Cell surface antibodies in type 1 (insulin-dependent) diabetic patients. II. Presence of immunoglobulins M which bind to lymphocytes.

A standardized cell surface antibody assay was used to measure binding of circulating human immunoglobulins to rat or piglet splenocytes. In 100-fold diluted serum fractions, lymphocyte surface antibodies were detected in 30% of Type 1 (insulin-dependent) diabetic patients under 20 years of age but in none of 33 control subjects. Binding occurred with T and B lymphocytes, appeared unrelated to Fc receptors or protein glycosylation and was not attributable to insulin or albumin antibodies. At clinical onset of the disease, the lymphocyte surface antibodies belonged primarily to the IgM-class. Their presence was positively correlated to that of IgM-pituitary cell surface antibodies and their absorption by anterior pituitary cells occurred as well as by splenocytes. Lymphocyte surface antibodies remained present during the first years of insulin treatment. They were also detected in first degree relatives of lymphocyte surface antibody-positive patients. It is unlikely that IgM-lymphocyte surface antibodies mark the destructive process in the pancreatic B cell population. They may, instead, express a state of immune reactivity which precedes the formation of IgG-autoantibodies and therefore be associated with an event in the development of diseases such as Type 1 (insulin-dependent) diabetes.