The binding of jacalin with rabbit immunoglobulin G

Rabbit immunoglobulin G (IgG) was subjected to affinity chromatography on a column of jacalin-Sepharose 4B. While the majority of IgG molecules did not bind, a small fraction, representing about 25% of the total IgG applied, bound to jacalin-Sepharose 4B. The binding of rabbit IgG to jacalin was further evidenced by ELISA performed on jacalin coated microtitre plates. While the jacalin-retained IgG fraction displayed strong binding, the unretained fraction did not demonstrate any detectable binding. Upon SDS-PAGE, both the jacalin retained and unretained rabbit IgG fractions displayed identical protein profiles. Upon protein blotting it was demonstrated that jacalin binding sites were located only on the heavy chain of IgG. These results suggest that rabbit IgG molecules are heterogeneous with respect to their glycosylation patterns. A small fraction of rabbit IgG molecules binds jacalin and the process is probably mediated through O-linked oligosaccharides present on the heavy chain of IgG.