Hyper-immunoglobulin G2 production by B cells from patients with localized juvenile periodontitis and its regulation by monocytes

Localized juvenile periodontitis (LJP) runs in families, and a predisposition to develop disease appears to be inherited in an autosomal dominant fashion. Patients with LJP have elevated levels of serum immunoglobulin G2 (IgG2), and this is most striking in black LJP patients. We hypothesized that the markedly elevated serum IgG2 levels related to LJP status and race may be attributable to a fundamental difference in the response of black LJP leukocytes. To test this possibility, leukocytes from black LJP patients, black non-periodontitis (NP) controls, and white NP controls were cultured with a nonspecific mitogen (pokeweed mitogen) which stimulates immunoglobulin production. The levels of IgG2 produced were measured using an enzyme-linked immunosorbent assay. The results revealed that the serum IgG2 level differences among black LJP patients and white and black NP subjects were reproducible in peripheral blood leukocytes in vitro. Analysis revealed that B cells from the LJP patients appeared to be predisposed to produce high levels of IgG2. Further analysis supported the concept that the high IgG2 responses of B cells from black LJP patients were regulated by monocytes. Replacing the monocytes in cultures from white NP subjects with LJP monocytes from black patients resulted in production of IgG2 at levels that were comparable with those produced by the LJP B cells from black patients. In short, B cells from black LJP patients produce elevated levels of IgG2 in vitro, and at least part of this elevation appears to be attributable to regulation via the LJP monocytes.