Rat C3 conversion by rat anti-2,4,dinitrophenyl (DNP) hapten IgA immune precipitates.
Monomeric (m-) and polymeric (p-) anti-DNP monoclonal (MC) rat IgA antibodies (Ab) were tested for precipitation with DNP-bovine serum albumin (DNP-BSA) and C3 conversion in rat serum, with rat MC anti-DNP IgG2b used as reference. At equivalence, p-IgA rapidly precipitated DNP-BSA, with little antigen (Ag) left in the supernatant. In contrast, m-IgA at five-fold higher concentration precipitated Ag very slowly, with less than 50% of Ag precipitated at equivalence. The Ag/Ab weight ratio at equivalence was 0.13 for both m- and p-IgA, but the molar ratio was 0.3 for m-IgA and close to 1.0 for p-IgA, suggesting a higher avidity of p-IgA. Rat C3 conversion by rat IgA immune precipitates (IP) was about 20% with m-IgA and 40% with p-IgA. EGTA did not significantly affect these figures. Therefore, rat MC IgA IP activated the rat alternative C pathway. Neither rat nor mouse IgA anti-DNP IP activated C3 in normal human serum.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000915:Antibody Affinity; D003167:Complement Activation; D003176:Complement C3 / Q000276:immunology*; D003168:Complement Fixation Tests; D004136:Dinitrobenzenes / Q000276:immunology*; D006168:Guinea Pigs; D006241:Haptens; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology*; D008970:Molecular Weight; D009578:Nitrobenzenes / Q000276:immunology*; D011233:Precipitin Tests; D051381:Rats
D000911:Antibodies, Monoclonal; D003176:Complement C3; D004136:Dinitrobenzenes; D006241:Haptens; D007070:Immunoglobulin A; D009578:Nitrobenzenes