Immune recognition in the streptococcal carditis of mice: the role of macrophages in the generation of heart-reactive lymphocytes.

The role of immune T cells and of streptococcus-pulsed M phi in the production of cardiac lesions, as well as the ability of M phi to present streptococcal antigens to mouse lymphocytes, was investigated. Cells of mice infected with extracts of group A streptococcus were able to induce the appearance of heart lesions when transferred to syngeneic receptors as well as to transfer DTH reactions to syngeneic heart extracts. Streptococcus-pulsed M phi were also able to induce heart lesions and an increase in the serum CPK activity when injected into syngeneic receptors. This last phenomenon was only observed in mice aged 5 mo or more. Furthermore, it was shown in an in vitro model of T cell proliferation that peritoneal M phi pulsed with group A streptococci are able to induce a specific response to syngeneic cardiac extracts. M phi pulsed with group G streptococcus failed to induce such a response. Those findings are discussed as part of a model for the induction of rheumatic cardiac lesions in which M phi display a central role by selecting antigenic determinants from the pathogenic organism for presentation to immunocompetent cells.