Jacalin, a jackfruit lectin, precipitates IgA1 but not IgA2 subclass on gel diffusion reaction.

Precipitation reaction in agarose gel between jacalin, a lectin from jackfruit seeds, and purified immunoglobulins of various classes and their components was studied. Single precipitation arcs were observed with monomeric and dimeric IgA1 subclass as well as secretory IgA1, but not with IgA2 of both allotypes, IgG, IgM, IgD, IgE, free secretory component or with the J chain. Thus, jacalin can be used for differentiating IgA1 from IgA2 subclass by a simple agarose gel diffusion.