LYMPHOCYTE-REACTIVITY TO OSTERTAGIA-OSTERTAGI L3-ANTIGEN IN TYPE-I OSTERTAGIASIS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 45  (2) , 230-233
Abstract
To better understand the immune response of calves infected with O. ostertagi, studies were conducted to examine cell-mediated immune responses to L3 antigen and phytohemagglutinin (PHA) by lymphocyte reactivity assay. The L3 antigen was prepared by freeze-thawing and sonication of exsheathed O. ostertagi L3. Antigen preparations contained 40-60 .mu.g of protein/ml and no detectable endotoxin. Cell-mediated immune responses of peripheral blood lymphocytes were determined in 3 groups of 12 calves each: calves given consecutive multiple dose inoculations with L3; calves naturally infected by pasture exposure to L3; and noninfected controls. Consecutive multiple-dose-inoculated calves showed marked increases in stimulation indices (SI) to L3 antigen over the SI of naturally inoculated calves (56.5 and 25.8, respectively). Negative SI were obtained in calves of the noninoculated control group (-1.0). No significant difference (P .gtoreq. 0.05) in response to PHA was obtained between lymphocytes from calves inoculated with O. ostertagi and lymphocytes obtained from noninoculated control calves. There was significant (P .ltoreq. 0.01) agreement between positive SI and evidence of patent infection (development of type I ostertagiasis). Specificity of lymphocyte reactivity was determined, using lymphocytes from 4 O. ostertagi- and 2 Cooperia punctata-infected calves after challenge inoculation. Positive SI to L3 antigen were obtained, using lymphocytes from either O. ostertagi- or C. punctata-infected calves, indicating that there may be a lack of genus specificity for O. ostertagi L3 antigen in lymphocyte reactivity assay. Kinetic studies of lymphocyte reactivity to L3 antigen and PHA showed that responses were briefly suppresed to both of these stimuli in prepatent calves. Apparently transient nonspecific suppression of cell-mediated immune responses occurs during prepatent periods of type I ostertagiasis. This immunosuppression phenomenon may have a role in the pathogenesis of O. ostertagi and in development of immunity to ostertagiasis.