Fig. 5. LTα₁β₂-LTβR axis controls thymic regeneration.

Total body irradiation induces the production of RANKL by radioresistant CD4⁺ SP thymocytes and LTi cells, which triggers the upregulation of LTα₁β₂ expression, mostly on LTi cells. Total body irradiation also enhances LTβR expression on all TEC subsets. LTα₁β₂-LTβR axis favors thymic regeneration and thereby enhances T-cell reconstitution trough (i) TEC recovery by stimulating their proliferation, differentiation and survival and (ii) the homing of lymphoid progenitor cells (LPC) by increasing the expression of CCL19 and CCL21 chemokines in TEC and P-selectin, ICAM-1 and VCAM-1 adhesion molecules on endothelial cells.