There is provided inter alia according to the invention an ex vivo method of obtaining tolerogenic antigen presenting cells (APCs) that have the capability to induce tolerance in the immune system to an antigen, the method comprising (a) isolating monocytes from a sample obtained from a mammal; and (b) culturing the isolated monocytes in a cell culture to induce differentiation of the monocytes into antigen presenting cells having a tolerogenic phenotype, wherein the cell culture comprises (i) retinoic acid and TGFbeta, (ii) retinoic acid, TGFbeta and an AhR agonist or (iii) retinoic acid and an AhR agonist.