Natural antibodies to the structural core protein (p24) of the human T-cell leukemia (lymphoma) retrovirus found in sera of leukemia patients in Japan

In Japan, adult T-cell leukemias and lymphomas are more common than in the United States and Europe, and in the southwest part of Japan these T-cell malignancy cases appear in clusters. Therefore, we investigated the involvement in these leukemias and lymphomas of the human T-cell leukemia virus (HTLV) that was previously isolated in one of our laboratories from cultured T cells of some patients in the United States with leukemias and lymphomas involving relatively mature T cells. High titers of antibodies capable of quantitative precipitation of ¹²⁵I-labeled p24, a well characterized core protein of HTLV, were detected in 12 of 12 patients with untreated adult T-cell leukemia (ATL). (One negative was a patient on chemotherapy.) Ten of the 12 positive samples were from an area where the disease is endemic. Strong precipitating antibodies were also detected in five of seven cases of T-cell malignant lymphoma (TML) which differs from ATL by having fewer leukemic cells in the peripheral blood. High antibody titers were also observed in one of five cases of acute monoblastic leukemia and one of eight cases of chronic myelogenous leukemia in the blast phase of the disease. Low to moderate titers of antibodies were detected in several categories of leukemia (two cases of blast-phase chronic myelogenous leukemia, two cases of acute lymphoblastic leukemia of the null-cell type, and one case of acute myelogenous leukemia). Among all categories of leukemias, except ATL and TML, more cases were negative than positive for anti-p24 activity. All of 79 sera from normal Japanese, including 39 collected from the endemic ATL area of southwest Japan, were negative for antibodies to HTLV p24. All the positive reactivities observed were highly specific to HTLV. The only competition observed in the precipitation of HTLV p24 was with HTLV or with cell lines expressing HTLV and not with various animal retroviruses or a large number of human and subhuman primate cell lines, not known to be producing HTLV. The data strongly indicate an association of HTLV with the increased incidence of ATL in parts of Japan, probably with other forms of leukemias in Japan, and, less commonly, with certain T-cell malignancies in the United States.     

Failure of regulation of Tac antigen/TCGF receptor on adult T-cell leukemia cells by anti-Tac monoclonal antibody

Anti-Tac monoclonal antibody, which blocks the membrane binding and action of human T-cell growth factor (TCGF), is strongly proposed to recognize TCGF receptor. We have demonstrated that anti-Tac antibody reacted with leukemic cells from patients with adult T-cell leukemia (ATL) and reacted with T-cell lines established from ATL cells. Although antigenic modulation, or down-regulation, of Tac antigen on activated normal T cells was induced by anti-Tac antibody, the expression of Tac antigen on ATL cells or T-cell lines was not affected when examined by the fluorescence-activated cell sorter (FACS) and the radioassay using 125I-staphylococcal protein A. These results indicate that regulation of Tac antigen-TCGF receptor is different between normal and malignant T cells, suggesting that failure of down- regulation of Tac antigen on leukemic cells by anti-Tac antibody may play an important role in the malignant proliferation of ATL cells.     

Characterization and regulation of interleukin-4 receptor in adult T-cell leukemia cells

We studied the expression of the receptor of interleukin (IL)-4, one of the T cell growth factors, on fresh peripheral blood leukemic cells from adult T-cell leukemia (ATL) patients. Flow cytofluorometric analysis with a monoclonal antibody to the IL-4 receptor (IL-4R) were used to investigate whether expression of IL-4R on ATL cells is different from that on normal lymphocytes and other types of leukemic cells. Leukemic cells from acute type ATL patients synthesize IL-4R without stimulation, at levels much higher than normal resting lymphocytes and other types of leukemic cells. Furthermore, leukemic cells from acute type ATL showed higher IL-4R expression than that of chronic type ATL or human T-cell leukemia virus type I carriers. In addition, there was correlation between expression of IL-4R on the cell surface and the proliferative response to IL-4. Both IL-4 and IL-2 induced upregulation of IL-4R on activated normal T cells but not on ATL cells. These results suggest that abnormal expression of IL-4R may display different biological activities in ATL compared with other types of leukemia. Furthermore, the high expression of IL-4R in ATL may be involved in the proliferation of leukemic cells and the leukemogenesis in this disease.     

A model of in vivo cell proliferation of adult T-cell leukemia

We have made a model of in vivo cell proliferation of leukemic cells from adult T-cell leukemia (ATL) patients using severe combined immunodeficiency (SCID) mice. Peripheral blood mononuclear cells (PBMC) or lymph node cells (LNC) depleted of B cells and monocytes were intraperitoneally injected into SCID mice treated with antimurine interleukin-2 receptor (IL-2+) beta chain monoclonal antibody (MoAb)(TM- beta 1), followed by daily injection of human recombinant IL-2 until 60 days after cell injection. SCID mice injected with ATL cells from 6 of 8 ATL patients were found to have the tumor or leukemia 5 to 7 weeks after the inoculation of cells. Serum levels of soluble form of human IL-2R alpha chain (Tac) were markedly elevated in such mice. The cells recovered from the mice injected with leukemic cells from four different ATL patients had the same cell surface phenotype as that of original leukemic cells which were CD4+Tac+. Furthermore, we detected the same integration site of human T-cell leukemia virus type I (HTLV- I) provirus and the same rearrangement pattern of human T-cell receptor (TCR) beta chain gene as those of ATL cells by Southern blot hybridization, indicating that the cells proliferating in SCID mice were derived from the original ATL cell clone. Histologic examination showed that the pattern of the infiltration of ATL cells into various organs in SCID mice was similar to that of an ATL patient. Such a model of in vivo cell proliferation of ATL cells will be useful for the study of the mechanism of neoplastic cell proliferation and for the development of a new and effective treatment of ATL.     

Surface phenotype of Japanese adult T-cell leukemia cells characterized by monoclonal antibodies

We studies the surface phenotype and the functional activities of leukemic cells from three patients with Japanese adult T-cell leukemic (ATL) using the panel of OK and anti-Tac monoclonal antibodies, which react with differentiation antigens and define functionally distinct T- cell subsets or activated and terminally differentiated T cells. The phenotype of ATL cells were determined to be OKT1+T3+T4+T10+T5-T8-Okla1- , although cells from two patients suppressed pokeweed mitogen (PWM) induced normal B-cell differentiation, and cells from all patients lacked helper activity in this system. In addition, after cultivation with PWM, ATL cells from all patients were reactive with anti-Tac monoclonal antibody, and cells from one patient were reactive with OKlal. These findings suggest that ATL cells arise from peripheral mature T-cell subsets and also suggest that the transition of surface phenotype of ATL cells to functionally mature and activated T cells occurs in culture.     

Protection from graft-versus-host disease with a novel B7 binding site-specific mouse anti-mouse CD28 monoclonal antibody

We studied the role of CD28 in T-cell biology and T cell-mediated pathology using a novel mouse anti-mouse CD28 antibody, E18, which recognizes an epitope close to the B7 binding site. In vitro, this antibody completely blocked binding of B7 molecules to CD28 expressed on mouse thymocytes but enhanced anti-CD3-induced proliferation of peripheral T cells. Injections of E18 monoclonal antibody into normal BALB/c mice in vivo, however, led to a reversible reduction in Treg cell frequencies among CD4(+) cells, both in the thymus and in secondary lymphoid organs, suggesting that E18 acted as an inhibitor of CD28 signaling under these conditions. Antagonistic activity of E18 in vivo was further implied by suppressed responses of conventional CD4(+) T cells to stimulation with the superantigen staphylococcal enterotoxin B and in a model of acute graft-versus-host disease. In contrast to healthy mice, intact monoclonal antibody E18, but not its nonstimulatory Fab fragment, increased the frequencies of Treg cells among CD4(+) T cells in these pro-inflammatory settings allowing for efficacious protection from acute graft-versus-host disease. Thus, the agonistic signal generated by conventional, ie, nonsuperagonistic, anti-CD28 antibodies is important for their immunotherapeutic potential in vivo.     

How I treat adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) is an aggressive malignancy of mature activated T cells caused by human T-cell lymphotropic virus type I. ATL carries a bad prognosis because of intrinsic chemoresistance and severe immunosuppression. In acute ATL, Japanese trials demonstrated that although combinations of chemotherapy improved response rate, they failed to achieve a significant impact on survival. Patients with chronic and smoldering ATL have a better prognosis, but long-term survival is poor when these patients are managed with a watchful-waiting policy or with chemotherapy. Recently, a worldwide meta-analysis revealed that the combination of zidovudine and IFN-α is highly effective in the leukemic subtypes of ATL and should be considered as standard first-line therapy in that setting. This combination has changed the natural history of the disease through achievement of significantly improved long-term survival in patients with smoldering and chronic ATL as well as a subset of patients with acute ATL. ATL lymphoma patients still benefit from chemotherapy induction with concurrent or sequential antiretroviral therapy with zidovudine/IFN. To prevent relapse, clinical trials assessing consolidative targeted therapies such as arsenic/IFN combination or novel monoclonal antibodies are needed. Finally, allogeneic BM transplantation should be considered in suitable patients.     

Surface antigenic phenotypes of human T-cell leukemia corresponding to those of post-thymic T cells

Leukemic cells from eight adult patients with various types of T-cell leukemias, including one patient with lymphosarcoma cell leukemia (T-LSL), two patients with chronic lymphocytic leukemia (T-CLL), and five patients with adult T-cell leukemia (ATL), were analyzed for their surface antigenic phenotypes with a series of monoclonal antibodies directing to human T-cell differentiation antigens. All of the leukemic T cells studied were regarded as being of post-thymic T-cell origin because of their ability to form rosettes with sheep red cells under the condition at 4^oC but not 37^oC as well as the expression of human Ly-1-like but not TL-like antigen on their cell surfaces. By using monoclonal antibodies to a variety of human T-cell antigens (Leu-1, Leu-2a, and Leu-3a), all eight cases could be divided into either group of three distinct categories. Thus, one patient with T-LSL had cells with Leu-1⁺2a⁺3a⁺ phenotype, which might reflect possible post-thymic precursor T cells, whereas one patient with T-CLL had cells with the same phenotype (Leu-1⁺2a⁺3a^-) as normal cytotoxic/suppressor T cells. The latter cells also expressed Ia antigens as defined by monoclonal antihuman Ia antibody. The remaining six cases, including one T-CLL and five ATL patients, had leukemic cells with the same phenotype (Leu-1⁺2a^-3a⁺) as normally found on helper/inducer T cells, despite distinct clinical and immunological features between T-CLL and ATL. Some clinical findings observed in those patients may reflect functional activities retained by their leukemic T cells.     

A monoclonal antibody detecting a novel antigen expressed in the HTLV-I- infected cells

A monoclonal antibody, FTF 148, was prepared by hybridizing murine myelomal cells (NS-1) and spleen cells of BALB/c mice immunized with cultured cells derived from an adult T cell leukemia (ATL) patient (KUT- 2 cells). This monoclonal antibody reacted with all of the human T cell leukemia virus I (HTLV-I)-infected cell lines tested but did not react with other T cell lines derived from acute lymphocytic leukemia, Epstein-Barr virus-transformed B cell lines, or an erythroleukemic cell line. This monoclonal antibody was not directed to viral antigens because it reacted equally well with almost all KUT-2 and MT-1 cells, only 1% to 3% of which were ATL-associated antigen-positive. In contrast to interleukin 2 receptors expressed on both ATL cells and normal phytohemagglutinin-stimulated blasts, this antigen was not expressed on the latter cells. The antigen, mainly expressed on the cell membrane, was analyzed by metabolic labeling with 3H-leucine and surface labeling with 125I followed by cell lysis and immunoprecipitation with the FTF 148 antibody. The findings obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that p50 and p74 proteins were specifically precipitated and the antigen was also different from the product of the Xs gene of HTLV-I.     

Recent advances in clinical research on T-cell lymphoma

Immunophenotypic analysis on 34 cases of T-cell malignancies using monoclonal antibodies against T-cell receptors (TCR) revealed 25 cases of alpha beta-type and two of gamma delta-type. The two patients with gamma delta-type showed cutaneous involvement of tumor cells. Immunoblastic lymphadenopathy (IBL)-like T-cell lymphoma is divided into three histologic categories; inconspicuous type, patchy type and diffuse type. DNA hybridization analysis revealed that 11 of 16 cases showed clonal rearrangement of TCR beta-chain gene without rearrangement of immunoglobulin heavy chain gene, providing strong evidence for clonal proliferation of T-cells. Among 185 patients with adult T-cell leukemia (ATL), 18 cases (9.7%) were found not to be associated with human T-cell leukemia virus type I (HTLV-I). They consisted of 10 of acute type, five of chronic type, two of lymphoma type and one of smoldering type, indicating a diversity in clinical features. Two Japanese patients with ATL developed secondary monoclonal B-cell lymphomas of diffuse, large cell, non-Burkitt type. They were seropositive for HTLV-I but negative for human immunodeficiency virus (HIV). They also suffered from pulmonary tuberculosis, and one from adenovirus type 11-induced hemorrhagic cystitis, indicating an immunodeficient state. Epstein-Barr virus genome was found in lymphoma cells from one patient. It is suggested that opportunistic B-cell lymphomas may occur in the immunodeficient stage of ATL.     

Transferrin receptor induction in mitogen-stimulated human T lymphocytes is required for DNA synthesis and cell division and is regulated by interleukin 2.

Transferrin is required by many cells for growth. Mitogen-induced T lymphocyte proliferation is dependent on the presence of both interleukin 2 (IL-2; T-cell growth factor) and transferrin, even though resting lymphocytes do not have receptors for either. Exposure to mitogen (phytohemagglutinin) alone is sufficient to induce transient appearance of IL-2 receptors on lymphocytes. Using monoclonal antibodies to the IL-2 receptor and to the transferrin receptor, we examined those signals required for transferrin receptor induction during T lymphocyte proliferation. Our study has revealed that (i) monocytes, or a monocyte substitute such as the phorbol ester tetradecanoylphorbol 13-acetate, are required for transferrin receptor expression after mitogen exposure; (ii) the presence of IL-2 receptors is necessary for transferrin receptor induction; (iii) antibody to the IL-2 receptor inhibits thymidine incorporation (DNA synthesis) in lymphocytes, but only if administered before transferrin receptors have appeared; and (iv) antitransferrin receptor antibody inhibits DNA synthesis but has minimal effect on IL-2 receptor expression. Thus, IL-2 receptor induction leads to transferrin receptor induction and subsequent initiation of DNA synthesis. These data indicate that IL-2 stimulates T lymphocyte proliferation, at least in part, by induction of transferrin receptors on these cells.     

Increased density of ecto 5' nucleotidase antigen on leukemic T cells from patients with cutaneous T-cell lymphoma and adult T-cell leukemia/lymphoma

Malignant CD4+ T cells in adult T-cell leukemia/lymphoma (ATL) and cutaneous T-cell lymphoma (CTCL) express a number of cell surface molecules that are upregulated on normal T cells activated by foreign antigen. In this report we describe an interesting exception to the parallel phenotypic features of activated T cells and malignant CD4+ T cells. A monoclonal antibody (MoAb; termed 27.2) that was raised to HTLV-1+, CD4+25+ leukemic T cells stained weakly 25% of peripheral T cells, including approximately 50% of CD8+ T cells and 20% of CD4+ T cells. Flow cytometry analysis indicated that the surface density of the 27.2 antigen was unchanged or diminished when normal T cells were activated by antigen. However, 3/4 Sezary cases and 4/8 cases of ATL had relatively high densities of the 27.2 antigen. Immunoprecipitation and sodium dodecylsulfate polyacrylamide gel electrophoresis of the NP-40-solubilized membranes of surface-iodinated ATL cells indicated that MoAb 27.2 reacted with a 75 Kd molecule. The size and distribution of the 27.2 antigen on T cell subsets suggested that it might be the enzyme ecto-5' nucleotidase (NT), a phosphatidylinositol-linked enzyme that catalyzes dephosphorylation of monophosphate nucleotides to their respective nucleosides. This was confirmed by demonstrating that lymphocyte ecto-5'NT activity was blocked partially and inhibited completely by preincubating cells with MoAb 27.2 for 1 hour at 4 degrees C and 24 hours at 37 degrees C, respectively. When used with a second MoAb (27.1) to a novel T cell activation antigen found on all CTCL and ATL leukemias examined, 27.2 was found to discriminate between normal and leukemic T cells in two patients with ATL. These studies suggest that ecto-5'NT has diagnostic value in T cell malignancies and may be aberrantly expressed in some cases of ATL and CTCL.     

Enzyme analysis of lymphoproliferative diseases: a useful addition to cell surface phenotyping

Lymphocytes from patients with acute and chronic T-cell malignancy or chronic T gamma lymphocytosis were characterized by studying the activity of three enzymes involved in purine metabolism and by determining the isoenzyme pattern of lactate dehydrogenase (LDH) in addition to analysis of surface marker expression with monoclonal antibodies. Four clinically different types of disease were distinguished on the basis of the enzyme parameters. Lymphocytes from patients with acute lymphocytic leukemia (T-ALL) showed an enzyme profile similar to that of normal thymocytes, i.e., an elevated level of adenosine deaminase (ADA) activity as compared with normal T lymphocytes, reduced activities of purine 5'nucleotidase (5'NT) and purine nucleoside phosphorylase (PNP), and a binomial distribution of the LDH isoenzyme pattern. Cells from "null"-ALL patients had an ADA/PNP ratio that was intermediate between that of normal T cells and that of T-ALL cells or thymocytes, but their 5'NT activity and LDH isoenzyme pattern were thymocyte-like. Patients with chronic T-cell proliferation were subdivided into those with chronic T gamma lymphocytosis and those with proven chronic T malignancy. The lymphocytes from these patients had ADA and PNP activities within the ranges of those of normal T lymphocytes. However, the ADA activity and/or the ADA/PNP ratio were consistently higher in the cells from the patients with chronic T gamma lymphocytosis than in those with chronic T malignancy. The enzyme profile of the cells from the T gamma patients was similar to that of T gamma cells of normal individuals. The cells from patients with chronic T malignancies showed a heterogeneous enzyme pattern as compared with that of normal T lymphocytes. Analysis with monoclonal antibodies enabled us to distinguish null-ALL patients from the other leukemias studied, but a distinction between chronic and acute T-cell proliferation disease, for instance, was not possible with monoclonal antibodies alone. Our data demonstrate that the enzyme profiles studied provide supplementary information for classification and diagnosis of lymphoproliferative diseases to that obtained with cell surface markers alone.     

Intravenous or cold ex vivo administration of monoclonal antibodies for conditioning of rat small-bowel allografts

The following study describes cold ex vivo or intravenous infusion of monoclonal antibodies (MCAB) for lymphocyte target cells of rat small-bowel grafts. The MCAB Ox8, directed against CD8+ T lymphocytes, is used here as a model antibody. We demonstrate that Ox8 antibodies administered during cold ex vivo perfusion are able to reach the target cells in the small-bowel mucosa and the mesenteric lymph nodes of rat small-bowel grafts. Thus, cold perfusion of the vascular system for 20-60 min resulted in good labelling of the CD8+ T cells as analysed on cryostat tissue sections using immunoperoxidase staining. Rats treated with Ox8 intravenously 60 min before taking of specimens showed similar labelling. Additional staining of the tissue sections with Ox8 antibody resulted in no further labelling, thus indicating that nearly all CD8+ T cells were labelled both after ex vivo perfusion and after intravenous treatment of the donor. It is concluded that MCAB can, as an alternative to the intravenous route, be administered ex vivo after organ harvesting.     

Activation of resting human B cells by helper T-cell clone supernatant: characterization of a human B-cell-activating factor.

The effects of helper T-cell clone supernatants on resting human B cells were investigated. Four different helper T-cell clones (two T4+ and two T8+) were stimulated by anti-T3 monoclonal antibodies on Sepharose beads or anti-T11(2) plus anti-T11(3) monoclonal antibodies. The supernatants from these activated clones induced the proliferation of highly purified resting B lymphocytes from the peripheral blood. The B cells exhibited a cell size and a surface-antigen pattern (4F2 antigen and transferrin receptor) of phase G0 B cells, and they were functionally resting. In response to T-cell supernatants a large fraction of the B cells enlarged and expressed 4F2 antigens and transferrin receptors. In gel filtration, the corresponding activity migrated with an apparent Mr of 12,000-15,000. Our findings strongly support the existence of a human B-cell-activating factor acting on resting B cells and causing them to enter phase G1 of the cell cycle.     

A novel diagnostic method of adult T-cell leukemia: monoclonal integration of human T-cell lymphotropic virus type I provirus DNA detected by inverse polymerase chain reaction

Adult T-cell leukemia (ATL) is neoplasm of the mature helper T lymphocytes and human T-cell lymphotropic virus type-I (HTLV-I) has been shown to be causative virus of ATL. Because HTLV-I integrates its provirus randomly into host chromosomal DNA, monoclonal integration of HTLV-I provirus indicates the clonal proliferation of HTLV-I-infected cells. Therefore, demonstration of clonality of HTLV-I proviral DNA is essential to diagnosis of ATL. Southern blot analysis was used for this purpose. We developed the novel method using inverse polymerase chain reaction (IPCR) to detect the clonality of HTLV-I proviral DNA. This method identified the clonality in all ATL cases. Diagnosis could be made within 3 days using this method. It enabled us to detect specifically the presence of minimal numbers of ATL cells with high sensitivity. It also identified the monoclonal or oligoclonal proliferations of HTLV-I-infected cells in HTLV-I carriers and the intermediate state, in which no clonality could be shown by conventional Southern blot analyses. This finding indicated that even HTLV-I carriers had monoclonal proliferation of HTLV-I-infected cells without any symptoms. This novel method is shown to be useful for the diagnosis of ATL and provides information on the natural course of HTLV- I infection.     

Transferrin receptor expression on AML blasts is related to their proliferative potential

Expression of the transferrin receptor (TfR) was studied on peripheral blood blast cells from 11 patients with acute myeloid leukaemia (AML). Using a monoclonal anti-TfR antibody (OKT9) and a polyclonal antibody against surface membrane-bound transferrin, a proportion of blasts from all the patients was found to express receptors for transferrin. Further analysis of OKT9 expression using a fluorescent activated cell sorter (FACS) showed that the TfR was heterogeneously distributed in the blast cell population. In five out of six samples studied, stimulation of DNA synthesis following short-term culture induced a several-fold increase in TfR display as analysed by flow cytometry using OKT9 or FITC-conjugated transferrin. Blasts from seven patients stained with OKT9 were separated on the FACS into positive and negative or weakly positive fractions. Culture of the TfR negative population in a blast cell colony assay produced no colonies in either of two patients. In a further five patients the colony forming cells were predominantly associated with the TfR strongly positive fraction (52 +/- 25 colonies/10(4) cells) rather than the TfR weakly positive fraction (12 +/- 11 colonies/10(4) cells). Analysis of colony size showed that clones derived from the weakly positive fraction were smaller than clones from the TfR strongly positive fraction. These results suggest that TfR display by AML blasts is related to their proliferative capacity and is expressed by the leukaemic stem cell fraction.     

Functional role of HLA class I cell-surface molecules in human T-lymphocyte activation and proliferation

This investigation addressed the role of major histocompatibility complex-encoded class I molecules in the activation and proliferation of human lymphocytes. We studied the effect of antibodies specific for HLA-A and HLA-B locus gene products on mitogen-stimulated peripheral blood mononuclear cell (PBMC) subpopulations. Three individually derived, well-characterized anti-HLA class I monoclonal antibodies were demonstrated to inhibit the proliferation of human PBMC stimulated by either OKT3 or the calcium ionophore ionomycin. The antibody directed against HLA-A, -B, and -C locus gene products (W6/32) and the antibody directed against HLA-B locus gene products (4E) inhibited proliferation induced by either mitogen by 70-90%. The HLA-A locus-specific antibody (131), though inhibiting ionomycin-induced proliferation by 80-90%, was much less effective when OKT3 was the stimulus. The inhibition affected T4+ and T8+ cells and was not mediated by DR+ accessory cells. The inhibitory effect of these antibodies was associated with a decrease in the level of interleukin 2 activity present in culture supernatants, decreased interleukin 2 receptor expression, and decreased transferrin receptor expression and was not overcome by the addition of exogenous interleukin 2. Our results suggest that HLA class I molecules are directly involved in the early critical events of human lymphocyte activation and proliferation.     

Studies on association between the ATL and the development of multiple malignant neoplasms--analysis of 1171 cases of hematological malignancies during the past 24 years

A high incidence of multiple primary neoplasms has been observed in our patients with ATL in comparison to persons with other forms of hematologic malignancy who we have observed during the past 24 years (1963-1985). Five of 15 patients with ATL (33.3%) have had at least one other associated neoplasm in comparison to only 44 of 1156 patients with other forms of hematological malignancy (3.8%). The incidence figures for secondary neoplasms associated with the other hematologic malignancies were 4.3% (16/370) for acute non-lymphocytic leukemia (ANLL), 2.2% (2/90) for acute lymphocytic leukemia (ALL), 4.8% (1/21) for acute unclassifiable leukemia, 2.2% (5/225) for chronic myelogenous leukemia, 4.7% (2/43) for chronic lymphocytic leukemia, 5.9% (8/136) for malignant monoclonal gammopathy and 3.7% (10/271) for malignant lymphoma. The incidence of multiple neoplasms in patients with ATL in comparison to those with other hematological malignancies was significant (p less than 0.01 or p less than 0.001). The neoplasms associated with ATL have been adenocarcinoma of the thyroid or lung, and squamous cell carcinoma of the larynx, lip or lung. We identified ATL-derived factor (ADF) in the cytoplasm of the secondary neoplasms of the ATL patients by means of indirect immunofluoroscopy and immunohistochemical techniques utilizing anti-ADF antibody. We also identified ras p21 products in these neoplasms by means of p21 ras monoclonal antibody studies. The possibility that HTLV-I was the cause of the secondary neoplasms thus was investigated.(ABSTRACT TRUNCATED AT 250 WORDS)