CD4 and systemic sclerosis: No evidence exists for involvement of the ITGAL gene in PAH; however, a prior study reported a parallel hypomethylation and mRNA overexpression of the ITGAL gene in circulating CD4+ T cells isolated from 18 patients with systemic sclerosis (of which only one had PAH) vs. 15 CTRLs leading to immunological abnormalities and fibrotic processes [41].