CD 41 is a reliable identification and activation marker for murine basophils in the steady state and during helminth and malarial infections

Basophils, a rare leukocyte population in peripheral circulation, are conventionally identified as CD 45 int CD 49b + Fcε RI + cells. Here, we show that basophils from blood and several organs of naïve wild‐type mice express CD 41, the α subunit of α IIb β 3 integrin. CD 41 expression on basophils is upregulated after in vivo IL ‐3 treatment and during infection with N ippostrongylus brasiliensis ( N b). Moreover, CD 41 can be used as a reliable marker for basophils, circumventing technical difficulties associated with F cε RI for basophil identification in a N b infection model. In vitro anti‐ I g E cross‐linking and IL ‐3 basophil stimulation showed that CD 41 upregulation positively correlates with augmented surface expression of CD 200 R and increased production of IL ‐4/ IL ‐13, indicating that CD 41 is a basophil activation marker. Furthermore, we found that infection with P lasmodium yoelii 17X ( P y17x) induced a profound basophilia and using M cpt8 DTR reporter mice as a basophil‐specific depletion model, we verified that CD 41 can be used as a marker to track basophils in the steady state and during infection. During malarial infection, CD 41 expression on basophils is negatively regulated by IFN ‐γ and positively correlates with increased basophil IL ‐4 production. In conclusion, we provide evidence that CD 41 can be used as both an identification and activation marker for basophils during homeostasis and immune challenge.