FURTHER DESCRIPTION OF THE LY-5 SYSTEM

The Ly-5 system of alloantigens was reevaluated with the aid of an Ly-5 congenic mouse strain and an additional serological technique, the PA-SRBC rosette assay, not previously applied to Ly-5. In the PA-SRBC assay, SRBC to which PA (Staphylococcal Protein A) has been coupled react with antibodycoated cells to form rosettes. The PA-SRBC assay was more sensitive than the cytotoxicity assay in detecting Ly-5 on all cell types tested, with the exception of thymocytes, on which Ly-5 was more efficiently demonstrable by the latter test. Thus, the use of both assays gave a more complete picture of the Ly-5 system. Evidently Ly-5 is expressed on most cells of the hematopoietic lineage, but on no other cells so far tested. The Ly-5+ cell population includes all known sets of T cells, prothymocytes, sets of B cells, cells of myeloid and monocyte-macrophage types and natural killer cells. Erythrocytes and proerythroblasts are Ly-5-, but the Ly-5 phenotype of less differentiated erythrocytic cells is uncertain. By means of radiation chimeras, made by restoring lethally irradiated mice with Ly-5 congenic bone marrow, the weakly Ly-5+ phenotype of liver and of kidney was shown to be due to immigrant circulating cells. The Ly-5 phenotypes of tumors conform to this scheme of Ly-5 tissue representation. The Ly-5+ tumors included more than 40 leukemias tested, plasmacytomas, putative transformed equivalents of slg-: Lyb-2+ early B cells, a mastocytoma, a monocytic line, and three lines related to the macrophage. The other tumors tested -a sarcoma, a spontaneous mammary carcinoma, a teratocarcinoma and a neuroblastoma - were Ly-5-. © 1979 Springer-Verlag New York Inc.