Human T-cell Leukemia Virus Type I Proviral DNA Research Articles

Secretion of the Human T Cell Leukemia Virus Type I Transactivator Protein Tax

Human T cell leukemia virus type I (HTLV-I) is the etiologic agent of adult T cell leukemia and HTLV-I-associated myelopathy/tropical spastic paraparesis. The HTLV-I protein Tax is well known as a transcriptional transactivator and inducer of cellular transformation. However, it is also known that extracellular Tax induces the production and release of cytokines, such as tumor necrosis factor-alpha and interleukin-6, which have adverse effects on cells of the central nervous system. The cellular process by which Tax exits the cell into the extracellular environment is currently unknown. In most cell types, Tax has been shown to localize primarily to the nucleus. However, Tax has also been found to accumulate in the cytoplasm. The results contained herein begin to characterize the process of Tax secretion from the cell. Specifically, cytoplasmic Tax was demonstrated to localize to organelles associated with the cellular secretory process including the endoplasmic reticulum and Golgi complex. Additionally, it was demonstrated that full-length Tax was secreted from both baby hamster kidney cells and a human kidney tumor cell line, suggesting that Tax enters the secretory pathway in a leaderless manner. Tax secretion was partially inhibited by brefeldin A, suggesting that Tax migrated from the endoplasmic reticulum to the Golgi complex. In addition, combined treatment of Tax-transfected BHK-21 cells with phorbol myristate acetate and ionomycin resulted in a small increase in the amount of Tax secreted, suggesting that a fraction of cytoplasmic Tax was present in the regulated secretory pathway. These studies begin to provide a link between Tax localization to the cytoplasm, the detection of Tax in the extracellular environment, its possible role as an extracellular effector molecule, and a potential role in neurodegenerative disease associated with HTLV-I infection.

Activation of HTLV-I gene transcription by protein tyrosine phosphatase inhibitors

Human T-cell leukemia virus type I (HTLV-I) transcription generally depends on the ability of the viral Tax protein to bind the CREB transcription factor and form an active complex by recruiting CBP/p300 coactivators to the long terminal repeat (LTR). Studies have demonstrated that T-cell activating agents that stimulate CREB are potent inducers of HTLV-I transcription. Herein, we demonstrate that bpV[pic], a protein tyrosine phosphatase (PTP) inhibitor activates the HTLV-I LTR in the presence and absence of Tax expression. Optimal activation occurred at 8 h and was synergistic with forskolin or PGE 2. Infected cell lines and cells transfected with HTLV-I proviral DNA were equally responsive to the synergistic effect of bpV and forskolin on HTLV-I gene expression. Activation of the LTR by bpV[pic] was T-cell receptor-independent, but required ZAP70, calcineurin activity and functional calcium entry. Inhibition of the SHP-1 PTP was suggested to be important. Transfection experiments with a CREB dominant-negative mutant and with isolated TRE1- or CREB-responsive reporter constructs and treatment with the MDL-12,330A adenylate cyclase inhibitor all supported the involvement of a CREB/ATF family member in this bpV-dependent activation of the HTLV-I LTR, although CREB itself did not seem to be involved. Analysis of HTLV-I reporter constructs containing mutated CREB-binding sites also implied the involvement of another element in this activation. These results demonstrate for the first time a powerful effect of PTP inhibitors on HTLV-I LTR activity and suggest participation of both CREB-dependent and -independent pathways in this activation.

Construction of a full-length human T cell leukemia virus type I genome from MT-2 cells containing multiple defective proviruses using overlapping polymerase chain reaction

Human T cell leukemia virus type I (HTLV-I), the etiological agent of adult T cell leukemia, integrates into the host genome as a provirus. Multiple defective copies of the integrated provirus are often present in the host genome. For this reason it is difficult to clone the intact provirus from HTLV-I-infected cells using conventional techniques. Here, we used overlapping polymerase chain reaction (PCR) to construct a full-length provirus of HTLV-I directly from an HTLV-I-transformed cell line, MT-2, which contains multiple defective proviruses. First, four overlapping proviral HTLV-I fragments (1.4–3.9 kb each) were constructed from genomic MT-2 DNA using PCR. Next, the complete HTLV-I proviral DNA (9 kb) was generated from these fragments using asymmetric PCR and cloned into a plasmid vector. 293T cells transfected with this plasmid produced virus-like particles, and we show that these particles are capable of infecting a human T cell line. We propose that this cloning technique constitutes a powerful tool for constructing infectious molecular clones from cells of patients infected with HTLV-I or other viruses.

Construction of a full-length human T cell leukemia virus type I genome from MT-2 cells containing multiple defective proviruses using overlapping polymerase chain reaction

Human T cell leukemia virus type I (HTLV-I), the etiological agent of adult T cell leukemia, integrates into the host genome as a provirus. Multiple defective copies of the integrated provirus are often present in the host genome. For this reason it is difficult to clone the intact provirus from HTLV-I-infected cells using conventional techniques. Here, we used overlapping polymerase chain reaction (PCR) to construct a full-length provirus of HTLV-I directly from an HTLV-I-transformed cell line, MT-2, which contains multiple defective proviruses. First, four overlapping proviral HTLV-I fragments (1.4–3.9 kb each) were constructed from genomic MT-2 DNA using PCR. Next, the complete HTLV-I proviral DNA (9 kb) was generated from these fragments using asymmetric PCR and cloned into a plasmid vector. 293T cells transfected with this plasmid produced virus-like particles, and we show that these particles are capable of infecting a human T cell line. We propose that this cloning technique constitutes a powerful tool for constructing infectious molecular clones from cells of patients infected with HTLV-I or other viruses.

Granular lymphocytic leukemia derived from γδ T-cell expressing cytotoxic molecules

We here present an extremely rare case of granular lymphocytic leukemia derived from γδ T-cell (γδ T-GLL). The blood picture at diagnosis was as follows; white cell count 25.7×10 9/l containing 94% atypical lymphocytes with cytoplasmic granules, hemoglobin 11.8 g/dl and platelet count 124×10 9/l. The atypical lymphocytes were positive for CD2, CD3, CD5, CD7, CD56 and TCR γδ, but negative for CD4, CD8, CD57, TCR αβ and B-cell antigens. The cytotoxic molecules, T-cell intracellular antigen-1 (TIA-1) and granzyme B, were positive by immunocytochemical analysis. Southern blot analysis showed rearrangement of T-cell receptor Jγ and Cβ genes but germline configuration of the JH gene. Neither serum antibody against human T-cell leukemia virus type-I (HTLV-I) nor the integration of HTLV-I proviral DNA was detected. CT scan showed splenomegaly but no lymph node enlargement. A diagnosis of γδ T-GLL was made, and she has been followed up without any therapies for more than 4 years.

IL-2 independent transformation of a unique human T cell line, TY8-3, and its subclones by HTLV-I and -II.

Human T cell leukemia virus type I (HTLV-I) is etiologically associated with adult T cell leukemia (ATL) and chronic neurological disease, tropical spastic paraparesis (TSP). In our study, a unique IL-2 dependent human T cell line, designated TY8-3, was established from a thymoma obtained from a myasthenia gravis patient. The cells were heterogeneous and mainly consisted of those with CD4 , CD8 as well as activation markers and adhesion molecules including IL-2Ralpha,beta,gamma, CD45RO, Tf-R, HLA-DR, LFA-1alpha,beta, LFA-3, ICAM-1 and OX40 but without CD3 surface markers. Furthermore, these cells underwent an efficient and reproducible IL-2 independent transformation upon cocultivation with HTLV-I/II producing cell lines. Interestingly, although the infected cells became IL-2 independent, the growth rate of infected cells was significantly lower than those of parental TY8-3 cells. Clonal HTLV-I proviral DNA and viral particles were detected in the cells. Down-regulation of the lck and fyn genes and activation of the lyn gene was demonstrated in the IL-2 independent HTLV-positive TY8-3 cells. Subclones of TY8-3 cells were again able to be efficiently transformed and became IL-2 independent several months after coculture. Our results thus exhibit that TY8-3 cells and its subclones provide us with a very unique model whereby IL-2 independent transformation events of human T cells by HTLV-I/II in vitro can be studied at a clonal level.

Human T cell leukemia virus type I expression in salivary glands of infected patients.

Human T cell leukemia virus type I (HTLV-I) sequences were sought in labial salivary glands of patients with HTLV-I-associated myelopathy or tropical spastic paraparesis and of seropositive neurologically healthy carriers. HTLV-I proviral DNA was found by polymerase chain reaction amplification in DNA extracted from lip biopsies of every patient. Viral RNA was found by in situ hybridization in the acini epithelium, as well as in lymphocytic infiltrates. This observation suggests that HTLV-I expression in labial salivary glands could participate in the inflammatory lesions observed in these patients. Some seronegative patients with Sjögren's syndrome or dryness syndrome were also positive for viral transactivator tax DNA (41% in Martinique and 16% in non-HTLV-I-endemic region). Despite histologic signs of lymphocytic infiltration, no viral expression was found in the labial salivary glands of these patients.

Increased expression of interleukin-2 receptor alpha on peripheral blood mononuclear cells in HTLV-I tax/rex mRNA-positive asymptomatic carriers.

Using the double-nested reverse transcription-polymerase chain reaction, we assayed human T-cell leukemia virus type I (HTLV-I) tax/rex-encoded mRNA in the peripheral blood mononuclear cells (PBMCs) of asymptomatic carriers as an index of the expression of HTLV-I in vivo in relation to the proviral DNA level. HTLV-I tax/rex mRNA was detected in only 1 (3.3%) of 30 samples with medium or lower proviral DNA levels, but it was detected in 11 (39.3%) of 28 samples with high HTLV-I proviral DNA levels, estimated as equal to or more than the proviral DNA of 10 ng of HUT102 (i.e., HUT102 cells were used as positive controls). The mean number of interleukin-2 receptor alpha (IL-2R alpha)-positive cells as a percentage of the total number of PBMCs was higher (13.2%) in the tax/rex mRNA-positive carriers with high proviral DNA levels than in the carriers who were mRNA negative (8.4%) (p = 0.004, Wilcoxon test). These results suggest that virus activation as indicated by the presence of tax/rex mRNA in asymptomatic carriers with high proviral DNA levels is associated with an elevation of the IL-2R alpha-positive cells in vivo.

Ocular manifestations in adult T-cell leukemia/lymphoma.

Ocular manifestations of adult T-cell leukemia/lymphoma (ATL) are rare events. However, several ocular lesions which resulted from human T-cell leukemia virus type I (HTLV-I) infection have been reported, including direct infiltration of ATL cells, cytomegalovirus retinitis, and HTLV-I-associated uveitis (HAU). The aim of this study was to characterize ocular involvement in ATL and to correlate these lesions with HTLV-I proviral DNA integration. Three patients with acute-type ATL and ocular lesions were evaluated hematologically and ophthalmologically. Analysis of HTLV-I proviral DNA was carried out with a standard Southern blot technique using DNA from abnormal lymphocytes in peripheral blood. Two patients developed intraocular lesions located within intermediate and/or posterior segments which were caused by infiltration of ATL cells. Ocular lesions in one patient, which were localized to the anterior-intermediate segment, closely resembled those of HAU. Analysis of HTLV-I proviral DNA revealed multiple integrations in all three patients. The present study indicated heterogeneity in ocular manifestations of ATL. Multiple HTLV-I proviral DNA integrations may be associated with intraocular involvement in this disease.

HTLV-I Gene Expression in Adult T-Cell Leukemia Cells Elicits an NK Cell Responsein Vitroand Correlates with Cell Rejection in SCID Mice

Human T-cell leukemia virus type I (HTLV-I) is the etiologic agent of adult T-cell leukemia (ATL). We have previously shown that the ATL cell line, RV-ATL, formed tumors when inoculated into severe combined immunodeficient (SCID) mice. In contrast, the HTLV-Iin vitro-transformed cell line, SLB-I, was nontumorigenic in SCID mice. ATL cells contain HTLV-I proviral DNA sequences but lack detectable viral gene expression, in contrast to HTLV-Iin vitro-transformed cells, which express all viral gene products. We investigated the role of HTLV-I gene expression in tumorigenesis by superinfecting RV-ATL cells with HTLV-I. The resulting cell line, HT-1RV, expressed HTLV-I. Injection of HT-1RV cells into SCID mice resulted in a reduced tumorigenic phenotype compared to the parental RV-ATL cells.In vitronatural killer (NK) cell cytotoxicity assays revealed that cell lines expressing HTLV-I gene products, SLB-I and HT-1RV, were sensitive to NK cell cytolysis. In contrast, nonexpressing RV-ATL cells were resistant to NK cell cytolysis. These studies indicate that lack of viral gene expression allows HTLV-I-infected cells to elude detection by murine NK cells and increases tumorigenicity in SCID mice. Thus the loss of HTLV-I gene expression in ATL cells may be an important mechanism by which leukemic cells escape immune surveillance in humans.

Quantification of HTLV-II proviral copies by competitive polymerase chain reaction in peripheral blood mononuclear cells of Italian injecting drug users, central Africans, and Amerindians.

To better correlate the burden of human T cell leukemia virus type I (HTLV-I) and type II (HTLV-II) infection with diagnostic and prognostic markers, we developed a new competitive polymerase chain reaction (PCR) assay for the quantitative determination of proviral copy numbers in infected cells. A competitive plasmid was constructed that carried a 112-bp fragment from a highly conserved region of the HTLV tax gene and that was further modified by inserting a sequence of 24 bp. This competitive PCR assay system can be used for the quantification of HTLV-I and HTLV-II proviral DNA as demonstrated by using HTLV-I- and HTLV-II-infected cell lines and/or patient material. We determined the HTLV-II proviral load in peripheral blood mononuclear cells (PBMCs) of 11 Italian injecting drug users (IDUs) infected by this virus and in PBMCs of 10 seropositive Amerindian and Central African individuals from endemically infected ethnic groups. A great variation was observed in the number of HTLV-II proviral sequences in the PBMCs of Italian drug abusers, ranging from 5-10 to 16,239 copies/10(5) cells. There was no clear-cut correlation between proviral load, CD8 count, stage of HIV-1 infection, and therapy. A considerable variation in HTLV-II proviral load was also observed in PBMCs of Amerindians and Central Africans with no correlation between the amount of HTLV-II provirus and the geographic origin of the infected individuals.

HTLV-I proviral DNA amount correlates with infiltrating CD4 + lymphocytes in the spinal cord from patients with HTLV-I-associated myelopathy

A quantitative method utilizing polymerase chain reaction was employed to evaluate the amount of human T-cell leukemia virus type I (HTLV-I) proviral DNA in the affected spinal cords from patients with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Central nervous system (CNS) tissues were obtained at post-mortem from five patients with HAM/TSP, who vary in the duration of illness from 2.5–10 years, and one patient with adult T-cell leukemia (ATL), who had leukemic cell infiltration in the CNS. The presence of HTLV-I pX and pol sequences in the CNS tissues were demonstrated in all patients examined. In HAM/TSP, the proviral DNA quantified in the thoracic cord was 0.002–2 copies per 100 tissue cells, and that in the peripheral blood mononuclear cells (PBMC) was 2–8 copies per 100 PBMC. The proviral DNA amount in the thoracic cord of the patient with ATL was 0.4 copies per 100 tissue cells. An apparent propensity for the amount of integrated HTLV-I in the thoratic cord to decrease with the disease duration in patients with HAM/TSP was observed. The decline in HTLV/I proviral DNA amount in the thoracic cord lesions was paralleled with the alteration of proportion of CD4 + T lymphocytes in patients with HAM/TSP. These findings suggest the preferential virus reservoir may be infiltrating CD4 + T lymphocytes in the spinal cord lesions of patients with HAM/TSP, and HTLV-I infection in the CNS of patients is declining with the disease duration in spite of the chronic course of neurological manifestations at least in some patients with HAM/TSP.

Establishment and Characterization of Synovial Cell Clones with Integrated Human T-Cell Leukemia Virus Type-I

Human T cell leukemia virus type-I (HTLV-I)-integrated synovial cell clones (SCCs) were established from four HTLV-I-infected patients with chronic proliferative arthropathy. Extracted DNAs of these SCCs were examined for the existence of HTLV-I proviral DNA. Electron microscopic analysis and immunohistochemical staining were also performed to examine the nature of the HTLV-I integrated SCCs. SCCs derived from all four patients consisted of either HTLV-I integrated or nonintegrated cells. HTLV-I integrated SCCs also produced viral messenger RNA which was detected by reverse transcriptase-polymerase chain reaction as well as viral protein which was detected by immunohistochemical staining. Phenotypically, these SCCs containing HTLV-I proviral DNA were shown to be all cell types as observed by electron microscopic analysis and immunohistochemical analysis. Moreover, expression of HTLV-I glycoprotein was greater in SCCs with a monocyte marker. These findings suggest that SCCs harboring HTLV-I have an important role in synovial hyperplasia.

Overgrowth of human synovial cells driven by the human T cell leukemia virus type I tax gene.

One of the salient pathological features of rheumatoid arthritis is synovial cell proliferation with bone erosion. Despite extensive investigation, the factors essential for synovial cell proliferation remain to be identified. Recent studies suggest that human T cell leukemia virus type I (HTLV-I) may play an important role in synovial overgrowth observed in patients with one type of chronic inflammatory synovitis. In order to confirm and extend these observations, we have established synovial cell clones (SCCs) from three HTLV-I carriers who demonstrated synovial overgrowth but were otherwise asymptomatic. HTLV-I proviral DNA randomly integrated into the cellular genome was present in 20-30% of SCCs. The SCCs carrying HTLV-I proviral DNA and expressing the tax gene exhibited high levels of proliferative potential. HTLV-I was found to function as a transcriptional trans-activator in these SCCs. Moreover, transfection of the tax expression plasmid into SCCs resulted in the same phenotype of increased proliferation and cytokine expression as exhibited by HTLV-I provirus-carrying and tax-expressing SCCs. These data suggest that tax plays a critical role not only in leukemogenesis but also in synovial overgrowth in humans.

RHEUMATIC MANIFESTATION OF HUMAN LEUKEMIA VIRUS INFECTION

Rheumatic disorders associated with retroviruses are described in this article. A recent study of human T-cell leukemia virus type-I (HTLV-I) revealed that it appeared to be associated with the pathogenesis of several immune disorders such as myelopathy, broncho-pneumopathy, Sjogren's syndrome, and arthropathy. HTLV-I-associated arthropathy (HAAP) shows remarkable synovial proliferation with nuclear convoluted T-cell infiltration in both synovium and synovial fluid. Synovial cells obtained from HAAP patient-integrated HTLV-I proviral DNA and also expressed mRNA for HTLV-1 tax gene; moreover, HTLV-1 integrated synovial cell clones expressed a high level of mRNA for several oncogene and growth factors compared with HTLV-I non-integrated clones. These findings suggest that HTLV-I is the first exogenous retrovirus that contributes to synovial proliferation with immune disorders in humans.

Fluctuation of HTLV-I proviral DNA in peripheral blood mononuclear cells of HTLV-I-associated myelopathy

To assess the immunopathological significance of the increased replication of human T-cell leukemia virus type I (HTLV-I) in HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) we investigated the dynamics of HTLV-I proviral DNA in peripheral blood mononuclear cells (PBMC) of HAM/TSP patients at different clinical stages. We compared the dynamics to those of asymptomatic HTLV-I carriers (AC). The estimation of the amount of HTLV-I proviral DNA was carried out by quantitative polymerase chain reaction of serially diluted DNA samples where it was feasible to titrate 0.04–80 copies per 100 PBMC. The proviral DNA quantified in six patients with HAM/TSP was 2–20 copies per 100 PBMC, while that in eight cases of AC was 0.04–8 copies per 100 PBMC. Thus, the amount of HTLV-I proviral DNA in HAM/TSP patients was 3–50 times as high as that of AC. When we followed up HAM/TSP patients for 1–3 years, the amount of HTLV-I proviral DNA fluctuated from 4 to 10-fold. These data suggest that the rate of HTLV-I replication increases in HAM/TSP and the amount of HTLV-I proviral DNA fluctuates in their clinical course. Fluctuation in the amount of HTLV-I proviral DNA may reflect dynamics of HTLV-I infected cell proliferation and immunological suppression in vivo in HAM/TSP patients.

Analysis of anti‐tax antibody of HTLV‐I carriers in an endemic area in Japan

Sera from 1197 adult residents in Miyazaki district, an area in Japan endemic for human T-cell leukemia virus type I (HTLV-I), were tested for anti-Tax antibody by the recombinant Tax (r-Tax) Western blot assay. Among HTLV-I-seropositive individuals, including 21.5% of 484 males and 28.6% of 713 females, the prevalence of anti-Tax antibody were 59.6% and 58.3% respectively, with no apparent difference in age. There was a significant 6-fold difference in the prevalence of anti-Tax among seropositive subjects with titer > or = 1:8192 (84.6%) compared with those with the lowest titer of 1:16 (14.3%), suggesting the increased production of antibodies to viral structural proteins in anti-Tax-positive individuals. Furthermore, among those anti-Tax-positive subjects, the intensity of serum reactivity to r-Tax protein in the high antibody titer (1:1024 or higher) group was significantly stronger than that in the lower antibody titer (1:512 or lower) group. We also found that 1.6% (14/889) of individuals without detectable levels of HTLV-I antibody had anti-Tax antibody. HTLV-I pro-viral DNA signals could not be detected in DNA sample from the lymphocytes of these individuals by the nested polymerase chain reaction method. Further evaluation is needed to clarify the significance of an anti-Tax-only status population in which HTLV-I is endemic.

Human T-cell leukemia virus type I(HTLV-I) infection of T cells bearing T-cell receptor gamma delta: effects of HTLV-I infection on cytotoxicity.

In order to clarify the cellular tropism of human T-cell leukemia virus type I (HTLV-I) and the effects of HTLV-I infection on T-cell functions, we investigated the infectiousness of HTLV-I on T cells bearing T-cell receptor (TCR) gamma delta and functional alterations of the HTLV-I-infected TCR-gamma delta + T cells. CD3+ CD4-CD8-TCR-gamma delta + T-cell clones which possessed cytotoxicity were co-cultured with a HTLV-I-producing T-cell line. After several weeks, integration of HTLV-I proviral DNA in TCR-gamma delta + T cells was detected by Southern blot analysis. During the continuous culture of HTLV-I-infected TCR-gamma delta + T-cell clones, 2 distinct phases were observed in terms of cytotoxic activity and expression of the CD3-TCR-gamma delta complex. Early after HTLV-I infection, TCR-gamma delta + T cells lost their spontaneous cytotoxicity, but this was restored by the addition of lectin. At this time, no differences were observed in the expression of various surface molecules between HTLV-I-infected and uninfected parent cells, except for increased expression of CD25 on HTLV-I-infected cells. At about 30 weeks after HTLV-I infection, the cytotoxicity of HTLV-I-infected cells was almost completely lost, even in the presence of lectin, and expression of the CD3-TCR-gamma delta complex on the cell surface was markedly decreased. Concomitant with the decreased expression of CD3-TCR-gamma delta complexes, a decrease in the elevation of cytoplasmic Ca2+ concentration induced by anti-CD3 and anti-TCR monoclonal antibodies (MAbs) was also observed. Our present findings thus show that HTLV-I can infect TCR-gamma delta + T cells, and that consequently their functions are profoundly affected through 2 distinct phases.

Major prognostic factors of Japanese patients with lymphoma‐type adult T‐cell leukemia

Fifty-three Japanese patients with the lymphoma-type adult T-cell leukemia (ATL) were analyzed to study the prognostic value of various clinical findings recorded at the time of diagnosis. All patients were positive for human T-cell leukemia virus type I (HTLV-I) antibody and demonstrated monoclonal integration of HTLV-I proviral DNA in their malignant cells. The important individual variables detected in a previous univariate analysis were placed in a multiple regression model to identify the major prognostic factors for survival. This analysis showed that serum lactate dehydrogenase (LDH), calcium, and total protein levels had a strong predictive relationship with the length of survival (in descending order of importance). Among the 53 patients, 46 were dead at the time of analysis. The cause of death in relation to the duration of survival is also reviewed in this article.

Differences in Prognostic Factors between Diffuse Non-Hodgkin's Lymphoma and Lymphoma Type of Adult T-Cell Leukemia

Sixty-four Japanese patients with diffuse non-Hodgkin's lymphoma (NHL) were classified into human T-cell leukemia virus type I (HTLV-I) non-related diffuse NHL (41 cases) and HTLV-I related diffuse NHL, i.e. lymphoma type of adult T-cell leukemia (ATL-lymphoma, 23 cases) on the bases of serological detection of HTLV-I antibody and the detection of HTLV-I proviral DNA in malignant cells. The survival curves between diffuse NHL and ATL-lymphoma were quite different. Therefore, it is important to know the differences in prognostic factors, if any, affecting the survival in two groups: diffuse NHL and ATL-lymphoma cases. In diffuse NHL patients, factors found to be important were age, performance status, stage, organ involvement, hemoglobin concentrations and platelet count in the peripheral blood, serum lactic dehydrogenase (LDH) and calcium levels. However, none of these factors were useful for ATL-lymphoma patients, except for the serum calcium level. Thus, prognostic factors should be considered separately for diffuse NHL and ATL-lymphoma.