Active components of antiglobulin sera reacting with red cells sensitized with natural and immune anti-A haemagglutinins.

Abstract

Four antihuman globulin sera (AHG) were prepared by immunizing rabbits with (1) purified gamma globulin and (2) anti-A haemagglutinins purified by elution from sensitized cells namely, (a) natural anti-A from a male who had received no known antigenic stimulus, (b) immune anti-A + B after delivery, and (c) immune anti-A from the cord blood of an infant with mild ABO haemolytic disease. The highest dilution of AHG sera agglutinating haemagglutinin-sensitized cells was essentially the same with the natural (2a) and immune (2b) sera with titers from 1:40 to 1:320 while with the immune (2c) serum the titers ranged from 0 to 1:20. The antihuman gamma globulin (AHGG) serum did not agglutinate cells sensitized with the natural anti-A and showed a titer of 1:2560 with cells sensitized with immune anti-A+B.Micro-Kjeldahl analysis of the four AHG sera precipitated with gamma globulin showed marked differences in μg nitrogen per ml of gamma globulin and of antigamma globulin and in the ratio of antibody to antigen at maximum precipitation. There appeared to be a quantitative relationship between the activity of serum in the antiglobulin test and the ability of serum to combine specifically with gamma globulin. Quantitative analysis snowed that the amount of gamma globulin in μg nitrogen required for maximum precipitation of the natural AHG serum was the same as required for neutralization of the serum agglutinating natural anti-A-sensitized cells but only one-third was required for serum agglutinating cord anti-A-sensitized cells. The gamma globulin (1) serum, which was inactive with cells sensitized with natural anti-A, restored the agglutinating activity of the gamma-globulin-neutralized natural AHG (2a) serum.Electrophoretic studies showed that normal rabbit serum, natural AHG rabbit serum, and gamma globulin AHGG contained the same globulin components except for the alpha one fraction. Both the AHG sera were characterized by a new alpha component while the gamma globulin AHG showed an additional new alpha component. The significance of these findings is discussed.