Treatment of an immortalized APC cell line with both cytokines and LPS ensures effective T-cell activation in vitro.

Antigen-presenting cells (APCs) are crucial for the generation of a functional immune response to pathogens. Furthermore, there is abundant evidence for their importance in primary T-cell activation, B-cell maturation and maintenance of an ongoing immune response. In the present study, we have analysed phenotypic characteristics and functionality of a p53-deficient APC cell line (JawsII) derived from mouse bone marrow culture. We show that unstimulated JawsII cells express low surface levels of major histocompatibility complex (MHC) and costimulatory molecules, both of which can be upregulated upon treatment with cytokines in vitro. Cytokine stimulation also leads to an enhanced T-cell activation capacity but has only little effect on cytokine release by the JawsII cells themselves. On the contrary, stimulation of the JawsII cells with lipopolysaccharide (LPS) leads to the production and secretion of high amounts of interleukin-1 (IL-1), IL-6 and tumour necrosis factor-alpha (TNF-alpha) but no increase in the surface levels of MHC and costimulatory molecules, and has only little effect on the T-cell activation capacity. Our data suggest that the effects observed upon treatment with cytokines or LPSs are complementary, and that both stimuli are needed for mediating a strong and efficient JawsII cell-dependent T-cell activation.