CD4+ T cells select unique P65, IRF1 and FOS dependen responses in APC for integration into antiviral CD8+ T cell immunity

Antiviral CD8+ T cell immunity depends on the integration of varying contextual cues, but how antigen presenting cells (APC ) consolidate these signals for decoding by T cells remains unclear. We describe gradual IFN-α/β-induced transcriptional adaptations that endowed APC with the capacity to rapidly activate the transcriptional regulators P65, IRF1 and FOS upon CD4+ T cell-mediated CD40 stimulation. While these responses operated through broadly utilized signaling components, they induced a unique set of costimulatory molecules and soluble mediators that could not be elicited by IFN-α/β or CD40 alone. This response was critical for the acquisition of antiviral CD8+ T cell effector function, and its activity in APC from patients infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) correlated with milder disease. These observations uncover a sequential integration process whereby APC rely on CD4+ T cells to select the innate circuits that guide antiviral CD8+ T cell responses. Cleavage under targets and tagmentation (CUT&Tag) for the transcription factor IRF1 in stimulated BM-derived cDC1.