and Phase II December 1984 to March 1985, a time when growth is minimal in the field. Laboratory colonies were kept in tanks of standing, aerated filtered seawater at 15C, 20C, and 24C; the seawater was changed daily or on alternate days. Food types were two concentrations of an algal mixture and five concentrations of Liquifry, a commercially available food for filter-feeding marine invertebrates. All algae-fed colonies did poorly. During Phase I, the colonies kept in Monterey Marina grew much faster than those in the laboratory, but they took longer to reach sexual maturity than the Liquifry-fed colonies grown at 20C and had a lower survivorship. In Phase II, Botryllus growth rates and survivorships in seven of the eight laboratory treatments were better than those of marina colonies. These laboratory treatments yielded a substantial proportion of sexually mature colonies, whereas none of the marina colonies produced eggs during Phase II.

The importance of CD4+ cells and gamma interferon (IFN-y) in the resolution ofestablished Cryptosporidium parvum infection was investigated with a murine model of cryptosporidiosis in severe combined immunodeficient (SCID) mice. C. parvum-infected SCID mice were reconstituted with spleen cells from immunocompetent donors. The recipients were able to resolve their C. paryum infection by 17 days postreconstitution. Treatment of reconstituted SCID mice with either anti-CD4 monoclonal antibodies to deplete them of CD4+ cells or with anti-IFN-y to neutralize IFN-y activity reduced or eliminated their ability to resolve C. parvum infection, whereas treatment with either anti-CD8 monoclonal antibodies or anti-asialo-GM1 antibodies had no effect. We also found C. parvum-specific antibodies in serum samples from two of four reconstituted SCID mice killed on postreconstitution day 17 but not in unreconstituted SCID mice. Moreover, anti-CD4-treated mice had no detectable specific antibodies to C. parvum, whereas all mice treated with either anti-CD8 or anti-asialo-GM1 had substantial levels of specific antibodies in their serum. Although the role of the specific antibody is not known, these findings clearly indicate that resolution of an established C. parvum infection in immunologically reconstituted SCID mice is dependent on both CD4+ cells and IFN-y. Cryptosporidium parvum has emerged as an important cause of intestinal infections in immunocompromised humans, especially in AIDS patients, whereas the infection is usually self-limiting in immunocompetent hosts (13, 21). The