CD4 and neoplasm: We have recently generated a novel from of 4-1BBL chimeric with streptavidin (SA-4-1BBL) and demonstrated its robust costimulatory activity on CD4+ T and CD8+ T cells, which translated into therapeutic efficacy in various tumor models when SA-4-1BBL was used as adjuvant component of TAA-based vaccines [24], [25], [28], [30].