Genetic and biochemical characterization of human lymphocyte cell surface antigens. The A-1A5 and A-3A4 determinants.

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Abstract
The genes that code for the human lymphocyte cell surface determinants defined by monoclonal antibodies A-1A5 and A-3A4 were genetically mapped. All human chromosomes, except Y, were included in a series of human < mouse lymphocyte hybrid populations that retained expression of lymphocytes specific surface markers. Expression of the A-1A5 and A-3A4 antigens was quantitated by indirect immunofluorescence and fluorescence-activated cell sorter (FACS) analysis. Hybrid populations heterogeneous for antigen expression were sorted to yield antigenically homogeneous subpopulations. Isozyme analysis indicated concordant segregation of the A-1A5 determinant with chromosome 10 and the A-3A4 determinant with chromosome 4. In contrast to the unhybridized human parent cell line (MOLT-4), from which A-1A5 immunoprecipitated 2 proteins (160,000 and 125,000 MW), A-1A5 only immunoprecipitated a single band (125,000 MW) from an A-1A5-expressing human < mouse hybrid. The genetic disassociation of these 2 proteins from the A-1A5-reactive complex suggests that the appearance of the 160,000 MW protein requires a gene locus that is unlinked to the locus for the 125,000 MW protein on chromosome 10. A 3rd component of the A-1A5-reactive protein complex (210,000 MW), which is recognized by the monoclonal antibody TS2/7, was not expressed on the parent MOLT-4 cells, but was weakly expressed on MOLT-4 < mouse BW5147 hybrids. This allowed preliminary mapping of that determinant to either chromosome 10 or 15. The A-3A4 antigen (.apprx. 45,000 MW) is a novel cell surface structure expressed on all hematopoeitic cell lines tested, and represents the 1st cell surface marker mapped to chromosome 4.

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