B2M and metastatic melanoma: Since β2M is an essential component of MHC-I antigen presentation to CD8+ T cells in the context of tumor immunity (36), and downregulation of HLA-I has been associated with deficient expression of β2M in ICT-resistant metastatic melanoma patients (8), we sought to evaluate whether CD1d, CD1b, and FCGRT, could also be associated with β2M-dependent ICT resistance.