A distinct subtype of idiopathic myelofibrosis with bone marrow features mimicking hairy cell leukemia: evidence of an autoimmune pathogenesis

A young female patient presented with severe anemia and myelofibrosis. The spleen was not enlarged on clinical examination and no leukoerythroblastosis or tear-drop poikilocytosis was found. A bone marrow biopsy disclosed severe myelofibrosis and many megakaryocytes, which appeared morphologically normal. A striking feature was a heavy spongy infiltration by large lymphocytic cells, which were tartrate-resistant acid phosphatase negative and without hairy projections. This bone marrow appearance highly resembled the clear cell appearance of the hairy cell infiltrate in hairy cell leukemia. A diagnosis of acute autoimmune myelofibrosis was made. During high-dose glucocorticoid therapy the bone marrow fibrosis completely resolved and there was an improvement of peripheral blood values. The disorder is supposed to feature a distinct clinicopathological entity within the syndrome of idiopathic myelofibrosis. The disease should be considered in the differential diagnosis of patients with myelofibrosing disorders, including acute myelofibrosis and hairy cell leukemia.     

Leukopenic chronic T cell leukemia mimicking hairy cell leukemia: association with human retroviruses

We report two cases of a T cell lymphoproliferative disease not previously described, with cytologic and clinical features similar to those associated with Galton's "prolymphocytic" leukemia (PL). Our patients, like those with Galton's PL, had massive splenomegaly and minimal or absent hepatomegaly and lymphadenopathy. In contrast, however, our patients had leukopenia, as well as low percentages of leukemic cells in the peripheral blood and in the bone marrow. In splenic imprints, the nuclear chromatin pattern of most of the leukemic cells was intermediate between those of mature lymphocytes and those of lymphoblasts, and the nuclei contained single, centrally located, conspicuous nucleoli. In sections of the spleen, the leukemic cells diffusely infiltrated the red pulp in a pattern strikingly similar to that of hairy cell leukemia; however, when the leukemic cells were studied cytochemically, the cytoplasmic acid phosphatase positivity was punctate and tartrate-sensitive. The leukemic cells were sheep erythrocyte rosette-positive and expressed T cell-associated antigens. Initially, both patients responded well to therapeutic splenectomy. One patient received combination chemotherapy after splenectomy and is alive and well 24 months after diagnosis. The other patient was in complete clinical remission for one year after splenectomy and received chemotherapy at relapse. He died, however, 23 months after splenectomy, with disseminated disease. IgG antibody titers against human T lymphotropic virus type I (HTLV-I) were detected in one patient and against HTLV-II in the other. The leukemia in these patients represents a distinct clinicopathologic entity within the spectrum of peripheral T cell lymphoproliferative diseases that includes Galton's PL of T cell derivation, T cell chronic lymphocytic leukemia, T cell hairy cell leukemia, and adult T cell leukemia/lymphoma.     

A two-color flow cytometry assay for detection of hairy cells using monoclonal antibodies

We have developed a simple two-color immunofluorescence assay equally suited for microscopy and flow cytometry detecting hairy cells (HCs) in single cell suspensions, based on the concomitant reactivities with the B cell-specific monoclonal antibody B1 (CD20) and the monocyte/HC- associated antibody SHCL-3 (CD11c). Thus, HCs can be demonstrated in peripheral blood, bone marrow, and spleen specimens from hairy cell leukemia (HCL) patients even when they constitute less than 1% of the cell suspension. Likewise, admixture experiments with normal mononuclear cells and the MOLT-4 T-acute lymphocytic leukemia (ALL) cell line demonstrated that HCs could be detected in amounts as low as 1%. The validity of this assay has been ascertained by the lack of double marker positivity in cell suspensions from B-chronic lymphocytic leukemia (CLL) and acute myelogenous leukemia (AML) patients that only expressed B1 or SHCL-3, respectively. Furthermore, other malignant blood diseases, including malignant lymphomas, acute leukemias, and chronic leukemias disclosed no double marker positive cells. In a clinical setting, this assay was used for purifying HCs (by flow cytometry) from the peripheral blood from patients with no apparent morphological evidence of circulating HC infiltration and for monitoring the effect of interferon therapy. In conclusion, this assay should be of value for both diagnosis and monitoring patients with HCL.     

Membrane receptors and their redistribution in lymphoproliferative disorders.

Lymphoid cells from 20 patients with lymphoproliferative disorders, including chronic lymphocytic leukemia, hairy cell leukemia, Sezary syndrome, lymphoma, and lymphadenitis, were studied for redistribution of surface membrane immunoglobulins (SmIg) and concanavalin A (Con-A) receptors. Fluorescein-labeled polyvalent goat anti-human immunoglobulin and fluoresceinated concanavalin A were used as ligands. Results were similar with both ligands. The highest percentage of capping of ligand-membrane receptors was noted in mononuclear cells from patients with "hairy" cell leukemia: from 24% to 90%. These cells showed moderate to marked fluorescein activity and were able to cap within 15 min at 4 degrees C. Chronic lymphocytic leukemia cells showed a weak fluorescein stain with a very low percentage of cells (0%--16%) capping. Lymph node cells from patients with lymphoma demonstrated moderate to strong fluorescein activity with only an average of 3% of the cells capping; while lymphoid cells from patients with lymphaedenitis showed an average of 27.5% capping and moderate fluorescein activity. Capping of Con-A receptors in mononuclear cells from patients with Sezary syndrome was poor (0%--14%) with moderate fluorescein intensity. This report demonstrates difference in density and mobility of binding sites for SmIg and Con-A on the surface membrane of lymphoid cells from various subclasses of lymphoproliferative disorders. These differences may assist in the differential diagnosis and classification of these conditions.     

Acute vasculitis as a first manifestation of hairy cell leukemia

Hairy cell leukemia (HCL) is a lymphoproliferative malignancy characterized by bone marrow, spleen, liver, and occasionally lymph node infiltration with hairy cells, usually accompanied by splenomegaly and pancytopenia. We report an unusual case of HCL in a 53-year-old woman with leukopenia and sudden onset of fever of unknown origin, arthritis, and generalized maculopapular exanthem. Skin biopsy revealed perivascular and/or vessel wall lymphocytic infiltration in the dermis. On the basis of bone marrow biopsy and flow cytometry, the diagnosis of HCL was established. A detailed, retrospective re-evaluation of the skin biopsy helped to identify hairy cells among the cells of the perivascular infiltrations. Small-vessel vasculitis, as an atypical presentation, was found to predate a diagnosis of HCL. Recognition that vasculitis can reflect or antedate lymphoid malignancy may permit early diagnosis and aggressive treatment. A rapid response was obtained with a single course of cladribine.     

"Hairy cell" leukemia: a heterogeneous chronic lymphoproliferative disorder.

Thirteen patients with “hairy cell” leukemia and circulating tartrate-resistant acid phosphatase (TRAP)-positive mononuclear cells were studied. A high percentage of peripheral mononuclear cells from 12 patients were positive for surface membrane immunoglobulin (Smlg). Unlike studies in chronic lymphocytic leukemia, in most of these patients with “hairy cell” leukemia it was not possible to establish “clonality” on the basis of λ/κ or immunoglobulin-class cell surface markers because of frequent weak reactions with more than one antiserum in each group. Complement (C₃) receptor-bearing cells accounted for 69 per cent of the peripheral mononuclear cells in one patient. In another patient, 80 per cent of the peripheral mononuclear cells were positive for Fc receptors. Both patients also had high levels of Smlg-positive cells. In a third patient, peripheral mononuclear cells were of T-cell type as determined by over 80 per cent E rosetting and only 2 per cent Smlg-bearing cells. Phytohemagglutinin (PHA) stimulation on peripheral mononuclear cells from five patients revealed weak responses at three days. However, when this response was followed further, it reached normal intensity by five days of incubation, in contrast to cells from patients with chronic lymphocytic leukemia which gave a peak PHA response at eight to nine days. Cells from all patients, except cells from patients with T-cell type “hairy cell” leukemia, showed positive cytotoxic reactions with antiserums designating various B-cell (Merrit; la-like) alloantigenic groups. “Hairy-cell leukemia” appears to be a heterogeneous group of chronic lymphoproliferative disorders.     

The significance of paraproteinemia in hairy cell leukemia: case report and review of the literature

A case of hairy cell leukemia and IgG paraproteinemia is described. Peripheral blood surface marker analysis, serum paraprotein levels and immunoperoxidase stains of bone marrow sections at diagnosis and after 7 months of interferon treatment suggested the existence of two unrelated pathological B cell clones: one composed of malignant hairy cells and the other secreting the paraprotein. Previously reported cases of hairy cell leukemia with paraproteins are reviewed and our patient's contribution to the understanding of this association is stressed.     

CD11c (LEU-M5) expression characterizes a B-cell chronic lymphoproliferative disorder with features of both chronic lymphocytic leukemia and hairy cell leukemia.

Chronic lymphocytic leukemia (CLL) and hairy cell leukemia (HCL) are two common chronic lymphoproliferative disorders, each having characteristic clinical, morphologic, and immunologic features. Phenotypically, CD5 reactivity in CLL and CD11c (Leu-M5) reactivity in HCL have characterized these two leukemias among B-cell disorders. In this study, we report 14 cases of a novel chronic lymphoproliferative disorder characterized by lymphocytosis and CD11c expression, but morphologically similar to CLL. The patients' ages ranged from 46 to 81 years (median 62). Eleven had palpable splenomegaly, five with markedly enlarged spleens; only one patient had generalized lymphadenopathy. The white blood cell count ranged from 5.2 to 131.0 x 10(9)/L (median 20.8). The morphologic diagnosis in all cases was CLL, with the cells usually having abundant cytoplasm. No morphologic features, of hairy cells were evident; tartrate-resistant acid phosphatase cytochemistry was negative in all cases. Bone marrow biopsies were available in 8 of 14. Four showed focal nodular infiltrates and two had diffuse infiltrates similar to CLL; two showed only minimal interstitial involvement. All cases expressed multiple B-cell markers, and 12 of 14 had monoclonal surface immunoglobulin. The leukemic cells of all cases strongly expressed CD11c, while CD5 was expressed in 7 of 14; only 1 of the 14 cases expressed the lymph node homing receptor, Leu-8. This unique group of leukemias appears to represent the malignant transformation of lymphocytes arising from a stage of lymphocyte differentiation between that found in typical cases of CLL and that of HCL. CD11c is known to have an important function in cellular adhesion and may be important in determining the pattern of lymphocyte tissue distribution found in this group of patients.     

Relationship between hairy cell leukemia variant and splenic lymphoma with villous lymphocytes: Presentation of a new concept

An unusual case of low-grade B-cell lymphoproliferative disorder with peripheral lymphocytosis and splenomegaly followed for 4 1/2 years is reported. During this period, the phenotype of the tumor cells in the blood changed from that of hairy cell leukemia (HCL)/chronic lymphocytic leukemia (CLL) to HCL/prolymphocytic leukemia (PLL), to PLL. The lymphoid population in the blood showed a mixture of hairy cells, villous lymphocytes, small lymphocytes, and prolymphocytes, corresponding to the phenotypes at various stages. Although relatively specific markers for CLL, HCL, and PLL, such as CD5, CD11c, CD22, CD25, and FMC-7, were positive at various stages, all these markers have also been demonstrated in a large study series of splenic lymphoma with villous lymphocytes (SLVL). In addition, the histologic pattern of the bone marrow biopsy and splenectomy specimen were not typical for HCL. This case can therefore be classified either as HCL variant or as SLVL. As SLVL assumes various cytologic and histologic patterns, which overlap with different lymphoproliferative disorders, especially HCL variants, this entity appears to represent a heterogeneous group of lymphomas/leukemias that may evolve into each other. The absence of activation of c-myc and bcl-2 oncogenes as well as mutation of p53 tumor suppressor gene, together with the presence of only one single rearranged band for both heavy chain and κ light chain genes in our case suggest that these morphologically different lymphoid tumors may belong to the same family. © 1996 Wiley-Liss, Inc.     

Hairy cell leukemia: a review.

Hairy cell leukemia is a chronic but steadily progressive malignancy usually of older males. Clinically, patients present with splenomegaly and/or cytopenia. The diagnosis is made by demonstration of the hairy cell in Wright's-stained peripheral blood and in bone marrow and by the characteristic histologic findings in the bone marrow biopsy and spleen sections. Infection is the most significant problem complicating the course of patients with hairy cell leukemia and the role of granulocytopenia and/or monocytopenia is undoubtedly substantial. Splenectomy has produced an objective response in improving hematologic parameters in a large number of patients and may prolong survival in those patients who respond. The precise nature of hairy cells remains unknown. The cells exhibit features of both monocytes and B-lymphocytes in morphologic, cytochemical, immunologic and functional studies. A more complete understanding of the monocytic and lymphocytic stem cells and their maturation may provide insight into the origin of the hairy cell.     

Analysis of human myelogenous leukemia cells in the fluorescence- activated cell sorter using a tumor-specific antiserum

The properties of a rabbit antiserum (anti-AML) raised to a purified protein from membranes of human acute myelogenous leukemia (AML) cells is described. Bone marrow and peripheral blood leukocytes (PBL) from either normal individuals or patients with either myeloproliferative or other disorders were analyzed in a fluorescence-activated cell sorter (FACS IV) after labeling with anti-AML, normal rabbit serum (NRS), or antiserum raised to normal human membrane antigens. Of 40 cell samples from patients with acute myelogenous leukemia, 39 reacted strongly with the anti-AML antiserum. Similarly, all of 19 specimens from patients with chronic granulocytic leukemia reacted with the anti-AML. When 42 bone marrow or PBL samples from patients with a variety of lymphoproliferative disorders were examined, 2 specimens reacted with the antiserum, both from individuals with diagnoses of acute lymphocytic leukemia (ALL). None of the 14 normal bone marrow or PBL donor specimens tested reacted with the antiserum. It was also found that essentially all samples from patients in clinical remission from AML had high numbers of cells reactive with the anti-AML. When cells from such individuals were labeled and sorted on the FACS IV, it was found that cells fluorescing strongly with the anti-AML contained cells of both myeloid and lymphoid origin. The implications of these results are discussed.     

CD5-Negative,CD10-Negative small B-cell leukemia: Variant of chronic lymphocytic leukemia or a distinct entity?

CD5- and CD10-negative chronic lymphocytic leukemias are quite uncommon as compared to the CD5-positive CLL. We reviewed 250 sequential cases of peripheral blood lymphocytosis to characterize cases of small B-cell lymphoproliferative disorders, submitted with a clinical diagnosis of chronic lymphocytic leukemia exhibiting a non-classic immunophenotypic profile. Six cases of CD5-, CD10-negative chronic lymphocytic leukemias and no tissue involvement were identified that revealed high-density surface-membrane immunoglobulin and CD20 expression, with variable expression of CD11c, CD23, and CD25. Most had a profound leukocytosis (mean WBC 180 x 10(9)/L) with proliferation of mature-appearing lymphocytes. Subsequent bone marrow biopsies showed diffuse infiltration by neoplastic cells in all evaluated patients. The clinical course appeared indolent, with follow-up revealing three patients alive (survival time 38-68 months), while two died of unrelated causes and one was lost to follow-up soon after diagnosis. These cases may represent somewhat unusual chronic lymphoproliferative disorders, with morphologic features and immunophenotypic profile not readily classifiable, but which are certainly atypical for classic chronic lymphocytic leukemia. Some of these features are reminiscent of those seen in marginal-zone lymphoma. However, it is most unusual for this known to be tissue-based disease to present primarily as leukemia rather than lymphoma.     

Hairy cell leukemia: diagnosis and management

Long-term follow-up of 18 patients with hairy cell leukemia seen at a single institution is reported: diagnostic and therapeutic modalities are described. Although the clinical features of this disease are homogeneous, it is frequently misdiagnosed initially. Bone marrow biopsy was diagnostic in all 17 patients studied prior to splenectomy. The presence of circulating "hairy" cells is greatly variable. The cause of pancytopenia is unclear: splenic sequestration was not demonstrated by 51Cr red cell studies in three of four patients. In most patients, splenectomy resulted in amelioration of pancytopenia. No clinical features prior to splenectomy could predict response to surgery. The results of chemotherapy and splenic irradiation were variable and unpredictable. Although bone marrow infiltration persists following splenectomy, this remains the only established therapy in hairy cell leukemia and is usually followed by long, uncomplicated survival.     

Hairy cell leukemia variant: a morphologic, immunologic and clinical study of 7 cases

Hairy cell leukemia (HCL), a well-recognized chronic lymphoproliferative disorder, is frequently characterized by pancytopenia, monocytopenia, splenomegaly and marrow fibrosis, which typically leads to an unsuccessful bone marrow aspiration (dry tap). Patients with a high white cell count without neutropenia and/or monocytopenia, with an aspirable and hypercellular marrow, splenomegaly and neoplastic cells with hairy cell features have been recently recognized and classified as HCL variants. We report here the clinical, hematological and immunological features of 7 such cases. All patients presented splenomegaly with a high leukocyte count; 2 were anemic and only 1 thrombocytopenic. Five patients were treated with alpha-Interferon (alpha-IFN) but 4 failed to achieve any significant response; two of these were subsequently splenectomized and successfully treated with Chlorambucil. Splenectomy, followed by Chlorambucil, was performed at diagnosis in the remaining 2 cases, both of which achieved a partial response and are alive and well. Six out of the 7 patients are still alive. The recognition of these peculiar patients is also important because they most often do not respond to alpha-IFN, while splenectomy, followed by Chlorambucil, may be a reasonable therapeutic option for them.     

Peripheral blood remission of hairy cell leukemia after transfusion hepatitis

Hairy cell leukemia is a chronic lymphoproliferative disorder characterized clinically by splenomegaly and cytopenias. Spontaneous remissions are rare and splenectomy is often performed when the blood counts worsen and cause symptoms. Three of our patients with hairy cell leukemia developed recurrent pancytopenia and transfusion-dependent anemia after splenectomy. Each subsequently acquired transfusion hepatitis and in two patients marked hematologic improvement was noted within 2 months. Complete peripheral blood remission occurred within 17 months in all patients although bone marrow infiltration with hairy cells persisted. One patient remains in remission for 12 years; the other two succumbed to infectious illnesses but with normal blood counts. The mechanism by which hepatitis virus induces hematologic recovery in patients with hairy cell leukemia is unknown but may involve augmentation of the interferon system.     

Flow cytometric immunophenotyping is of great value to diagnosis of natural killer cell neoplasms involving bone marrow and peripheral blood

Natural killer (NK) cell neoplasms are unusual disorders. In this study we compared results of flow cytometric immunophenotype (FCI) with cytomorphology, histopathology and clinical findings in a series of patients with NK cell neoplasms with peripheral blood and/or bone marrow involvement, and the FCI of neoplastic and normal NK cells were compared. Retrospective data and specimens (bone marrow aspiration or peripheral blood) from 71 cases of NK cell neoplasms were obtained. All patients have been demonstrated laboratory and clinical features consistent with NK cell neoplasms, and the subtypes were determined by integrated clinical estimation. Routine 4-color flow cytometry (FCM) using a NK/T cell related antibody panels was performed. NK cell neoplasms were divided into two major subtypes by FCI, namely malignant NK cell lymphoma, including extranodal nasal type NK cell lymphoma (ENKL, 11 cases) and aggressive NK cell lymphoma/leukemia (ANKL, 43 cases), and relative indolent chronic lymphoproliferative disorder of NK cell (CLPD-NK, 17 cases). The former exhibited stronger CD56-expressing, larger forward scatter (FSC) and more usually CD7- and CD16-missing. FCI of CLPD-NK was similar to normal NK cells, but CD56-expressing was abnormal, which was negative in five cases and partially or dimly expressed in eight cases. Cytomorphologic abnormal cells were found on bone marrow slides of 4 cases of ENKL and 30 cases of ANKL. Eight cases of ENKL were positive in bone marrow biopsies, and other three cases were negative. In 32 cases of ANKL which bone marrow biopsies were applied, 21 cases were positive in the first biopsies. Lymphocytosis was found only in six cases of CLPD-NK by cytomorphology, and biopsy pathology was not much useful for diagnosing CLPD-NK. These results suggest that FCM analysis of bone marrow and peripheral blood was superior to cytomorphology, bone marrow biopsy, and immunohistochemistry in sensitivity and early diagnosis for ANKL, stage III/IV ENKL and CLPD-NK. FCI could not only define abnormal NK cells but also determine the malignant classification. It is beneficial for clinical management and further study of NK cell neoplasms.     

Evaluation of trisomy 12 by fluorescence in situ hybridization in peripheral blood, bone marrow and lymph nodes of patients with B-cell chronic lymphocytic leukemia

BACKGROUND AND OBJECTIVE: Trisomy 12 is the most common numerical chromosomal aberration in patients with B-cell chronic lymphocytic leukemia (B-CLL). Fluorescence in situ hybridization (FISH) has improved the detection of this cytogenetic abnormality and has made detection possible in all phases of the cell cycle. The presence of the trisomy 12 positive (+12) cell population has generally been investigated in leukemic cells obtained from the peripheral blood of CLL patients. To ascertain whether trisomy 12 is expressed homogeneously in cells of different hemopoietic tissues, we applied FISH to lymph node, peripheral blood and bone marrow samples obtained simultaneously from 23 untreated B-CLL patients. DESIGN AND METHODS: Twenty-three newly diagnosed patients with B-CLL, 15 in stage B and 8 in stage C, were included in the present study. Peripheral blood smears, bone marrow aspirate smears and lymph node touch imprints were collected from each patient at diagnosis. Cytologic preparations were examined by light microscopy in order to assess the lymphocyte morphology. Immunophenotyping was performed by cytofluorimetric analysis of the peripheral blood, bone marrow and lymph node mononuclear cell suspensions. The diagnosis was supported in all cases by histologic findings in bone marrow biopsy and lymph node biopsy specimens. Fluorescence in situ hybridization was performed on smears of blood and aspirated bone-marrow and lymph node touch imprints obtained by fresh tissue apposition. RESULTS: In 6 of the 23 cases (26%) trisomy 12 was clearly present in all tissues examined. A comparative analysis of the three different hemopoietic tissues was performed. A higher percentage of leukemic CD5+CD23+ cells was detected in lymph nodes than in peripheral blood and bone marrow. A significantly higher proportion of trisomic cells was observed in lymph nodes samples than in peripheral blood or bone marrow smears of trisomy 12 positive CLL patients. INTERPRETATION AND CONCLUSIONS: Several previous reports show that only a proportion of malignant B-CLL cells carry trisomy 12 when analyzed by interphase FISH. The higher proportion of +12 cells in lymph nodes than in peripheral blood or bone marrow of CLL patients with trisomy 12 could reflect different cell distributions in different tissues, or lymph node specific tropism, or proliferative advantage in selected tissue. At present, the role of trisomy 12 in the pathogenesis of lymphoproliferative disorders is unclear.     

电镜观察骨髓有核细胞对非霍奇金淋巴瘤的诊断价值

目的总结透射电子显微镜观察骨髓有核细胞形态结构对非霍奇金淋巴瘤(NHL)诊断和鉴别诊断的作用。方法电镜观察骨髓有核细胞形态结构,根据中幼稚细胞种类和分化程度对患者进行诊断,回顾分析48例NHL患者的电镜和临床诊断符合率。结果48例患者中,电镜发现41例患者骨髓液中存在幼稚淋巴细胞(85.4%),21例电镜诊断NHL,9例提示急性淋巴细胞白血病(ALL),2例提示毛细胞白血病(HCL),2例提示慢性淋巴细胞白血病(CLL),1例浆细胞白血病(PL),6例淋系增殖疾病(LPD)未进行分类。7例患者电镜观察未发现或明确幼稚淋巴细胞,1例提示急性髓系白血病(AML),2例描述发现异常细胞,但未定性,2例提示病态造血;2例无提示。48例NHL患者中,发现病态造血28例。结论电子显微镜观察骨髓有核细胞对NHL、尤其是原发部位不明的NHL具有重要诊断价值。其次,电镜能够评价NHL诱导的骨髓病理反应。     

Expression and function of a receptor for hyaluronan-mediated motility on normal and malignant B lymphocytes

Migration through extracellular matrix is fundamental to malignant invasion. A receptor for hyaluronan-mediated motility (RHAMM) has previously been shown to play a fundamental role in locomotion of ras- transformed cells as well as functioning in signal transduction. Expression of RHAMM was characterized on B lymphocytes from normal and malignant lymphoid tissues using multiparameter phenotypic immunofluorescence analysis as well as functional analysis of its role in locomotion of malignant hairy cell leukemia B cells. RHAMM is not detectable on most normal B cells located in blood, spleen, or lymph node, but it is detectable on bone marrow and thymic B cells. Among B- cell malignancies, it is expressed on most terminally differentiated B cells from multiple myeloma bone marrows, is present on a subset of non- Hodgkin's lymphomas, and is absent on B chronic lymphocytic leukemia. Activation of peripheral blood B cells by Staphylococcus A cowan (SAC), but not by pokeweed mitogen, induced transient expression of RHAMM at day 3 of culture, suggesting RHAMM may be used by antigen-activated normal B cells. For malignant cells, expression of RHAMM increased on long-term culture of bone marrow plasma cells from multiple myeloma patients, indicating prolonged expression in contrast to the transient expression on SAC-activated normal B cells. Intriguingly, RHAMM was expressed on hairy leukemia cells located in spleen but absent from those in peripheral blood of the same patient. RHAMM, as expressed on splenic hairy cells, was a 58-Kd molecule that binds hyaluronan, is encoded by a 5.2-kb messenger RNA, and participates in locomotion by these cells. Hairy cells locomoted in response to hyaluronan at 4 mu per minute. Monoclonal antibody to RHAMM inhibited this locomotion almost completely as detected using video time-lapse cinemicrography. These observations are consistent with a role for RHAMM in malignant invasion and metastatic growth.     

Monoclonal antibodies against the chronic lymphatic leukemia antigen cCLLa: characterization and reactivity

Monoclonal antibodies (MoAbs) were developed against the cCLLa, a 69-kilodalton leukemia-associated antigen expressed on malignant cells of B-type chronic lymphatic leukemia (B-CLL) and its variants: prolymphocytic (PLL) and hairy cell leukemias (HCL). Two hybridomas yielded approximately 2 and approximately 7.5 mg/mL of IgG2a kappa and IgM kappa, respectively. Monoclonal surface immunoglobulin-bearing cells of all B-CLL patients studied (n = 30) reacted with the MoAbs (r greater than .99) regardless of stage or lymphocyte count. This suggests that the malignant clone in CLL can be identified and its size monitored by using our MoAbs. In contrast, normal B lymphocytes, a large panel of normal, reactive and neoplastic cells, and malignant cell lines failed to react with either MoAb as judged by indirect immunofluorescence and by flow cytometry. Only two patients (one with non-Hodgkin's lymphoma, the other with acute myeloblastic leukemia) exhibited a small cell subset reactive with the MoAbs. cCLLa specificity was suggested by selective target cell reactivity and competitive inhibition-absorption and confirmed by immunoprecipitation. MoAbs IgG2a kappa and IgM kappa appeared to share antigenic determinants and were moderate and avid complement binders inducing 100% and 40% target cell lysis, respectively. cCLLa density on malignant CLL and HCL cells was estimated by equilibrium binding studies using the IgG2a kappa MoAb at 1.7 and 9 X 10(6)/cell, respectively. The restricted expression of the cCLLa and the specificity and cytolytic activity of the anti-cCLLa MoAbs support these antibodies as probes for the classification of lymphoproliferative diseases and for the specific diagnosis and treatment of B-CLL and its variants.