mRNA expression and protein secretion of CCL20 by mast cells. (a) RNA samples from HMC-1 cells were analyzed by RT-PCR for CCL20, yielding PCR products of 216 and 269 bp for CCL20 and β2M, respectively. Note the prominent single products at the appropriate sizes. Lanes 1 and 2, CCL20; lanes 3 and 4, β2M. (b) Supernatants from HMC-1 cells stimulated with A23187 (10−6 M) and PMA (10−7 M) for 24 h were analyzed for CCL20 by Western blotting. Lane 1, human recombinant CCL20; lanes 2 and 3, supernatants from A23187- and PMA-treated HMC-1 cells from two independent experiments. (c) CCL20 production by human mast cells. HMC-1 cells were stimulated with A23187 (10−6 M) and PMA (10−7 M) for 1 to 24 h. Cell-free supernatants were used to test CCL20 levels by ELISA. Results are the means ± standard errors of the means for three experiments.