Cell-mediated immunity in the aetiopathogenesis of insulin-dependent (type I) diabetes mellitus.

We have investigated lymphocyte subpopulation levels with monoclonal antibodies in newly diagnosed insulin-dependent (type I) diabetics and in unaffected siblings of type I diabetic probands with islet cell antibodies. Our data show that in newly diagnosed diabetics there is 1) a decrease in T cells with suppressor phenotype, 2) an increase of T cells with cytotoxic phenotype and 3) the presence of "activated" T cells. The latter have also been found in some unaffected siblings with islet cell antibodies. These results suggest that cellular immune alterations are present, not only at diagnosis, but also in normal but "susceptible" individuals. "Activated" T cells could be a "disease" marker, but their better definition in terms of specificity should be established.