PD-L1 is expressed on activated T cells and is required for T cell conditioning and dendritic cell maturation.50 However, its expression on T cells has been mostly linked to inhibition of their responses.51 Other studies indicates that expression of PD-L1 on CD8+ and CD4+ T cells correlates with patient response to ICB, suggesting PD-L1 expression in CD8+ T cells as a prognostic marker in melanoma.9,52. Here, CD4 is linked to melanoma.