Experimental myocarditis: in vitro and in vivo studies of lymphocytes sensitized to heart extracts and group A streptococci.

Cytotoxicity was found in 78 per cent of rat heart cell cultures in contact with lymphocytes sensitized to rabbit heart extracts and in 65 per cent of those exposed to lymphocytes sensitized to rat heart. Lymphocytes sensitized to group A streptococci were cytotoxic on 82 per cent of the cultures while controls were affected in less than 20 per cent and to a much more limited extent. Agglutination of the sensitized lymphocytes by antilymphocytic serum inhibited the cytotoxic effect. Passive transfer of lymphocytes from Lewis rats sensitized to rabbit heart produced myocarditis in thirteen of fourteen rats. The significance of these findings is discussed in relation to the pathogenesis of experimental myocarditis.