Figure 1.

H₄ receptor expression is restricted to eosinophils and dendritic cells. (a) RT–PCR detection of H₄ receptor mRNA in different purified cell types and cell lines. Total RNA from different cell types were reversed transcribed and used as templates for PCR. (b) Human eosinophils express H₄ but not H₃ receptors. H₃ or H₄ receptor mRNA in human eosinophils was detected by RT–PCR using specific primers. For both (a) and (b), 25 PCR cycles were performed for the amplification of the H₄ receptor. Human SK-N-MC cells transfected with the H₁, H₂, H₃ or H₄ receptor were used as controls for specificity of histamine receptor detection. G3PDH mRNA in RNA samples was amplified with specific primers as controls in PCR reactions.