Cytokine production and T-cell activation by macrophage–dendritic cells generated for therapeutic use

Clinical grade ex vivo-generated antigen-presenting cells, macrophage–dendritic cells (MAC–DCs) or macrophage-activated killers (MAKs) were derived from peripheral blood mononuclear cells (PBMCs). Cultures (7 d) were performed in non-adherent conditions in the presence of granulocyte–macrophage colony-stimulating factor (GM-CSF) and either interleukin 13 (IL-13) or dihydroxy-vitamin D₃ respectively. MAKs were activated during the last 24 h with interferon γ (IFNγ). Reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) analyses indicated that IL-1β and tumour necrosis factor α (TNFα) were produced by both cells. Higher pro-inflammatory cytokine (IL-1β and TNFα) amounts were detected on average in MAK supernatants. In contrast, IL-12 p40 was found only in MAC–DC supernatants, but the biologically active IL-12 form (p70) was never detected. T-cell cytokines (IL-2, IL-4, IL-10) were not produced in culture conditions in which T cells were nevertheless present. At d 7, TNFα or lipopolysaccharide (LPS) upregulated IL-12 p40 production by MAC–DCs, while IL-12 p70 remained undetectable. LPS stimulation also increased TNFα production by these cells. Allogeneic mixed lymphocyte reactions (MLR) showed that MAKs are poor stimulatory cells compared with MAC–DCs. The MAC–DC stimulatory capacity was enhanced by LPS, although the expression of HLA class II, CD83, CD80 and CD86 was unmodified. Thus, MAC–DCs represent a tool for triggering adaptative immunity, while MAK should be primarily used as effector killer cells.