Furthermore, the increase of extrathymic HLA-DR+ DP cell population in patients having the cardiac form of human Chagas disease was also correlated with the augmentation of the frequencies of activated HLA-DR+ single-positive CD4+ T cell (Fig. 7c) and CD8+ T cell subsets (Fig. 7d) obtained from chronically infected chagasic patients. Here, CD4 is linked to Chagas disease.