CCL21 and thymus atrophy: Only the expression of the receptor Ccr7 is decreased after infection, although no alterations were observed on the expression in the thymus of its chemokine ligand Ccl21. This is in contrast with a previous report on sepsis-induced thymic atrophy, in which the authors show a down-regulation of the expression of CCR7, CCR9 and PSGL1 (41).