Elevated numbers of plasma cells are associated with localized and chronically inflamed gingiva of patients with adult periodontitis. However, only limited information is currently available as to how cytokines produced by CD4+ T cells are involved in these increased B cell responses in affected gingival tissues. When gingival mononuclear cells (GMC) were isolated from inflamed tissues and examined by flow cytometry, ~20-30% of lymphocytes were CD4+ T cells. For the analysis of Th1 and Th2 cytokine expression by these CD4+ T cells, RNA was extracted and reverse transcriptase-polymerase chain reaction (RT-PCR) was performed by using specific 5' and 3' primers for interferon-gamma (IFN-γ) and IL-2 (Th1), IL-4, IL-5, IL-6, IL-10 and IL-13 (Th2) and p-actin (internal control). Two distinct cytokine profiles were noted based on the expression of selected Th1 and Th2 cytokines, where one pattern was represented by expression of mRNA for IFN-γ, IL-6, IL-10 and IL-13, while the second consisted of mRNA for IFN-γ, IL-6 and IL-13. In most samples, mRNA for IL-2, IL-4 and IL-5 were not detected by cytokine-specific RT-PCR. When RNA was isolated from CD4+ T cells of concanavalin A-stimulated peripheral blood mononuclear cells (PBMC) of the same patients and examined by RT-PCR, mRNA for all Th1 and Th2 cytokines were detected. These findings suggest that although human CD4+ T cells are capable of producing an array of Th1- and Th2-type cytokines, the CD4+ T cells associated with periodontitis are limited to production of IFN-γ, IL-6, IL-13 and in some instances IL-10. CD4+ T cells from diseased periodontal tissues are divisible into two groups based upon whether or not IL-10 is produced, together with IFN-γ, IL-6 and IL-13.