TAGAP and multiple sclerosis: T-cell activation Rho GTPase-activating protein (TAGAP) is associated with the susceptibility to many autoimmune diseases, including IBD, multiple sclerosis, psoriasis, rheumatoid arthritis and celiac disease (Smyth et al., 2008; Raychaudhuri et al., 2009; Franke et al., 2010; Tsoi et al., 2012), based on a number of genomic studies investigating the effects of single nucleotide polymorphisms (SNPs) near or within the TAGAP gene locus.