Passive Transfer of Tumour‐Derived MDSCs Inhibits Asthma‐Related Airway Inflammation

Myeloid‐derived suppressor cells (MDSCs), a heterogeneous population including myeloid progenitor and immature myeloid cells, are known to inhibit T cell responses. The issue of whether tumour‐derived MDSCs regulate the immune response in an asthma environment is currently unclear. Here, we have reported that tumour‐derived MDSCs shift the balance back to normal in a Th2‐dominant asthmatic environment. In an ovalbumin (OVA)‐induced mouse asthma model, injected tumour‐derived MDSCs were recruited to the lungs of asthmatic mice by CC chemokine ligand 2 (CCL2). MDSCs transferred into asthmatic mice via i.v. injection suppressed the infiltration of inflammatory cells into the lung, the Th2 cytokine, IL‐4, concentration in bronchial lavage fluid and the serum level of OVA‐specific IgE. Increased TGF‐β1 production in the lung was detected after transfer of MDSCs. The inhibitory effects of MDSCs were reversed upon treatment with an anti‐TGF‐β1 antibody, suggesting dependence of these activities on TGF‐β1. Our findings imply that tumour‐derived MDSCs inhibit the Th2 cell‐mediated response against allergen in a TGF‐β1‐dependent manner. Based on the collective results, we propose that asthma may be effectively targeted using a novel MDSC‐based cell therapy approach.