CD4 and rheumatoid arthritis: At a functional level, from the 3 synovial myeloid cell subsets isolated ex vivo from RA SF samples, Mo and CD1c+ cDC were both capable of inducing proliferation of allogeneic CD4+ T cells and capable of inducing the activation of a significant portion of these T cells acquiring a Th1-like IFN-γ+IL-17– phenotype (Supplemental Figure 6, B and C).