Lymphocyte abnormalities in the BB rat.

The BB rat has a marked T cell lymphocytopenia, with a near absence of peripheral "helper" T cells recognized by monoclonal antibody W3/25 (W3/25+ T cells). The lymphocytes of the BB rat's spleen and thymus were examined for the presence of W3/25+ T cells, which were found to be absent in the spleen but present in normal amounts in the thymus. Concanavalin A (Con A) responsiveness was absent in the BB's peripheral blood and spleen but present in the thymus. Thus, in these three lymphoid compartments, Con A responsiveness directly correlated with the presence or absence of W3/25+ T cells. These lymphocyte abnormalities in the BB rat are notably different from lymphocyte changes present in human type I diabetes.