Involvement of CD244 in Regulating CD4+ T Cell Immunity in Patients with Active Tuberculosis

CD244 (2B4) is a member of the signaling lymphocyte activation molecule (SLAM) family of immune cell receptors and it plays an important role in modulating NK cell and CD8(+) T cell immunity. In this study, we investigated the expression and function of CD244/2B4 on CD4(+) T cells from active TB patients and latent infection individuals. Active TB patients had significantly elevated CD244/2B4 expression on M. tuberculosis antigen-specific CD4(+) T cells compared with latent infection individuals. The frequencies of CD244/2B4-expressing antigen-specific CD4(+) T cells were significantly higher in retreatment active TB patients than in new active TB patients. Compared with CD244/2B4-dull and -middle CD4(+) T cells, CD244/2B4bright CD4(+) T cell subset had significantly reduced expression of IFN-gamma, suggesting that CD244/2B4 expression may modulate IFN-c production in M. tuberculosis antigen-responsive CD4(+) T cells. Activation of CD244/2B4 signaling by crosslinking led to significantly decreased production of IFN-gamma. Blockage of CD244/2B4 signaling pathway of T cells from patients with active TB resulted in significantly increased production of IFN-gamma, compared with isotype antibody control. In conclusion, CD244/2B4 signaling pathway has an inhibitory role on M. tuberculosis antigen-specific CD4(+) T cell function.