IgA bovine serum albumin antibodies are increased in newly diagnosed patients with insulin-dependent diabetes mellitus, but the increase is not an independent risk factor for diabetes.

We studied the significance of antibodies to bovine serum albumin (BSA) as a risk factor for insulin-dependent diabetes mellitus (IDDM) in a case-control setting. IgA and IgG antibodies to BSA and ovalbumin were measured from sera of 104 patients with newly diagnosed IDDM and of 111 matched controls by enzyme-linked immunosorbent assay. Patients with diabetes had significantly higher levels of IgA antibodies to BSA (p = 0.003); IgG antibodies also tended to be higher (p = 0.08). Levels of IgA antibodies to ovalbumin were similar in the patients and controls, but IgG antibodies were higher in controls (p = 0.02). When antibodies to BSA, beta-lactoglobulin, whole cow's milk and islet cell antibodies were studied as risk determinants of IDDM in a multivariate, logistic regression analysis, IgA antibodies to beta-lactoglobulin and to cow's milk were independently associated with the risk (p = 0.037 and 0.048, respectively), while antibodies to BSA were not a significant risk factor. The results question the role of BSA as a cross-reacting antigen with pancreatic beta-cell surface proteins in the aetiology of IDDM.