Genetic analysis of the human cell surface: antigenic marker for the human X chromosome in human-mouse hybrids.

Somatic cell hybrids of human fibroblasts and mouse A9 cells, carrying only a portion of the human X chromosome in a mouse chromosome background, were injected into C3H mice. The resulting mouse anti-hybrid cell antisera contain antibodies found to be human specific and to react with only those hybrid cells carrying the human X chromosome, as confirmed by essentially perfect concordance between antibody binding assayed by indirect immunofluorescence and presence of the human X-linked enzyme hypoxanthine phosphoribosyl-transferase determined by autoradiographic assay of [3H] hypoxanthine utilization. Heterogeneous mixtures of hybrid cells may be analyzed into fluorescent (X plus) and nonfluorescent (X minus) subpopulations and fractionated viably by using a fluorescence-activated cell sorter.