CD4 and rheumatoid arthritis: Peripheral Vγ9Vδ2 T cells after stimulation with IPP in vitro are shown to upregulate the expression of APC specific molecules HLA-DR and CD80/86 and presented soluble antigens and synthetic peptides to CD4+ T cells and B cells thus contributing to activation of CD4+ T cells and being associated with RA onset and disease progression (100).