The effect of limited fragmentation of porcine 19s immuno globulin m on agglutination and complement fixation evidence that at least 2 intact subunits are required for complement fixation by immuno globulin m antibody antigen complexes
Beale, D.; Kent, C.M.
Biochimica et Biophysica Acta 533(1): 23-33
ISSN/ISBN: 0005-2728 Accession: 006647893
Limited fragmentation of pig Ig[immunoglobulin]M anti-Salmonella with pepsin gave a 12S product which agglutinated Salmonella almost as efficiently as the original IgM, but the complement [C] fixing ability of the complexes was substantially lowered. The 12S product consisted of molecular entities having intact Fc regions with an average of 3 or 4 intact Fab arms still attached. Removal of Fab arms by pepsin was apparently a random process, and on this basis a mathematical model was set up. From this model it was possible to calculate the frequencies of molecular entities which would give rise to the observed average of 3 or 4 Fab arms. Complexes probably need to be formed by molecules having at least 2 intact subunits before efficient C fixation takes place.