Figure 2a shows the frequencies of Treg in the PBMCs of CRC patients (n = 12, age range 58–80 years) compared with age-matched healthy controls (n = 11, age range 48–93 years) and patients with inflammatory bowel disease (n = 22, age range 19–80 years). In all groups, the frequency of Treg was less than 2% of CD4+ T cells. Here, CD4 is linked to inflammatory bowel disease.