Phenotype of blood CD4+ T cells in properdin-deficient and wild-type mice. (A) Peripheral CD4+ T cells from arthritic properdin-deficient mice showed lower expression of CD69 compared with WT CAIA lymphocytes. Data represent the mean ± SD of positive cells from three experiments involving five mice/group. *P < 0.05; **P < 0.01; Student t test. (B) CD4+ RANKL+ T cells in blood of CAIA KO mice were fewer than those in the CAIA WT group. The data are expressed as the mean ± SD of positive cells from three experiments involving five mice/group.*P < 0.05; **P < 0.01; and ***P < 0.001; Student t test. Histograms show RANKL expression on CD4+ T cells from properdin-deficient and wild-type mice in one individual experiment. (C) Blood CD4+ T cells from wild-type mice were more sensitive to Con A stimulation than were those from properdin-deficient mice and had significantly higher intracellular levels of IFN-γ and IL-17. CD4+ T cells were isolated at Day 10 of CAIA and stimulated with Con A (2 μg/ml). After 48 hours of culture, cells were restimulated with PMA and ionomycin and subjected to flow-cytometry analyses for the expression of IL-17 and IFN-γ. Data represent the mean ± SD of single IL-17 or IFN-γ producers of three experiments involving five mice/group. *P < 0.05; **P < 0.01; ***P < 0.001; Student t test. (D) One representative experiment showing the lack of significant IL-4 production in Con A-stimulated CAIA KO and WT cells. The intracellular level of IFN-γ and IL-17 in activated arthritic properdin-deficient CD4+ T lymphocytes was lower than that in the CAIA WT group.