Raised IgG and IgM in "epidemic" IDDM suggest that infections are responsible for the seasonality of type I diabetes.

Serum levels of immunoglobulins G, A and M were quantitatively measured at diagnosis and at regular intervals for four years in 92 type I (insulin-dependent) diabetes patients. The patients were 0.8-15.99 years of age at diagnosis. Thirty-six of them got diabetes during periods of high incidence (the "epidemic" group) and 56 of them were diagnosed during periods of seemingly low incidence (the non-"epidemic" patients). Fifty percent (18/36) of the "epidemic" group had infections less than two months preceding diagnosis as compared to 29% (16/56) (p less than 0.01) of the non-"epidemic" patients. At diagnosis immunoglobulins G, and M in the "epidemic" group were 11.28 +/- 2.0 and 1.97 +/- 0.77 as compared to 9.9 +/- 2.3 (p less than 0.01) and 1.31 +/- 0.58 (p less than 0.001) respectively in the non-"epidemic" patients. The same highly significant differences were observed when mean values of IgG and IgM were compared between children who had infections less than two months before diagnosis and those without preceding infections. Except for slightly higher (p less than 0.12) total (OKT3) T-lymphocytes and higher (p less than 0.03) B-lymphocytes at diagnosis in the "epidemic" group, there were no significant differences in quantitative T- and B-lymphocyte subpopulations between various groups. 6.3% (2/32) of the patients who had preceding infections had HLA-DR3/non-DR4 genotypes as compared to 30.6% (15/49); p less than 0.001, of those patients without preceding infections.(ABSTRACT TRUNCATED AT 250 WORDS)