ENHANCED MYOCARDIAL LESIONS IN CHRONICALLY TRYPANOSOMA-CRUZI-INFECTEDRATS SUBJECTED TO ADULT THYMECTOMY

Control animals and rats infected 90 days earlier, by inoculation of 1 x 10(6) trypomastigotes of Trypanosoma cruzi at weaning, were subject ed to adult thymectomy (ATx) or sham operation (S-ATx) and assessed 3 months later for the presence of myocardial lesions and levels of lymp h node and spleen T-cell populations. Chronic focal myocarditis (CFM) developed in 78% and 84% of S-ATx or ATx infected rats, respectively. While the two groups of infected rats did not differ as to the occurre nce of myocardial lesions, large foci of CFM were more prevalent in AT x infected rats. Chronic T. cruzi (Tc) infection resulted in decreased CD4+ and increased CD8+ lymph node and spleen cell, with CD8+ lymphoc ytes being lowered to normal values in the spleen of the ATx infected group. It is suggested that ATx might act by interfering with a down-r egulating immunoregulatory mechanism, leading to an exacerbation of au toimmune reactions believed to be involved in the generation of myocar dial damage.