Rat C3 Conversion by Rat Anti‐2,4, Dinitrophenyl (DNP) Hapten IgA Immune Precipitates

Publisher Website
Google Scholar
Abstract
Moncmeric (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 <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.