DEVELOPMENT OF TH1 CD4+ T-CELLS THROUGH IL-12 PRODUCED BY LISTERIA-INDUCED MACROPHAGES

Development of the appropriate CD4+ T helper (T(H)) subset during an immune response is important for disease resolution. With the use of naive, ovalbumin-specific alphabeta T cell receptor transgenic T cells, it was found that heat-killed Listeria monocytogenes induced T(H)1 development in vitro through macrophage production of interleukin-12 (IL-12). Moreover, inhibition of macrophage production of IL-12 may explain the ability of IL-10 to suppress T(H)1 development. Murine immune responses to L. monocytogenes in vivo are of the appropriate T(H)1 phenotype. Therefore, this regulatory pathway may have evolved to enable innate immune cells, through interactions with microbial pathogens, to direct development of specific immunity toward the appropriate T(H) phenotype.