Role of the phosphoinositide 3‐kinase p110δ in generation of type 2 cytokine responses and allergic airway inflammation

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Abstract
Phosphoinositide 3-kinases (PI3K) regulate immune activation via their roles in signal transduction of multiple classes of receptors. Here, we examined the effect of genetic inactivation of the hemopoietic cell-restricted PI3K isoform p110δ on systemic cytokine and chemokine responses and allergic airway inflammation. We found that type 2 cytokine responses (IL-4, IL-5 and IL-13) are significantly decreased in p110δ mutants, whereas type 1 cytokine responses (IFN-γ and CXCL10) were robust. Elevated IFN-γ production during the primary response to ovalbumin (OVA) was associated with reduced production of the regulatory cytokine IL-10. IFN-γ and IL-10 production normalized after secondary OVA immunization; however, type 2 cytokine production was persistently reduced. Type 2 cytokine-dependent airway inflammation elicited by intranasal challenge with OVA was dramatically reduced, with reduced levels of eosinophil recruitment and mucus production observed in the lungs. Induction of respiratory hyper-responsiveness to inhaled methacholine, a hallmark of asthma, was markedly attenuated in p110δ-inactivated mice. Adoptive transfer of OVA-primed splenocytes from normal but not p110δ-inactivated mice could induce airway eosinophilia in naive, airway-challenged recipient mice. These data demonstrate a novel functional role for p110δ signaling in induction of type 2 responses in vivo and may offer a new therapeutic target for Th2-mediated airway disease.