Immunological reactivity to a mycobacterial fraction is associated with nonspecific suppression of immunological responsiveness in vivo.

Previously reported studies revealed that spleen cells from BALB/c mice immunized against a methanol extraction residue (MER) fraction of tubercle bacilli are defective in the in vitro generation of antibodies to SRBC and in allogeneic responsiveness against C57BL spleen cells. We now show that mice repeatedly immunized with MER also exhibit a depressed capacity to respond to antigenic stimulation in vivo. Thus mice repeatedly injected with MER were impaired in their ability to react to antigenic stimulation by SRBC and by C57BL spleen cells. Impairment in the response to SRBC immunization was expressed at the level of delayed-type hypersensitivity (DTH) as well as of antibody production. The response of MER hyperimmunized mice to contact sensitization with dinitrofluorobenzene (DNFB) was not impaired, but the lymph node cells of DNFB-sensitized animals had a depressed ability to respond to in vitro stimulation by the monovalent hapten dinitrobenzene sulfonate (DNBS). The present findings indicate that extensive exposure to an immunogenic immunomodulating mycobacterial fraction can lead to a depressed responsiveness to unrelated antigenic stimulation.