CSF2 and melanoma: Because the acute biologic effects of GM-CSF on myeloid cell populations can be dose-dependent, with excessive doses generating MDSCs rather than activating antigen presenting cells [23], we evaluated the impact of Melanoma GVAX on the absolute numbers and proportions of circulating monocytes and MDSCs in blood collected before and 2 days after the first and fourth Melanoma GVAX treatment cycles.