Th1-and Th2-cell commitment during infectious disease: asymmetry in divergent pathways

The development of T helper 1 (Th1) versus Th2 cells is a major branch point in the immune response. It is an important determinant of whether the response to an infectious pathogen will lead to protection of the host or dissemination of the disease. Recent studies have suggested that this process is governed by distinct sets of signals provided by dendritic cells upon interactions with specific infectious agents. A model is proposed that links together the pathogen,the innate response and Th-cell polarization.