FOXP3 and squamous cell carcinoma: VISTA is expressed on tumour-infiltrating lymphocytes (TILs), myeloid-derived suppressor cells and regulatory T cells (MDSCs), regulatory T cells (CD4+CD25+Foxp3+Treg), dendritic cells (DCs), tumour associated macrophages (TAMs/MФ) and neoplastic squamous carcinoma cells [418,419].