As FALCs within the pericardium and mediastinum are key sites for local IgM secretion within the pleural cavity [5] and expansion of mediastinal FALCs has been shown in an MRL/MpJ-lpr autoimmune mouse model of SLE [20] we aimed to determine whether these structures are activated during pristane induced pleuritis. Here, CD40LG is linked to systemic lupus erythematosus.