Three major areas of study are projected in this research program. a) The molecular mechanisms of cell motility and chemotaxis will be further explored, with particular attention paid to the insertion of new membrane mass into the leading edge of a cell as a critical feature of cell extension. In addition, monoclonal antibodies directed to key cell surface components involved in chemotaxis and cell motility will be sought for. b) The molecular mechanisms involved in capping and related cell surface - cytoskeletal interactions will be investigated, focusing on a monoclonal antibody we have produced that appears to be directed to an integral protein that is associated with actin microfilaments underlying the cell membrane. c) The intracellular events involved in cytoxicity by natural killer cells and cytotoxic T lymphocytes (CTL) will be further explored in a system involving restricted recognition of CTL of target cells infected with lymphocytic choriomeningitis virus (LCMV), with which the nature of cell surface signalling events from the target cell to the effector cell will be explored.