PDCD1 and melanoma: The lymphocyte expression of these receptors was further increased following ILP with similar results observed for PD-1 on CD4+ T cells, which is in agreement with a previous study.13 In analogy with these in vivo findings, results achieved using an in vitro model of ILP suggested that PBMCs cultured in the presence of melphalan-exposed melanoma cells expressed higher densities of CXCR3, CCR4, CCR5 and PD-1 than did PBMCs cultured with non-exposed melanoma cells.