IMPORTANCE OF THE INTEGRITY OF THE INTER-HEAVY-CHAIN DISULFIDE BOND OF RABBIT IGG IN THE ACTIVATION OF THE ALTERNATIVE PATHWAY OF HUMAN-COMPLEMENT BY THE F(AB')2 REGION OF RABBIT IGG ANTIBODY IN IMMUNE AGGREGATES

  • 1 January 1981
    • journal article
    • research article
    • Vol. 42  (1) , 75-82
Abstract
Immune aggregates formed from either rabbit IgG antibody or F(ab'')2 antibody, and antigen, caused the same extent of utilization of alternative pathway [AP] components when incubated with human serum under conditions allowing only alternative pathway activation. The F(ab'')2 region of the antibody molecule can cause AP activation and this activation is not affected by the presence of the Fc region of the molecule when only alternative pathway activation is permitted. Under conditions allowing activation of both the classical and AP, increased AP activation was obtained with IgG antibody aggregates compared to that obtained with F(ab'')2 antibody aggregates. On reduction and alkylation of principally the inter-H chain disulfide bond in the IgG antibody, prior to aggregate formation, no APactivation by IgG aggregates took place under conditions allowing only AP activation. Treatment of the IgG antibody with reducing agent alone, or alkylating reagent alone, followed by dialysis and aggregate formation, yielded aggregates which caused AP activation values close to those obtained for untreated IgG aggregates. Apparently the integrity of the inter-H chain disulfide bond of rabbit IgG antibody in immune aggregates is necessary to allow the F(ab'')2 region of the IgG molecule to activate the human complement the AP.