Desensitization: effects on cutaneous and peritoneal manifestations of delayed hypersensitivity in relation to...

Guinea pigs exhibiting delayed hypersensitivity may be desensitized by a single large dose of antigen administered intramuscularly. In the present experiments, desensitization with a soluble protein such as egg albumin (EA) or bovine gamma-globulin (BGG) was nonspecific in that they suppressed both cutaneous reactivity and the macrophage disappearance reaction (MDR) to unrelated antigen in doubly immunized animals. In contrast, myobacterial antigen, at the dose studied, showed limited specificity in that it could suppress the MDR but not a skin test to an unrelated antigen. Induction of an MDR was shown to be associated with the appearance of macrophage migration inhibitory factor (MIF) and chemotactic activity in the peritoneal exudate fluid. Pretreatment with desensitizing doses of mycobacteria prevented the EA-induced appearance of MIF in the peritoneal fluids. In contrast, chemotactic activity could still be recovered, even though the MDR was suppressed. Mycobacteria functioned as a specific desensitizer not only with respect to cutaneous reactivity, as stated above, but also with respect to the production of chemotatic factor by peritoneal exudate cells. In contrast, mycobacteria functioned as a nonspecific desensitizer with respect to both the MDR and MIF production. These results suggest that the MDR may be an in vivo manifestation of MIF activity, whereas the cutaneous delayed hypersensitivity reaction may be more dependent upon chemotactic activity. These observations reported here, taken in conjunction with previously described in vitro studies, suggest that desensitization is a complex phenomenon which may be the result of several different mechanisms acting separately or in concert. The apparent discrepancies in the literature as to whether or not desensitization is a specific process would appear to arise from differences in the experimental model and the particular antigen used.