The immunological consequences of antigen overload in experimental mycobacterial infections of mice.

Mice infected in the tail with M. ulcerans developed transient cell-mediated immunity which disappeared as the bacterial load increased. Lymph node cells from animals in this late phase of the disease transformed spontaneously in vitro. This transformation was inhibited by mycobacterial antigen. Lymph node cells from mice injected intravenously with 10(8) or 10(9) BCG also transformed spontaneously in vitro. Such animals did not become foot pad test-positive. Evidence is presented that the spontaneous transformation may represent an accumulation of specifically sensitized cells due to trapping in nodes overloaded with persistent antigen. The relevance of such a phenomenon to 'desensitization' in human and animal disease is discussed.