How causes connective tissue diseases? At the heart of the immune response is the ability to distinguish between self and non-self, or foreign Every body cell carries distinctive molecules that distinguish it as" self a Lymphocytes in patients with CTD lost the ability and cell-mediated immunity(involving T-cells), and humoral immunity(involving antibody-producing b- cells) are abnormally activatedHow causes connective tissue diseases?  At the heart of the immune response is the ability to distinguish between self and non-self, or foreign. Every body cell carries distinctive molecules that distinguish it as "self."  Lymphocytes in patients with CTD lost the ability and cell-mediated immunity (involving T-cells), and humoral immunity (involving antibody-producing B￾cells) are abnormally activated