PROPERTIES OF DENDRITIC CELLS AND MACROPHAGES

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The grant will study several cell types that are important in the generation of immune responses: dendritic cells, which are active stimulators of cell-mediated immunity, particularly transplant rejection; macrophages, which are capable of resisting microorganisms and tumors; and helper T lymphocytes, which promote many host defense mechanisms such as antibody formation and killer T cells. The work is divided into 4 subprojects, each in progress and each carried out by specific personnel. The projects require the isolation and characterization of defined murine cell types in culture. A. Skin dendritic cells (Langerhans cells) are immunologically immature, but become active accessory cells in culture. Monoclonal antibodies (MAb) will be raised to immature and mature Langerhans cells to help identify functionally significant, dendritic cell surface molecules, and to localize analogous cells in tissues other than skin. B. Leukocytes will be isolated from the livers of mice that are resisting infection with Listeria. The cells will be used to determine the types of T lymphocytes, antigens, and lymphokines that sustain the microbicidal activities of macrophages derived from an inflammatory site. C. Surface molecules involved in the interaction of dendritic cells and responding lymphocytes will be studied in discrete cell aggregates which form during immune responses in culture. ImmunoEM with MAb will localize specific proteins at dendritic-T cell contact zones. MAb will be tested as blockers of clustering and of function within aggregates. Mediators required for the early stage of T cell activation will be studied with emphasis on factors and bioassays that explain the capacity of dendritic cells to make helper lymphocytes IL-2 responsive. D. The function of helper T lymphocytes will be analyzed with a new model in which the cells are primed to carrier proteins in culture. The relative capacity of helper cells to respond to native vs. degraded proteins will be documented. The different requirements for the growth and differentiation of hapten-specific B lymphocytes will be considered with intact, carrier-specific T cells as helper cells. The function of interleukins and dendritic cells in the development of killer T cells, which like antibody secreting cells require helper lymphocytes, will be studied using unprimed lyt-2 T cells as responders.