CTLA4 and metastatic melanoma: For instance, flow cytometric analysis of peripheral blood mononuclear cells (PBMCs) from 36 metastatic melanoma patients revealed increased frequency of ICOS + CD4 T cells following treatment with anti-CTLA-4, suggesting that this effector T cell population may function as a pharmacodynamic marker of anti-CTLA-4 therapy (Ng Tang et al. 2013).