CD4 and systemic lupus erythematosus: When investigating the mechanism of NKG2D+CD4+T cells in SLE, Yang et al. [48] found that NKG2D expression could be induced on normal CD4+ T cells by co-culturing them with monocytes from SLE patients; the induced NKG2D+CD4+ T cells were involved in the pathogenesis of SLE in the form of NKG2D-MIC interactions with CD14+ monocytes.