Echinacea extracts have traditionally been used in the treatment of many infectious and other diseases (such as rhinovirus colds), and research has revealed the presence of various bioactivities in these extracts, particularly those connected with immune responses. We examined the effects of Echinacea by using gene expression analysis in a line of human bronchial epithelial cells, with or without rhinovirus infection. More than 13 000 human genes were evaluated. From these analyses we focused primarily on immune response genes and found that both Echinacea extracts, one predominantly rich in polysaccharides and the other rich in alkylamides and caffeic acid derivatives, stimulated the expression of numerous genes. These included a number of cytokines and chemokines, although the pattern of stimulation was different. In addition, Echinacea extracts tended to neutralize the effects of the rhinovirus. When the immune response gene pathways were analyzed with the Ingenuity Pathway program, it became apparent that many of them were interconnected through a major node, the transcription factor C/EBPbeta (CAAT/enhancer-binding protein beta) and its related C/EBP proteins. This suggests that Echinacea can bring about important biological responses in cells by virtue of interactions between components of the extract and a small number of intracellular factors involved in multiple signaling pathways.