CD4 and neoplasm: While tumors derived by injecting parental, MHC-II-negative cells showed very poor, if any, infiltration of lymphocytes and scarce presence of macrophage and neutrophils in several tumor models, CIITA-transfected MHC-II positive tumors were rapidly and firstly infiltrated by CD4+ T cells, followed by CD8+ T cells, and later by DC, macrophage, and neutrophils.