Immunoregulation in severe generalized periodontitis

Severe generalized periodontitis (SGP) is an inflammatory disease which leads to extensive alveolar bone loss in young adults. Peripheral blood lymphocytes from SGP patients have been previously reported to exhibit an in vitro hyperproliferative response when exposed to B cell mitogens derived from Staphylococcus aureus and Actinomyces viscosus. Therefore hyperresponsiveness to B-cell mitogens could be an important pathogenic factor in the susceptibility to and progression of SGP. We have tested whether the hyperproliferative response of lymphocytes from SGP patients was due to (i) a functional deficiency of suppressor T cells, or (ii) to numerical alterations of lymphocytes. Supernatant fluids from concanavalin A-stimulated T cells from 14 SGP patients and 14 normal subjects were compared for their ability to suppress the IgM synthesis of B-cell mitogen-stimulated mouse splenocytes. No significant differences were noted in suppressor T-cell function between control subjects and SGP patients. However, SGP patients had significantly higher lymphocyte counts than control subjects, and there was a positive correlation between high lymphocyte counts and high mitogen-stimulated proliferation. SGP patients also had higher lymphocyte:monocyte ratios than control subjects, suggesting that a defect in macrophage-mediated suppression might be involved in the hyperproliferation phenomenon. Our data do not support the hypothesis that a suppressor T-cell defect is the cause of mitogen-induced hyperproliferative responsiveness of peripheral blood lymphocytes from SGP patients. Rather, hyperproliferation may be due to an expansion of the lymphocyte pool which responds to mitogens, or/and a regulatory disturbance which arises because of altered lymphocyte:macrophage ratios.