Soluble immune complexes in the sera of newly diagnosed insulin-dependent diabetics and in treated diabetics.

Soluble immune complexes were detected by the Raji cell assay in seven out of thirteen newly diagnosed insulin-dependent diabetics, six of whom had islet cell antibodies (ICAb) in the serum. None of the others had ICAb. The titres for a wide range of viral antibodies were similar in these thirteen diabetics as in age- and sex-matched controls, except for antibodies to Coxsackie B4. Six had titres of Coxsackie B4 antibodies greater than or equal to 1:32, but only three of these had evidence of immune complexes in the serum, and these were not correlated with the titres of Coxsackie B4 antibodies. None of these diabetics had antibodies to insulin and none of their age- and sex-matched controls had evidence of immune complexes in the serum. 53% of thirty-two diabetics treated with insulin and 10% of fifty-two diabetics requiring oral hypoglycaemic agents (OHA) or diet had evidence of immune complexes in the serum, compared to 6% of control subjects. High titres of insulin antibodies correlated with evidence for immune complexes. There was a stronger tendency for immune complexes to occur in the presence of moderate titres of insulin antibodies when the age at onset of insulin-dependent diabetes was less than 30 years. Out of sixteen patients treated with heterologous insulin for 13 years or more, and who also had late diabetic complications, twelve had immune complexes in the serum.