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A unique human cell line designated LAZ 221 has been established from the peripheral blood of a patient with acute lymphocytic leukemia of the "null" cell type. The cell line does not possess the Epstein-Barr virus nuclear antigen and has a karyotype of 45,XX,-9,-12,+(9q12q). Both the established cell line and the patient's uncultured blast cells share the same phenotypic markers. They both lack T-cell markers. They fail to form sheep erythrocyte rosettes and do not react with T-cell-specific antisera (TH1-, HTL-), nor do they possess B-cell markers. They do not form rosettes with erythrocytes sensitized with complement, and they are surface immunoglobulin negative. However, they do possess an HLA-D-related glycoprotein complex of 23,000 to 30,000 daltons, an la-like antigen. Thus, LAZ 221 shares the phenotype of the patient's uncultured blasts and is a cell line representative of about 75% of all human acute lymphocytic leukemias. In this respect it differs from previously described human hematopoietic cell lines.

Two predominant patterns of late X replication were observed in both short-term and established human lymphoid cultures. One pattern was found in a minority of short-term cultured T-cell metaphases, in most lectin-stimulated B cells, and, with minor variations, in established B-cell lines. In these cells, DNA replication terminated in the distal part of the long arm of the late X. A different pattern was found in the majority of lectin-simulated T cells and in the T-cell line CCRF-CEM. These cells exhibited terminal replication in a region of the long arm of the late X that was nearer to the centromere. It is speculated that the variations in replication patterns correlate with phenotypic and functional characteristics of human lymphoid subsets.

The relative amounts of alpha-amd beta-globin mRNA and globin gene DNA were measured in reticulocyte RNA and lymphocyte DNA of an individual with homozygous hereditary persistence of fetal hemoglobin whose red blood cells contain 100% fetal hemoglobin (hb F: alpha2gamma2.) Molecular hybridization assays used as probes full-length DNA copies of human alpha- and beta-globin messenger RNA. The results of these hybridization assays demonstrated the expected amounts of alpha-globin mRNA and gene DNA, but absence of beta-globin mRNA and absence of beta-globin gene DNA. In the individual studied, hereditary persistence of fetal hemoglobin is associated with total deletion of the beta-globin structural gene.