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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mitogen-induced blast transformation of peripheral blood lymphocytes and quantitative changes in circulating T- and B-cells were studied serially in cats inoculated with feline leukemia virus (FeLV). Concanavalin A-induced blast transformation sharply declined beginning at 5 weeks post inoculation (Pl) in FeLV-infected cats when compared to age-matched uninfected control cats. Similar but less consistent changes were seen in responses to pokeweed mitogen-induced stimulation. In most infected kittens this defect persisted until they died from thymic lymphosarcoma, 15-24 weeks Pl. An early lymphopenia, due primarily to a decrease in circulating B-cells, occurred in infected cats 5-8 weeks Pl. Following a return of total and B-lymphocytes to control values, infected cats developed increased numbers of T-cells at 16 or more weeks Pl, which correlated with circulating lymphoblastic lymphocytes bearing T-cell markers. These results correlated neoplasia arising in a thymus-derived lymphocyte population with mitogenic hyporeactivity in the preneoplastic period and suggested that FeLV-induced immune alterations may be a necessary antecedent of leukemogenesis in the cat.
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PMID:Lymphocyte mitogen reactivity and enumeration of circulating B- and T-cells during feline leukemia virus infection in the cat. 18 90

We recently reported that thymocytes from 6-month-old preleukemic AKR mice express higher levels of murine leukemia virus (MuLV)-related antigens that thymocytes from 2-month-old mice. We have now found that the level of xenotropic MuLV (defined operationally as MuLV able to infect mink cell cultures) is also markedly increased in thymus of 6-month-old AKR mice and that this increase in virus correlates closely with increased MuLV-antigen expression. There is no increase of MuLV antigen or xenotropic virus in spleen or lymph nodes. Production of ecotropic MuLV remains unchanged with age in thymus, lymph nodes, and spleen. Thymic grafts from 6-month-old AKR mice, but not from 2-month-old mice, induce both amplified MuLV-antigen expression and xenotropic virus production in the thymus of young AKR recipients. Experiments with lethally irradiated AKR mice reconstituted with syngeneic bone marrow cells indicate that age-related changes in the thymus rather than in bone marrow precursor cells are responsible for MuLV-antigen amplification.
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PMID:Changes in expression of murine leukemia virus antigens and production of xenotropic virus in the late preleukemic period in AKR mice. 18 51

Most X-irradiation-induced thymomas in C57BL/6 mice are virus-free when assayed by immunofluorescence for the gs antigen (gsa) of murine leukemia virus (MuLV). Virus was induced transiently in bone marrow cells and later appeared in thymus cells. Six to 7 weeks post irradiation, thymocytes and bone marrow cells were MuLV gsa-negative and remained negative for the lifetime of most animals, whether or not they contracted overt leukemia. During the period when MuLV gsa-positive bone marrow cells were found, XC-positive syncytia-producing bone marrow cells were also found. Virus information was expressed, therefore, for a limited duration, long before any signs of leukemia in the animals were evident. MuLV gsa-positive thymocytes taken from mice 4 weeks after X-irradiation were cocultivated with a series of indicator cells. B-tropic virus, in addition to a xenotropic virus, was isolated from these cells. Ecotropic virus was not found in normal mouse thymocytes, in irradiated thymocytes a few days after termination of the X-irradiation sequence, or in most primary thymomas. All thymocytes produced only xenotropic virus in the cocultivation assays. Expression of the ecotropic virus was, therefore, transient, as assayed by immunofluorescence, XC syncytia formation, and virus isolation from MuLV gsa-positive thymus cells.
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PMID:Transient virus expression during murine leukemia induction by X-irradiation. 18 45

334C murine leukemia virus, which induces a high incidence of lymphatic leukemias (80-90%) in susceptible mice following a long latency period, was found to cause a severe in vivo suppression of direct plaque-forming cells from the spleen, following antigenic stimulation with sheep red blood cells. Neonatally infected inbred BALB/c and outbred Ha/ICR Swiss mice, which develop a sustained viremia, were highly susceptible to the immunosuppressive effect of this virus as early as 1 week after virus infection, long before any detectable histologic evidence of leukemia development. Ha/ICR Swiss mice, which are highly resistant to the leukemogenic potential of this virus following infection in adult life, were highly resistant to its immunosuppressive action; only a moderate and transient suppression, without viremia, occurred 2 weeks after virus infection. In marked contrast, BALB/c mice were highly susceptible to the immunosuppressive action of 334C murine leukemia virus following infection in adult life; a severe and sustained suppression was observed as early as 1 week after virus infection and was followed by a sustained viremia, beginning at 2 weeks, with a 55-60% incidence of leukemia observed over a period of 1 year. Infectious virus was essential to produce theimmunosuppressive effect; heat-inactivated (56 degrees C/30 min) and attenuated (4 degrees C/4 1/2 mo) virus preparations were ineffective. The plaque-forming response of spleen cells from lethally irradiated syngeneic adult BALB/c mice was markedly suppressed following reconstitution with thymus-dependent (T) or thymus-independent (B) cells from the thymus and bone marrow, respectively, of virus-infected mice, in combination with each other, or with the appropriate cell populations from normal mice.
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PMID:Immunosuppression in mice after inoculation with 334C, a murine lymphatic leukemia-inducing virus. 19 Apr 12

The major core protein, p30, of mouse C-type viruses was quantitated radioimmunologically in lymphoid organs and blood from inbred strains of mice. The concentration of p30 in thymus and spleen had a weak and moderate correlation, respectively, to leukemia frequency. In contrast, the concentration of p30 in blood from mice with a high incidence of leukemia (strains AKR and C58) was 100-fold increased at 2 months of age compared with 10 strains with a low incidence of the disease. The SJL mice, which have a high incidence of reticulum cell neoplasms, showed generally elevated, but variable, values. The high concentration in AKR blood developed during the first weeks of life. Approximately one-third of the DBA/2 mice had elevated levels after 4 to 5 months, whereas the values from mice of the 129 strain were low irrespective in their age. The major part of p30 appeared to be associated with the erythrocytes. The concentration of p30 in the blood seems to reflect the presence of replicating virus in mice. It identifies among the inbred strains a high leukemia group one-half year prior to disease.
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PMID:C-type virus protein p30 in blood from inbred mice correlates with their later incidence of leukemia. 19 98

A new type of murine leukemia virus has been detected in thymuses of leukemic and late preleukemic AKR mice, in lymphomas developing in NIH Swiss mice carrying the AKR ectopic virus-inducing loci Akv-I or Akv-2, and in the thymus of a preleukemic C58 mouse. The viruses induce focal areas of morphologic alteration in a mink lung cell line and are tentatively referred to as "mink cell focus-inducing" (MCF) strains. They have the host range of both xenotropic and N-tropic ecotropic murine leukemia viruses, are neutralized by antisera to both ecotropic and xenotropic viruses, and are interfered with by both viruses. They may represent a particular type of genetic recombinant which emerges during the preleukemic period in high-ecotropic-virus mouse strains, and they may play a significant role in the etiology of spontaneous lymphomas.
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PMID:A new class of murine leukemia virus associated with development of spontaneous lymphomas. 19 26

The role of the thymus in induction of leukemia was studied in vitro. Curltivation of normal thymus cells on thymus epithelial reticulum cell monolayers that had been grown from radiation leukemia virus-induced leukemic thymuses rendered the thymocytes leukemic. C57BL/6 thymocytes were cultivated for 3 days on leukemic thymus reticulum monolayers, and 106 thymocytes were injected i.p. into young adult C57BL/6 mice. After 3 to 4 weeks all mice died of disseminated lymphatic leukemia. Mice given thymocytes that had been cultivated on thymus epithelial reticulum monolayers from normal mice did not develop lymphomas. The leukemic thymus epithelial reticulum cells were shown to produce thymotropic as well as ecotropic and xenotropic radiation leukemia virus. (Thymotropic virus has affinity for thymus lymphocytes but noes not infect fibroblasts.) The cells were brightly positive for murine leukemia virus group-specific antigen in immunofluorescence tests. Leukemic thymus epithelial reticulum cells produced ample infectious exotropic virus in the culture supernatant, although the cells were negative in the XC syncytia test. Upon infection of mouse fibroblasts with ecotropic virus produced by the leukemic reticulum cells, XC syncytia were readily obtained. Thymocytes that were cultivated on leukemic thymus reticulum cells became positive for murine leukemia virus group-specific antigen and produced syncytia in the XC test. Thus, in vitro lymphomagenesis of the thymocytes that were cultured on leukemic thymus reticulum cells was associated with their infection with thymotropic and ecotropic radiation leukemia virus.
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PMID:Leukemogenesis in vitro induced by thymus epithelial reticulum cells transmitting murine leukemia viruses. 19 63

The synthesis and processing of feline leukemia virus (FeLV) polypeptides were studied in a chronically infected feline thymus tumor cell line, F-422, which produces the Rickard strain of FeLV. Immune precipitation with antiserum to FeLV p30 and subsequent sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used to isolate intracellular FeLV p30 and possible precursor polypeptides. SDS-PAGE of immune precipitates from cells pulse-labeled for 2.5 min with [35S]methionin revealed the presence of a 60,000-dalton precursor polypeptide (Pp60) as well as a 30,000-dalton polypeptide. When cells were grown in the presence of the proline analogue L-azetidine-2-carboxylic acid, a 70,000-dalton precursor polypeptide (Pp70) was found in addition to Pp60 after a 2.5-min pulse. The cleavage of Pp60 could be partially inhibited by the general protease inhibitor phenyl methyl sulfonyl fluoride (PMSF). This partial inhibition was found to occur only if PMSF was present during pulse-labeling. Intracellular Pp70 and Pp60 and FeLV virion p70, p30, p15, p11, and p10 were subjected to tryptic peptide analysis. The results of this tryptic peptide analysis demonstrated that intracellular Pp70 and virion p70 were identical and that both contained the tryptic peptides of FeLV p30, p15, p11, and p10. Pp60 contained the tryptic peptides of FeLV P30, P15, and P10, but lacked the tryptic peptides of P11. The results of pactamycin gene ordering experiments indicated that the small structural proteins of FeLV are ordered p11-p15-p10-p30. The data indicate that the small structural proteins of FeLV are synthesized as part of a 70,000-dalton precursor. A cleavage scheme for the generation of FeLV p70, p30, p15, p11, and p10 from precursor polypeptides is proposed.
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PMID:Analysis of intracellular feline leukemia virus proteins II. Generation of feline leukemia virus structural proteins from precursor polypeptides. 19 17

Anomalous appearance of TL (thymus-leukemia) antigens is a characteristic feature of radiation-induced leukemias of C57bl/6 mice. We now report that thymocytes of irradiated C57BL/6 mice express TL antigens long before the development of overt leukemia. Thus, TL is a marker for preleukemic changes occurring during radiation leukemogenesis. Low levels of murine leukemia virus (MuLV)-related antigens are also detected on preleukemic thymocytes. Comparative tests on individual mice show no direct correlation between TL and MuLV antigen expression.
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PMID:Preleukemic expression of TL antigens in x-irradiated C57BL/6 mice. 19 1

By competition radioimmune assays with antisera against AKR murine leukemia virus (MuLV) gp 71 or antisera against xenotropic virus, and iodinated AKR MuLV gp71 or BALB(X) gp71, antigens serologically indistinguishable from the viral antigens can be detected in tissues of normal mice in the absence of overt virus expression. An antigen serologically indistinguishable from AKR MuLV gp71 can be readily detected in normal bone marrow cells of the common strains of mice including NIH Swiss, 129/J, and SWR/J, as well as in Mus cervicolor and Mus musculus casteneus. In contrast, this antigen is not detected in normal spleen, thymus, lymph nodes, or serum. Similarly, an antigen serologically indistinguishable from BALB(X) gp71 was found in all normal mouse sera examined. This antigen was not present in fetal liver, perfused adult liver, thymus, spleen, lymph nodes, or bone marrow of the mice examined. An equivalent antigen was detected in sera from Mus musculus casteneus but not in sera from Mus cervicolor.
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PMID:Expression of AKR murine leukemia virus gp71-like and BALB(X) gp-71-like antigens in normal mouse tissues in the absence of overt virus expression. 19 2


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