CXCR5 and listeriosis: found that CD4+ Tem (CXCR5−CCR7−) cells primarily gave rise to CXCR5− (Th1) secondary effector cells, while Tcm (CXCR5+CCR7+) cells gave rise to both CXCR5+ (Tfh) and CXCR5− (Th1) secondary effector cells in response to Listeria monocytogenes infection (2).