TNF and rheumatoid arthritis: The prominent role played by tumor necrosis factor (TNF) α in inflammation and its relevance to AS and RA, as well as the location of the TNF-α gene (TNFA) within the class III region of MHC (between the HLA-B locus and HLA-DR) has led to great interest in the possibility that variants of the gene might be involved in disease susceptibility.