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 [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.