SPECIFIC IMMUNE INDUCTION FOLLOWING DNA-BASED IMMUNIZATION THROUGH IN-VIVO TRANSFECTION AND ACTIVATION OF MACROPHAGES ANTIGEN-PRESENTING CELLS

The initiation of an adaptive immune response requires Ag presentation in combination with the appropriate activation signals. Classically, Ag presentation and immune activation occur in the lymph node and sple en, where a favorable organ architecture and rich cellular help can en hance the process. Recently, several investigators have reported the u se of DNA expression cassettes to elicit cellular and humoral immunity against diverse pathogens, Although the immune mechanisms involved ar e still poorly understood, plasmid inoculation represents a model syst em for studying immune function in response to invading pathogens. In this report, we demonstrate the presence of activated macrophages or d endritic cells in the blood lymphocyte pool and peripheral tissues of animals inoculated with DNA expression cassettes. These cells are dire ctly transfected in vivo, present Ag, and display the surface proteins CD80 and CD86, Our studies indicate that these cells function as APC and can activate naive T lymphocytes, They may represent an important first step APC in genetic immunization and natural infection.