Autophagy Contributes to the Induction of Anti-TNF Induced Macrophages

Background and Aims: Anti-tumour necrosis factor [TNF] antibodies induce regulatory macrophages which display a phenotype resembling M2 type macrophages. Anti-TNF induced macrophages [M phi ind] have immunosuppressive and wound healing properties. The factors that contribute to the induction of M phi ind 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 M phi ind. Methods: We studied the effect of autophagy on M phi ind in vitro using peripheral blood mononuclear cells. Interferon gamma [IFN-gamma] induced macrophages [M phi 1] were generated by culturing monocytes in the presence of IFN-gamma. M phi ind 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: M phi ind had a different expression profile of autophagy related transcripts with increased expression of 33/40 altered genes compared with M phi 1. In addition, autophagic activity was increased in M phi ind compared with M phi 1. Induction of M phi ind 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 M phi ind and inhibition resulted in decreased viability as well as decreased expression of CD206. Conclusions: M phi ind have increased levels of autophagy compared with inflammatory M phi 1, and the induction of these macrophages is impaired in donors carrying the T300A risk allele for the ATG16L1. Given the association between M phi ind 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.