Characteristics of blood cells responding to insulin in children with insulin-dependent diabetes

Cellular immunity to human insulin in individuals at high risk for the development of type I diabetes mellitus

In order to investigate the role of insulin as a potential target autoantigen of cellular immunity in the prediabetic period, proliferative responses of T lymphocytes to human insulin were studied in nine islet-cell antibody (ICA) + first-degree relatives of patients with Type I diabetes (individuals at high risk for the development of Type I diabetes, or the 'prediabetic' group, which was never treated with insulin) and in 12 control individuals. Insulin autoantibodies were present in 6/9 (67%) of the prediabetic subjects and none of the controls. Peripheral blood lymphocytes were collected on Ficoll and incubated with human insulin, control antigens, or media alone for 5-6-day and 9-10-day incubation periods. Cells were pulsed with 3H-thymidine, harvested, and analysed in a scintillation counter. Results are expressed as stimulation index (SI = cpm with antigen/cpm without antigen), with a SI greater than or equal to 1.5 considered a positive response. Eight of nine (89%) prediabetic individuals responded positively to insulin after a 9-10-day incubation period, in contrast to four of 12 (33%) control subjects, P less than 0.05. The mean proliferative response to insulin after 9-10 days' incubation was 2.1 +/- 0.4 and 1.2 +/- 0.1, for the prediabetic and control groups, respectively. The proliferative response to insulin was not directly correlated with levels of insulin autoantibodies (r = -0.05, NS). These data suggest that most individuals at high risk for the development of Type I diabetes display a cellular immune response to insulin, and a subset of these individuals does not display a concomitant humoral immune response to insulin based on the presence or absence of insulin autoantibodies.

Immune responses to insulin and lymphocyte subclasses at diagnosis of insulin-dependent diabetes and one year later

Insulin induced proliferation of blood mononuclear cells, numbers of blood B and T cells, of blood lymphocytes bearing interleukin 2 receptors or HLA class II molecules were assayed at diagnosis and one year later in children with insulin-dependent diabetes mellitus (IDDM) and in healthy children. Insulin and islet cell antibodies were also studied. The numbers of lymphocytes expressing HLA class II molecules and NK cells were increased at diagnosis. T cells of the helper/inducer (CD4+) phenotype and interleukin 2 receptor positive lymphocytes were increased both at diagnosis and one year later. At diagnosis, insulin induced proliferation of blood mononuclear cells in 65% and one year later in 50% of the patients. Insulin antibodies were detected in 10% and islet cell antibodies in 90% of patients at diagnosis, and in 67% and 78%, respectively, one year later.

Immune responses to insulin in patients with insulin-dependent diabetes mellitus

To examine the effect of the major histocompatibility locus (HLA) and the duration of insulin-dependent diabetes (IDDM) on immune responses to insulin we assayed insulin induced proliferation of blood mononuclear cells and measured insulin antibodies in 66 patients with newly diagnosed and in 56 patients with longstanding IDDM matched for the age at onset (less than or equal to 15 years). In up to two thirds of the patients blood mononuclear cells responded to insulins by proliferation, and insulin antibodies were found in two thirds of patients with IDDM of long duration. Insulin proliferation or antibodies were not associated to any particular HLA antigen. The frequency of HLA-DR3 in patients with newly diagnosed IDDM was not increased unlike in patients with IDDM of long duration. In addition, HLA-B8 was associated to HLA-DR3 nearly twice as often in patients with newly diagnosed IDDM as in patients with longstanding IDDM. Thus, patients with IDDM of recent onset and diagnosed within the last three years more frequently responded to insulin by proliferation and less often had HLA-DR3 than patients with IDDM of long duration and diagnosed about 20-25 years earlier.