Interactions of porcine IgG and porcine lymphocytes with protein-A Sepharose

Interaction of Protein-A Sepharose with porcine IgG showed that the binding capacity for porcine IgG was slightly lower than for human IgG. A small proportion of antibody activity of porcine serum was not reactive with Protein-A Sepharose. The interaction occurred with Fc fragments obtained either by papaĭn or by trypsin splitting of IgG but not with Fc' fragments. However, Fab fragments obtained after papaĭn or trypsin hydrolysis as well as Fab'₂ and Fab' fragments obtained by pepsin cleavage were partly retained onto the Protein-A Sepharose column. No antigenic differences were observed between retained and non-retained Fab, Fab' and Fab'₂ fragments with specific anti-porcine light chain antiserum. Thus, the interaction between Protein-A from S. aureus and porcine IgG is mediated not only through the Fc fragment, but also partly through the Fab part of the molecule. The resolubilized heavy chains did not bind to Protein-A Sepharose, suggesting that structural requirements are necessary for recognition. A subpopulation of porcine lymphocytes could be adsorbed onto Protein-A Sepharose beads, a binding specifically inhibited in the presence of porcine IgG.