HUMORAL AND CELLULAR IMMUNE-RESPONSES IN CATTLE AND SHEEP INOCULATED WITH SARCOCYSTIS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 45  (8) , 1592-1596
Abstract
Cattle inoculated with S. bovicanis (= S. cruzi) and sheep inoculated with S. ovicanis were monitored for the appearance of Sarcocystis-specific antibodies antibodies and lymphocytes in the peripheral circulation. Anti-Sarcocystis antibody was identified by enzyme-linked immunosorbent assay [ELISA] whereas antigen-reactive lymphocytes were discerned by an in vitro lymphocyte blastogenic assay. The antigens used were the soluble fraction recovered from disrupted bradyzoites of mature sarcocysts. Cattle developed anti-Sarcocystis immunoglobulin (Ig)M responses, beginning 3-4 wk after inoculation, and IgG1 antibody responses, beginning 5-6 wk after inoculation. The increase in IgM antibody was relatively brief, returning to near preinfection levels in 2-3 mo. IgG1 antibody levels remained high for at least 5-6 mo. Neither IgG2 nor IgA antibody responses were demonstrable in cattle. In sheep, the IgG antibody levels followed a time course similar to that seen in cattle, except that the increase was slightly delayed (6-8 wk after inoculation was done). Measurable IgM antibody response was not seen in sheep. Cellular immunoresponsiveness as judged by in vitro lymphocyte blastogenesis in cattle was different from that in sheep. Sarcocystis-specific lymphocytes were demonstrable in the circulation of cattle within 15 days after they were inoculated, but the activity decreased rapidly. In sheep, reactive cells were not evident until 3-4 wk after inoculation were done, but peripheral blood lymphocytes taken from these sheep as long as 5-6 wk after the inoculations remained capable of mounting strong blastogenic responses. Neither the ELISA nor the blastogenic assay showed species specificity. Animals immunized with a given species of Sarcocystis gave similar in vitro responses to antigens from the immumnizing species and to other species of Sarcocystis. This apparent lack of specificity is probably due to the presence of crossreacting determinants in the crude antigen preparations used.