While it has been previously shown that IL-5 expression in Th2 cells is limited to the effector memory subset whereas IL-4 is expressed in both central and effector memory subsets [4], this finding that IL-10 and TGFβ signaling may be critical to Th2 subpopulation expansion provide new insight into the interrelationship between the IL-5+ and IL-5−Th2 subpopulations and provides new avenues for the study of filarial-specific immune regulation and protection from immune-mediated pathology in LF. Here, IL4 is linked to Lassa fever.