CD4 and inflammatory bowel disease: We detected the expression of CRAF, ERK1/2, and LKB1 in PB‐CD4+ T cells of IBD patients and healthy donors by qRT‐PCR, and observed that the expression of CRAF, ERK1/2, and LKB1 was downregulated in IBD PB‐CD4+ T cells (Figure 8A–D).