Distribution of the 124-kd antigen defined by monoclonal antibody AML-1-99 on normal and leukemic myeloid cells.

We have produced a monoclonal antibody (MoAb), AML-1-99, that defines a novel 124-kd protein antigen expressed on a subpopulation of monocytes and on the majority of hematopoietic progenitor cells of the granulocyte-monocyte (CFU-GM), erythroid, and mixed-lineage classes. AML-1-99 is lytic to bone marrow (BM)- and peripheral blood-derived progenitor cells in the presence of rabbit complement (C'). AML-1-99 is not toxic to progenitor cells in the absence of C', nor does it modify their growth when included in colony-forming cultures. Several leukemia cell lines, including HL-60, U937, KG-1a, and Daudi cells, express the antigen on the majority of cells. Freshly isolated leukemia cells from patients with acute myelogenous leukemia (AML) react variably with AML-1-99. Leukemia colony-forming cells from several AML patients express the antigen and could be eliminated by treatment with AML-1-99 and C'. Cell sorting and immune rosette techniques were successfully applied to normal BM and chronic myelocytic leukemia cell populations using AML-1-99 with the result that significant enrichment of CFU-GM could be accomplished. The pattern of reactivity of this MoAb and its apparent molecular weight suggests that AML-1-99 recognizes a newly defined myeloid-associated cell surface antigen.

A new form of Niemann-Pick disease characterised by temperature-labile sphingomyelinase.

A new type (F) of Niemann-Pick disease characterised by childhood onset of splenomegaly, lack of neurological involvement, and diminished sphingomyelinase activity is described. The clinical presentation and heat-labile sphingomyelinase activity of this type F Niemann-Pick disease distinguishes it from other types of Niemann-Pick disease.

The isolation and characterization of sphingomyelinase from human placental tissue.

Human placental sphingomyelinase activity was eluted as a single symmetrical peak from Sephadex G-200 with a molecular weight of 290000; however, the enzyme behaved heterogeneously on ion exchange chromatography. A specific species of sphingomyelinase was purified approx. 10 000-fold to a constant specific activity of 274 000 nanomol of sphingomyelin hydrolyzed per mg protein per h. When the purified enzyme was examined on sodium dodecyl sulfate disc gel electrophoresis, two distinct protein bands in approximately equal proportions with molecular weights of 36 800 and 28 300 were found. The specificity of the enzyme is directed towards both the hydrophilic phosphocholine and the hydrophobic ceramide moieties of sphingomyelin. Possible interrelationships between the heterogenous forms of placental sphingomyelinases are discussed.

A practical chromogenic procedure for the detection of homozygotes and heterozygous carriers of Niemann-Pick disease.

Niemann-Pick disease is caused by a deficiency of sphingomyelinase in organs and tissues. Determinations of sphingomyelinase activity had required the use of sphingomyelin labeled with radiocarbon or radiohydrogen. These materials are expensive, and their use is restricted to laboratories with radioactive counting facilities. An analogue of sphingomyelin, 2-hexadecanoylamino-4-nitrophenylphosphorylcholine, was synthesized. This substance is hydrolyzed by highly purified sphingomyelinase, and by sphingomyelinease in extracts of human liver tissue, cultured skin fibroblasts, cultured amniotic cells and washed leukocyte preparations. Extracts of tissues and cells from patients with Niemann-Pick disease Type A do not hydrolyze this compound, whereas heterozygotes and patients with Niemann-Pick disease Type C have an intermediate level of hydrolytic activity. Thus, the analogue is a reliable chromogenic reagent for the diagnosis of patients with Niemann-Pick disease and the detection of heterozygous carriers of the Niemann-Pick trait.