Approximately 10% of newborn infants with Down Syndrome develop a form of megakaryoblastic leukemia which usually disappears spontaneously during the first months of life. The evidence that this "Transient Leukemia" is truly leukemia includes the following: it is clonal proliferation, it can be fatal and tissue infiltration of leukemic cells occurs. Also in approximately 25% of cases that recover, Acute Megakaryoblastic Leukemia will develop in the first four years of life, which, if not treated, is fatal. Evidence regarding the megakaryoblastic nature of the leukemic cells is presented as well as a description of the lethal forms of the disease. The study of Transient Leukemia is of considerable importance because it can provide insight into both the nature of leukemia and its relation to trisomy 21.

Dermal microvascular endothelial cells (DMEC) exposed to hypoxic conditions show a rapid induction of several proteins that do not increase in other cell types placed in a similar environment. These DMEC proteins differ from the well-characterized stress proteins that have been observed in a wide variety of cultured cell types. The DMEC proteins are induced rapidly, within 2–4 h, and are expressed transiently. They include a group of acidic proteins (pI ∼ 5–5.2) with molecular weights in the range 100 000–120 000 and at least one glycoprotein (pI 5.1, Mr 57 000) that is probably expressed on the cell surface. In some primary DMEC cell strains, this response is accompanied by a transient overall increase in protein synthesis. The oxygen-regulated proteins (ORP) that are induced in most other cell types under hypoxic conditions show little variation in their rate of synthesis in DMEC within the first 24 h. The response of DMEC differs from that of umbilical vein endothelial cells (UVEC) and from spindle-shaped cells derived from DMEC, that show a response to hypoxia that is similar to most other cell types. The changes seen in DMEC proteins take place in the same time scale as ischemia-reperfusion injury and may reflect the specialized change of functions of the microvasculature observed under conditions of hypoxic stress in vivo.

The electronic structure of the transition state for the cyclopropylidene to allene conversion has been probed. The methodology involved the relative rates of ring opening vs trapping by MeOH for a series of variously substituted 2,3-diarylcyclopropylidenes. With the assumption that the rate of trapping was unaffected by substituents, a Hammett correlation was constructed. The negative value (-0.72) for rho indicated that the carbenic center attracts electron density in the ring-opening transition state, much like the cyclopropyl cation to allyl cation transition state. Temperature-dependent studies showed that the observed preference for ring opening was driven by entropy factors. Also, using reasonable estimates for the close to diffusion-controlled trapping activation enthalpies, the derived enthalpies for ring opening were in close agreement with the best theoretical values.

Howes, Anthony E. M.D., Ph.D.; Coleman, C. Norman M.D.; Phillips, Theodore L. M.D.; Sutherland, Robert M.D. Author Information

The Adam Smith Problem - Richard F. TeichgraeberIII : ‘Free Trade’ and Moral Philosophy: Rethinking the Sources of Adam Smith's Wealth of Nations. (Durham: Duke University Press, 1986. Pp. xviii, 169. $35.00.) - Volume 49 Issue 3

Hybrids formed between human acute lymphoblastic leukemia (ALL) cells and mouse myeloma have been used to determine the chromosomal location of genes required for the expression of several monoclonal antibody (mAb)‐defined cell surface antigens on ALL cells. Cloned hybrids were tested for antibody binding, immunoprecipitation of the relevant protein, chromosome isoenzyme markers and karyotype. Two antigens of those studied could be definitively mapped, OKT10/p45 to chromosome 4 and BA‐2/p24 to chromosome 12. mAb BA‐2 reacts with the same protein as another mAb designated 609‐29 (anti‐teratocarcinoma). Reactivity with the latter mAb has been previously shown to segregate with chromosome 12.

Human transferrin receptors detected by monoclonal antibody OKT9 appear to be well expressed on cell types known to provide sensitive targets for natural killer (NK) cells. The possibility that transferrin receptors are recognized by NK effector cells has been investigated by three series of experiments: (i) analysis of the correlation between sensitivity to natural killing and the proportion of transferrin receptor-positive cells in different cell lines, (ii) study of the relationship between levels of transferrin receptor expression in cell lines and their capacity to competitively inhibit recognition and killing of the target cell K562 by NK cells, and (iii) comparison of affinity-purified soluble proteolytic fragments of the transferrin receptor and HLA-A, -B molecules for their ability to inhibit the natural killing effect. The data indicate that the transferrin receptor can provide a "target" structure for NK cells. Because transferrin receptors are ubiquitously expressed on normal and malignant proliferating cells, these observations have interesting implications for the possible function of NK cells in vivo.

The monoclonal antibody OKT-9 has been shown to recognize the human transferrin receptor. We have exploited the species specificity of OKT-9 to map a gene controlling human transferrin receptor expression to chromosome 3, using human-mouse somatic cell hybrids. The gene for the human transferrin receptor and the gene controlling transferrin expression may be linked in humans.

The monoclonal antibody OKT9 reacts specifically with the receptors for transferrin on human cells (Sutherland, D. R., Delia, D., Schneider, C., Newman, R. A., Kemshead, J., and Greaves, M. F. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 4515-4519; in Leukemia Markers (Knapp, W., ed) pp. 157-160, Academic Press, New York) and has been used to isolate and characterize this receptor. The receptor is a dimeric glycoprotein (Mr = 180,000) composed of two subunits (Mr = 90,000) and has a pI of approximately 5.2. The transferrin receptor appears to be a transmembrane molecule and is phosphorylated, the phosphate group being predominantly on serine residues. The cell surface form of the molecular possesses both complex and high mannose oligosaccharide chains, which do not appear to have a direct role in antibody (OKT9) binding. The molecule can be cleaved into a Mr = 70,000 fragment from the cell surface, suggesting that the major part of the receptor is exposed to the extracellular environment. The released Mr = 70,000 fragments are not disulfide-linked and possess the antibody (OKT9)- and transferrin-binding sites. Cross-linking studies using radiolabeled transferrin suggest that two molecules of transferrin are bound to each Mr = 180,000 receptor dimer.

A library of monoclonal antibodies plus "conventional' markers (e.g. anti-TdT) have been used to explore the detailed phenotypes of leukaemic cells in relation to normal haemopoietic differentiation. This analysis reveals that consistent, composite phenotypes of different subclasses of lymphoid malignancies closely mimic those of corresponding normal cells at equivalent levels of maturation. It is suggested that three major target cell populations are available for lymphoid malignancy: the pluripotential stem cell (e.g. "lymphoid' blast crisis of CGL), lymphoid progenitors or stem cells in the bone marrow (non-T ALL) or thymus (T-ALL, T-NHL) and long lived, mature and immunocompetent T and B cells (T-CLL, PLL, Sézary and B-CLL, lymphoma respectively). The major phenotypes documented in different leukaemias represent the level of "maturation arrest' imposed on the dominant subclone; this is determined by, but not necessarily synonymous with, the "target cell' and associated clonogenic cell population in the leukaemia. No consistent major abnormalities of gene expression are revealed by this investigation and although they may exist (e.g. loss or acquisition of antigens with malignant progression) we suggest that they are irrelevant to the central issue of what alterations are essential and sufficient for the evolution of clonogenic leukaemic cells. We propose instead that subtle changes, which uncouple proliferation and differentiation, are all that is required.

The acute lymphoblastic leukemia- (ALL) associated membrane antigen is a single glycosylated polypeptide of approximate m.w. of 100,000 (gp100), containing no intrachain disulfide linkages. Approximately 50% of gp100 will bind to lentil lectin, whereas 100% will bind to the lectin from Ricinus communis. Both lentil-binding and lentil nonbinding forms of the antigen appear to be identical by 2-dimensional isoelectric focusing/SDS polyacrylamide gel electrophoresis and peptide mapping. Carbohydrate, although contributing approximately 20 to 25% of the m.w., appears not to be involved in the antigenic site of the ALL antigen as judged by precipitation of a molecule after tunicamycin treatment of cells or glycosidase digestion. Charge shift electrophoresis and labeling with the lipophilic nitrene reagent hexanoyl diiodo-N-(4-azido-2-nitrophenyl)-tyramine suggests that the cALL antigen is probably not an integral membrane protein; however, it remains tightly bound to the plasma membrane after subcellular fractionation. A glycoprotein of the same m.w. has been detected by immunoprecipitation on bone marrow cells of nonleukemic patients. serologic studies indicate that the cALL-associated antigen is found on the terminal transferase-positive lymphoid cells, and it therefore seems likely that the gp100 molecule is a normal gene products of lymphocyte precursors.

Monoclonal antibodies OKT1,3,4,6,8,9,10,11 and 11A have been screened by immunofluorescence (FACS and microscopy) and 125I-binding assays for their cellular specificity in human leukaemia in relation to other cell markers (e.g. cALL gp100 antigen, HLA-DR, TdT, E rosettes). In a series of 69 T cell malignancies a distinctive correlation was observed between phenotype and clinical diagnosis. In every instance, T-ALL cells have an immature or early thymic phenotype and T non-Hodgkin lymphoma have a predominant cortical thymic phenotype indicating that these two malignancies originate from T cell precursors. In contrast, adult T-Sezary leukaemia, T-CLL and T-PLL have mature T cell subset phenotypes, the majority being T3+ T4+ T8− /TdT− “helper/inducer” cell types and are presumed to originate in mature immunocompetent T cells. OKT11 and OKT11A give concordant reactions with E (sheep) rosettes and appear to react with the same receptor structure. The composite phenotype of several T-ALL cell lines can be modulated in vitro by phorbol ester (TPA). HPB-ALL, for example, loses TdT and OKT4 binding, decreases OKT9, maintains OKT8 and increases OKT1, HLA-ABC and OKT11 binding and E rosettes.

The Fusion Materials Irradiation Test (FMIT) accelerator requires 13 RF amplifiers at 80 MHz, with a CW output of 600 kW each. The EIMAC 8973 (formerly the X-2170) was chosen as the amplifier tube for this application. Never before had the 8973 been operated at this power level and frequency; therefore a test program was initiated to determine its capabilities. The tube was operated Class B in the grounded-grid, grounded-screen configuration. Maximum CW output power was in excess of 1 MW, with a plate efficiency greater than 60% and a 14-dB gain. Details of the test setup and the results will be presented.

A library of monoclonal antibodies which show selective reactivity with particular cells or gene products (e.g. HLA-DR, glycophorin) of different cell lineages in the haemopoietic system has been compiled. Using these probes in conjunction with the fluorescence-activated cell sorter (FACS) the pattern and sequence of cell surface antigenic expression on haemopoietic progenitor cells have been mapped. A cell is identified in bone marrow which has a unique membrane phenotype and the nuclear enzyme terminal deoxynucleotidyl transferase. Its composite phenotype is identical to that seen in the common variant of acute lymphoblastic leukaemia (ALL). It is suggested that this cell is a putative B lineage progenitor which provides the major target for ALL. Detailed analysis of erythroid differentiation with monoclonal antibodies on the FACS reveals an intriguing pattern of antigenic expression in which HLA-DR, glycophorin and band III appear in sequence. HLA-DR (Ia-like antigen) may be present on all or most committed haemopoietic progenitor cells and could play an important role in cell interactions regulating early haemopoiesis.

A murine monoclonal antibody (OKT9) raised against human leukemic cells binds to a wide variety of leukemia and tumor cell lines and to a minority of leukemia cells taken directly from patients. Fetal thymus and liver are strongly reactive as are some normal, immature hemopoietic cells and activated lymphocytes. Reactivity with OKT9 appears to correlate with proliferation status in both normal and malignant populations. Biochemical analysis indicates that this structure is a approximately equal to 180,000-dalton glycoprotein with two disulfide-bonded subunits of approximately equal to 90,000-daltons. Isolation of the transferrin receptor from a T-cell line (MOLT-4) indicates that it also has a dimeric approximately equal to 180,000-dalton structure. Radio-labeled transferrin bound to its receptors can be specifically precipitated by the monoclonal OKT9, although the latter does not bind transferrin itself, indicating that the antigenic structure defined by this antibody is likely to be the transferrin receptor.

Cytotoxicity of the radiation sensitizer, Ro-07-0582, in multicell spheroids was potentiated by hyperthermia. Spheroids were treated for different times with and without 1.5 mM Ro-070582 at 37°, 42° and 43°C. The time required for the drug to produce similar levels of cytotoxicity was lowered from about 3 days at 37 °C to 90 min at 41°C. The number of clonogenic cells per spheroid decreased by 50 per cent, compared with heat alone, when Ro-07-0582 was combined with hyperthermia at 42° and 43°C for 1 and 0.5 hr respectively. This combination of modalities achieved the same level of cytotoxicity after 90 min at 42°C compared with 70 min at 43°C. There was a plateau in the cell survival curve at 42°C in the presence of Ro-07-0582 after heat treatments longer than 90 min, suggesting some selection for cells within the spheroids which are particularly sensitive to the combined treatment. These encouraging results suggest the need for further evaluation of these combined modalities in vivo to determine normal tissue toxicity and therapeutic effectiveness.