Alveolar macrophages and mast cells mediate the early inflammatory and pro-allergic responses induced by rCNT. a,b: BAL and lung tissue were collected from C57BL/6 mice exposed to rCNT for 4 h and sacrificed either immediately or on the following day. Comparison of mRNA expression levels of cytokines/chemokines in BAL cells (a) and lung tissue (b) showing that pro-inflammatory cytokines Il-1β and Tnf-α are produced by alveolar macrophages which are the major cell type in BAL at early time points (data not shown) while Th2-promoting cytokine Il-33, and eosinophil-attracting chemokine Ccl17 are expressed in BAL cells as well as in other cells types present in lung tissue. c: levels of Th2 type cytokines Il-13 and Il-4 in lungs were dependent on the presence of mast cells as the expression of these cytokines was significantly lower in KitW-sh mice exposed to rCNT for 4 h and sacrificed on the next day. mRNA expression levels in a and b are presented as fold changes relative to untreated control mice (n = 5-8). In c, values indicate fold changes compared with control mice of the corresponding strain (n = 7-9). *P < 0.05; **P < 0.01; ***P < 0.001. C, untreated control group.