Suppressor activity of bovine Fc gamma positive cells during a persistent infection with Mycobacterium avium.

The cell mediated immune response (CMI) was measured in calves after experimental infection with Mycobacterium avium. Using the tuberculin skin test a CMI response could be measured from four to 14 weeks after infection, and with a lymphocyte stimulation (LS) test from six to 40 weeks. One year after infection no CMI response was detected by either of the tests, in spite of the fact that in such calves M avium bacteria could be found in the intestinal lymph nodes at autopsy. After removal of mononuclear cells bearing receptors for the Fc part of IgG, the peripheral blood lymphocytes obtained from a calf infected one year earlier responded to M avium pure protein derivative in the LS test in contrast to lymphocytes obtained from uninfected calves.