[Detection of IgG fraction of intact rabbit serum interacting with chromatin]

It was shown that the intact rabbit sera interact with chromatin and thymocyte nuclei in a quantitative reaction of complement fixation and immunoluminescence analysis, respectively. Purified immunoglobulins G (IgG) and Fab fragments isolated from them were also found capable of such interactions. The interactions are not caused by Ig aggregate absorption on chromatin and can be due to the presence of natural antibodies against chromatin in the 7S fraction of intact rabbit IgG. These IgG possess heterogeneous charges, presumable due to the presence of antibodies against various antigenic chromatin determinants in rabbit serum.