activation of murine dendritic cells and macrophages induced by salmonella enterica serovar typhimurium macrophages and dendritic cells dcs are antigenpresenting cells apcs and the direct involvement of both cell types in the immune response to salmonella has been identified in this study we analysed the phenotypic and functional changes that take place in murine macrophages and dcs in response to live and heatkilled salmonella enterica serovar typhimurium both types of cell secreted proinflammatory cytokines and nitric oxide no in response to live and heatkilled salmonellae bacterial stimulation also resulted in upregulation of costimulatory molecules on macrophages and dcs the expression of major histocompatibility complex mhc class ii molecules by macrophages and dcs was differentially regulated by interferon ifngamma and salmonellae live and heatkilled salmonellae as well as lipopolysaccharide lps inhibited the upregulation of mhc class ii expression induced by ifngamma on macrophages but not on dcs macrophages as well as dcs presented salmonelladerived antigen to cd4 t cells although dcs were much more efficient than macrophages at stimulating cd4 tcell cytokine release macrophages are effective in the uptake and killing of bacteria whilst dcs specialize in antigen presentation this study showed that the viability of salmonellae was not essential for activation of apcs but unlike live bacteria prolonged contact with heatkilled bacteria was necessary to obtain maximal expression of the activation markers studied