These B lymphoid-like cells are a major source of Ido1 in some tumors and have immunosuppressive activity on T cells.66 Interestingly, the Ido1 pathway could also prevent complement deposition in tumors.55 It has been shown that pharmacological or genetic Ido1 inhibition combined with chemo-radiotherapy resulted in extensive complement deposition in mouse brain tumors.67 It is therefore possible that complement deposition is reduced in Tyk2Δ/Δ tumors. This evidence concerns the gene IDO1 and brain neoplasm.