Monoclonal antibodies: use to detect developmentally regulated antigens on D. discoideum amebae

We have used monoclonal antibodies to detect developmentally regulated cell surface antigens on D. discoideum amebae. A study of an antigen detected using an antibody produced by a hybridoma line implicates a previously undescribed component in the process of cell aggregation. This antigen (consisting of a doublet of 69,000 and 73,000 molecular weight) is first detected during the early hours of cell starvation and is present until cells begin slug formation. The developmental appearance of the antigen is not controlled by cAMP pulses and is distinct from that of Contact A sites. Fab fragments directed against the antigen are potent inhibitors of aggregation but do not inhibit the differentiation of cells to aggregation competence.