SELL and inflammatory bowel disease: Under the second Ags stimulation in the colonic tissue, Tcm cells lose the lymph node homing receptors CCR7 and CD62L (Sallusto et al., 2004), and transform into Tem cells, and form the colitogenic Tcm and/or Tem, and recirculate continuously between the blood, lymph, and colonic mucosa, to express high levels of inflammatory cytokines (as IL-2, IL-7, IL-12, and 1L-15 in Figure 4) that results in IBD.