Macrophage-dependent lymphocyte immunostimulation in cattle infected with Mycobacterium bovis and with Mycobacterium avium

The effect of T-2 toxin on the bovine immune system: cellular factors

The effect of T-2 toxin, a Fusarium metabolite, on the bovine cellular defense (immune) system was evaluated during high levels, chronic administration. The administration of T-2 toxin to calves at the rate of 0.6 mg/kg/day was associated with significant depression of lymphocyte responses to mitogens and significant decreases in chemotaxic migration of neutrophils.

In vitro assays of cell-mediated immunity in calves with persistent infections do not correlate with delayed skin hypersensitivity

A long-term kinetic study of the immune response of four calves experimentally infected with a M. avium strain was made using the following tests: lymphocyte stimulation (LS), leukocyte migrationinhibition (LMI), delayed skin hypersensitivity (DHS), and a radioimmunoassay (RIA) procedure for antibodies to M. avium. The cell-mediated immune (CMI) responses measured by these tests showed different courses during the infection period. The LS test showed several periods of peak values and the LMI test two peaks of responses of relatively shorter duration. At the end of the experimental period the DHS responses had decreased to insignificant levels, whereas the lymphocytes from all the calves responded in the LS test. No correlation could be detected between CMI and antibody mediated responses, and only two of the infected calves showed clear cut antibody responses measured by RIA. The results probably reflect the measurement of different aspects of the CMI response in the different test systems. The cyclical nature of the CMI measured by the LS and LMI tests may indicate the influence of regulatory mechanisms by suppressing lymphocyte sub-populations.