Complement-Dependent Antibody Mediated Cytotoxicity (C' AMC) in Patients with Newly Diagnosed Insulin-Dependent Diabetes Mellitus

Summary

Serum activities of complement-dependent antibody mediated cytotoxicity (C' AMC) were determined in 36 consecutive patients with newly diagnosed insulin-dependent diabetes mellitus (IDDM). The sequential exposure of 51Cr labeled neonatal rat islet cells to patient serum and rabbit complement revealed the presence of C' AMC in 28 IDDM subjects. The C' AMC titres ranged between 1:4 and 1:512 and were not related to the C' AMC activity of a given sample as measured at a standard dilution (1:4). — In comparison to the clinical characteristics of 21 IDDM patients with negative C' AMC, higher C' AMC titres (≥1:32) were associated with a lower nican age at diagnosis of IDDM (12.2 ± 2.1 vs. 19.0 ± 2.3 years; p < 0.05), with a higher frequency of infections up to 6 months prior to diagnosis (6 out of 11 vs. 3 out of 21 patients; p < 0.05) and, although statistically not significant, a preponderance of female sex together with a decreased frequency of HLA-DR4. In contrast, fasting C-peptides levels, HLA-DR3 antigen frequency and Coxsackie B_1–6 virus antibody titres were not related to the C'AMC titres. — It is concluded that (1) C'AMC titration is superior to the detection of initial C' AMC levels for evaluating the strength of the complement-dependent humoral immune response towards islet cell surface (auto)antigen(s), and (2) infectious agents may be involved in eliciting a C' AMC response.

Key words

Insulin-dependent diabetes mellitus - Titres of complement-dependent antibody mediated cytotoxicit - ⁵¹Cr release - C-peptide levels