**6. Complement function**

In a study of 86 DM type 1 patients, 22 (26%) had a serum complement factor 4 concentration (C4) below the normal range [10]. The low C4 values did not appear to be the result of consumption. Since non-diabetic identical twins also had a C4 concentration below normal, and the genes encoding C4 are linked with the antigens DR3 and DR4 (which are expressed in 95% of the Caucasian diabetic patients in contrast to 40% of the general population [6]), the authors suggest that the reduced C4 level may be an inherited phenomenon [10].
