Passive Transfer of Tumour‐Derived MDSC s Inhibits Asthma‐Related Airway Inflammation

Myeloid‐derived suppressor cells ( MDSC s), a heterogeneous population including myeloid progenitor and immature myeloid cells, are known to inhibit T cell responses. The issue of whether tumour‐derived MDSC s regulate the immune response in an asthma environment is currently unclear. Here, we have reported that tumour‐derived MDSC s shift the balance back to normal in a T h2‐dominant asthmatic environment. In an ovalbumin ( OVA )‐induced mouse asthma model, injected tumour‐derived MDSC s were recruited to the lungs of asthmatic mice by CC chemokine ligand 2 ( CCL 2). MDSC s transferred into asthmatic mice via i.v. injection suppressed the infiltration of inflammatory cells into the lung, the T h2 cytokine, IL ‐4, concentration in bronchial lavage fluid and the serum level of OVA ‐specific I g E . Increased TGF ‐ β 1 production in the lung was detected after transfer of MDSC s. The inhibitory effects of MDSC s were reversed upon treatment with an anti‐ TGF ‐ β 1 antibody, suggesting dependence of these activities on TGF ‐ β 1. Our findings imply that tumour‐derived MDSC s inhibit the T h2 cell‐mediated response against allergen in a TGF ‐ β 1‐dependent manner. Based on the collective results, we propose that asthma may be effectively targeted using a novel MDSC ‐based cell therapy approach.