The surface of paramecia, like many other protozoa, is coated with protein antigens which comprise a group of structurally similar molecules. Generally, an individual cell will express only one antigen, although given appropriate environmental stimuli, new antigens from a restricted repertoire can be made to appear. These antigenic shifts apparently are not accompanied by genomic rearrangements. The goal of these studies is to investigate the regulation of expression of these antigens and, in particular, to expand studies on control by the antigens themselves and by inhibitors found in conditioned medium. I propose to: a) isolate regulatory molecules from medium (using gel electrophoresis column chromatography, etc.); b) determine whether these molecules bind to antigens (using enzyme linked immunosorbent assay and other methods); c) assay media (in which paramecia have been cultured) for inhibitors for unexpressed serotypes; and d) determine whether inhibitors that are copurified with an antigen are specific for the antigen. A knowledge of the control of surface protein expression could be useful in several areas of health-related concerns: immunity against and persistence of parasitemias associated with pathogenic protozoa and their variant surface antigens; the relationship of cell induced surface changes to lymphocytes function and to neoplastic processes; and the elucidation of a possible mechanism for regulation of eucaryotic gene expression.
