Isolation of a cloned cell line expressing variant H-2Kk using fluorescence-activated cell sorting

We describe here a method for the isolation of somatic cell variants that express a structurally altered gene product on their cell surface. The method makes it possible to select positively for cells of the variant phenotype which is defined by loss of a given antigenic determinant. As an example, we present the isolation of a cloned cell line expressing a structurally altered H-2Kk molecule, designated H-2KkS1. Cells of this phenotype were found to be present in the wild-type population at a frequency of 10(-5)-10(-6) and were isolated in three rounds of selection in the fluorescence-activated cell sorter (FACS) and subsequent growth in vitro.