Figure 1. Subsets of TM cells. There are 3 major subsets of TM cells: TCM, TEM and TRM. These subsets are identified on the basis of differential expressions in several chemokine receptors and adhesion molecules. While TCM cells express high levels of CCR7 and CD62L (L-selectin) (CCR7hiCD62Lhi), TEM cells express low levels of CCR7 and CD62L (CCR7loCD62Llo). These phenotypes indicate that TCM cells circulate to SLOs, whereas TEM cells circulate to peripheral organs. TRM cells express low levels of CCR7 and high levels of CD69 and CD103 (CCR7loCD69hiCD103hi) to remain in peripheral organs.
