CD4 and Crohn disease: In addition, they found that the proportions of HLA-DR+ T cells were correlated in both CD4+ and CD8+ T cell populations in patients with IBD.[46] In addition, as a member of class II major histocompatibility complex (MHC) proteins,[47] studies indicate that HLA-DR is closely associated with Crohn disease, and that Crohn disease susceptibility may be associated with specific allotypes of the human MHC.[48] Consequently, it may be concluded that an increase in HLA-DR+ CD4+ T cells contributes to the development of Crohn disease.