MODULATION OF PHAGOCYTES BY MONOCLONAL ANTIBODIES

Inflammation is characterized by the rapid accumulation of granulocytes and monocytes at the site of tissue injury. These cells respond to chemotactic factors released by the tissue. The events in chemotaxis include binding of the chemotactic signal to specific cell membrane receptors, transduction of the chemical signal to the motility apparatus of the cell and directed cell movement. In order to further understand the inflammatory response, it is important to characterize mechanisms in this process. By fusing spleen cells from mice immunized with normal human granulocytes or monocytes with myeloma 653 cells, we have produced specific monoclonal antibodies directed against human phagocytes as determined by cytofluorographic analysis. Using the Boyden chamber and under agarose techniques, we have found that 5 of the antibodies are chemotactic or modify granulocyte chemotaxis. Three of these are stimulatory and 2 are inhibitory. Another antibody has also been identified that stimulates monocyte chemotaxis. The overall objective of this proposal is to determine the mechanism by which these antibodies modulate chemotaxis. Preliminary data indicates that the antibodies do not alter the binding of chemotactic factors to their cell surface receptors. Our hypothesis is that the antibodies modify one or more of the proposed chemotactic signal transduction mechanisms. These include: (1) alteration of membrane calcium ion fluxes, (2) activation of lipoxygenase and (3) methylation of cell membrane components. We plan to examine the effects of the antibodies on these processes and to further characterize their interaction with chemotactic factor receptors. Chemotaxis of phagocytes to injured sites is also associated with phagocytosis of tissue debris, lysosomal degranulation and a respiratory burst. We found that one of the chemotactic antibodies, L12.2, stimulates the respiratory burst. We will also examine the effects of the antibodies on phagocytosis and lysosomal degranulation. The availability of monoclonal antibodies that modulate cellular functions provides a unique opportunity to study the regulation of phagocyte activity. The advantage lies in their specificity for a single antigenic site. This will allow us to dissect and elucidate specific cellular and biochemical mechanisms of chemotaxis and to understand the role of this process in inflammation and disease.