The role of macromolecular components in anti-gamma, alpha, mu, kappa, lambda, C3 and C4 antiglobulin sera

Summary . Studies are described of the early and late responses of rabbits immunized with human IgG protein. Early macroglobulins (19S) antiglobulin antibody is compared with 7S antibody in tests against red cells strongly and weakly coated by IgG anti-Rh(D) antibody. The 19S antibody, when reacted on a glass plate, is slower to produce maximum agglutination than 7S antibody, is enhanced by 4% human serum albumin, and is of at least equal sensitivity in detecting very weakly sensitized erythrocytes. The 19S antibody shows no loss of potency during 1 yr storage at - 20°C, but is unstable beyond 6 mth storage at 4°C. The 19S antibody is non-precipitating against its specific antigen, which complicates assessment of its specificity. It is shown that admixture of 19S with 7S antiglobulins alters the manifestation of the prozone characteristic of the 7S antibody alone. Macroglobulin antiglobulin reagents raised against human γ, α, μ, K, λ, C₃ and C₄ antigens are compared with 7S reagents of similar specificities in tests against coated cells from 14 patients with acquired autoimmune haemolytic anaemia (AAHA), three patients receiving methyldopa, and against normal cells sensitized with anti-D, anti-Fy^a, anti-Kell, anti-Le^a and anti-Jk^a isoantibodies. The results put macroglobulin antiglobulin reagents in perspective in relation to the broad field of antiglobulin testing.