Previous studies of Ag-specific T cells studies revealed that a systemic Lm-2W1S infection initiates a Th1-biased T cell response where (i) some TN cells differentiate as CXCR5-ve cells, expressing T-bet and CD25 (IL-2Rα), which support the Th1 program and revert to Tem memory T cells once the infection is cleared, and (ii) CXCR5+ve cells which expand in response to TCR signaling, but evade Th1 differentiation and develop as Tcm cells lacking CD25 expression (26). Here, CXCR5 is linked to infection.