CD8+, CD4+, and CD4+/FoxP3+ T-cells are present in the majority of patients [84], but the number of T-reg cells in pleural effusions of MPM patients is lower than in other solid tumors [85], confirming the presence of an immunosuppressive milieu in MPM tumoral mass, rather than in pleural effusion [86]. This evidence concerns the gene FOXP3 and Pleural effusion.