Autophagy contributes to the induction of anti-TNF induced macrophages

Abstract

Background and Aims: Anti-tumour necrosis factor [TNF] antibodies induce regulatory macrophages which display a phenotype resembling M2 type macrophages. Anti-TNF induced macrophages [Mφind] have immunosuppressive and wound healing properties. The factors that contribute to the induction of Mφind remain to be explored. Autophagy has been described as a factor that is important for the induction and function of M2 type macrophages. We studied the contribution of autophagy to the induction of Mφind. Methods: We studied the effect of autophagy on Mφind in vitro using peripheral blood mononuclear cells. Interferon gamma [IFN-γ] induced macrophages [Mφ1] were generated by culturing monocytes in the presence of IFN-γ. Mφind were generated by performing mixed lymphocyte reactions [MLR] in the presence of anti-TNF antibodies; 28 healthy donors were genotyped for rs_2241880 [ATG16L1]. Cells were analysed by autophagy gene array, immunofluorescence, western blot, flowcytometry, 3H-thymidine incorporation and MTS assay. Results: Mφind had a different expression profile of autophagy related transcripts with increased expression of 33/40 altered genes compared with Mφ1. In addition, autophagic activity was increased in Mφind compared with Mφ1. Induction of Mφind was positively correlated to the number of wild-type alleles for the ATG16L1 T300A risk allele present in the culture. Finally, the autophagy-related protein cathepsin S was highly expressed in Mφind and inhibition resulted in decreased viability as well as decreased expression of CD206. Conclusions: Mφind have increased levels of autophagy compared with inflammatory Mφ1, and the induction of these macrophages is impaired in donors carrying the T300A risk allele for the ATG16L1. Given the association between Mφind and clinical response, this suggests that an intact autophagy pathway may be important for an optimal response to anti-TNF therapy in inflammatory bowel disease.