CCR2 and infection: The relatively long time to death of CCR2 mice given lower doses of LVS ID (Figs 1 and 3 and S4 File) raised the possibility that, in addition to CCR2’s role during innate immune responses, susceptibility was also related to poor development of T cell-mediated adaptive immune responses; T cell activities are necessary to clear primary LVS ID infections and establish protection against secondary challenge [14,15].