Antibodies in rabbits immunized with cationized IgG react with histones H3 and H4

Abstract

Objective: Rabbits immunized with cationized rabbit IgG develop antinuclear antibodies. This study was aimed at identifying the reactive antigens.

Methods: Rabbits were immunized with homotypic or allotypic IgG that were physicochemically altered to produce positively charged dimethylpropanamide (polycationic) side chains.

Results: Seven of 11 rabbits injected with cationized IgG produced antinuclear antibodies detected by indirect immunofluorescence. By enzyme-linked immunosorbent assay, these were IgG antibodies reacting with histone (H3-H4)2 tetramer and with individual histone polypeptides H3 and H4. The antihistone antibodies were absorbed by cationized IgG but not by normal IgG.

Conclusion: Cationized IgG appears to possess antigenic determinants of sufficient similarity to produce antibody responses cross-reactive with histones H3 and H4.