Endocytic Uptake of Particles by Mononuclear Phagocytes and the Penetration of Obligate Intracellular Parasites

As William Trager pointed out some time ago in a review in Science,' all obligate intracellular parasites"be they viral, bacterial, or protozoan "face a common dilemma. That dilemma is to invade their host cells in a way that is not destructive of the host cell upon whose metabolic hospitality and functional well-being their own reproduction depends. Simply stated, these organ isms must penetrate the plasma membranes of their host and take up residence in a suitable location in the cell's cytoplasm. Since many of the speakers in this session will address them selves to the issues of penetration and intracellular location of specific organisms, I view my task as