Rap1a deficiency modifies cytokine responses and MAPK-signaling in vitro and impairs the in vivo inflammatory response

► Lack of the small GTPase rap1a causes an increase in MAP kinase signaling. ► Lack of rap1a leads to modification in cytokine expression and secretion. ► Rap1a-deficient mice show reduced responses in a contact hypersensitivity model. ► Rap1a is required for the fine-tuning of immunological responses.