Here we tested the potential of combining anti-CD200R and anti-PD-1 immune checkpoint blockade, since (i) the human studies clearly suggested a tumour-promoting role of CD200R, (ii) most mouse studies describing tumouricidal effects of CD200R relied on examining the effects of gene deletion or over-expression rather than antibody-based interventions, and (iii) a majority of reports focused on either single gene perturbations or antibody monotherapies. The gene discussed is CD200R1; the disease is neoplasm.