Fig. 6.

Predominance of Kappa light chains in anti-IA-2 autoantibodies suggest clonal restriction of autoreactive B cells. A. Assessment of clonality in anti-IA-2 autoantibodies was achieved by determination of the Kappa/Lambda light chain ratio in immobilised total IgG (Total IgG) verses anti-MPB-IA-2 fusion protein specific IgG (Anti-IA-2 Abs) from a patient (T1D069) positive for anti-IA-2 autoantibodies. While the Kappa/Lambda ratio of approximately 1:1 in total IgG suggests near equal light chain representation in total serum IgG, for antibodies recognising IA-2 epitopes present in the MBP-IA-2 fusion protein, a ratio of approximately 2:1 indicates predominantly Kappa chains, indicative of clonal restriction in anti-IA-2 autoreactive B plasma cells. B. A predominance of Kappa chains in anti-IA-2 autoantibodies (Kappa/Lambda ratio 1.44:1) relative to total IgG (Kappa/Lambda ratio 1:1) in a second patient (T1D019) positive by MPB-IA-2 fusion protein ELISA confirms clonal restriction of anti-IA-2 autoreactive B plasma cells. C. In contrast to patients with T1D, the Kappa/Lambda ratio of IgG from a healthy control (CTR068) did not display evidence of increased Kappa expression in antibodies immobilised by fusion protein ELISA. The Kappa/Lambda ratio of 1.36:1 was observed in total IgG from this individual, with a post MBP-IA-2 ELISA (NS IgG) ratio of 1.03:1. Data represents normalised means and SEM from at least n = 6 individual replicates from 2 separate experiments.