CD4 and melanoma: d) Treg cells stimulate PD-L1 expression in MDSCs, we know that Treg cells stimulate PD-L1 expression in MDSCs from melanoma mice, on the other hand, the VISTA, also designated as PD-1H, is a well-established negative-type immune regulator now known to modulate immune evasion in cancer; Therefore, in addition to PD-L1, it is generally possible to find high levels of VISTA expression in MDSCs, monocytes and blasts of myeloid-type neoplasms, but this expression was not found in CD4+, CD8+ lymphocytes or Treg cells in the acute phase of this disease.