In this protocol we describe how to process tumor tissues, spleens and lymph nodes to prepare single cell suspensions and extract lymphoid and myeloid immune cell populations such as naïve, activated, effector and memory subsets of CD8+ and CD4+ T cells, regulatory T cells (Tregs), CD11b- NK cells, mature B cells, dendritic cell (DC) subsets, M1- and M2-like macrophages, polymorphonuclear leukocytes (PMNs) and myeloid derived suppressor cells (MDSCs). This evidence concerns the gene CD4 and neoplasm.