Subsets of hairy cell leukemia defined by unique membrane proteins

Decreased expression of Ii-derived p25 and of P67/69 in hairy leukemic cells

Hairy leukemic cells had altered expressions of accessory proteins (Ii, Ip, p70, p25) which associated intracellularly with class II MHC molecules. Immunoprecipitates from [35S]methionine, pulse-chase labeled leukemic cells, B-lymphoblastoid cells, and Burkitt's lymphoma cells were examined after 2-dimensional, polyacrylamide gel electrophoresis. The class II MHC-associated Ii chain was present in all three cell types, but the Ii-derived p25 protein was not found in HCL cells. Ip, the sialic acid-derivatized form of Ii, was well expressed in BLCL and Raji cells, but weakly in HCL cells. P70 was strongly expressed in BLCL and Raji cells, but negligibly in HCL cells. These alterations might reflect deficient mechanisms for antigen processing and presentation by these leukemic cells.

Hairy leukemic cells which hyperexpress Ii do not demonstrate Ii genome alterations by restriction endonuclease analysis

The finding of increased expression and apparently altered processing of Ii in hairy leukemic cells led us to test for Ii genomic alteration by Southern-type Ii cDNA hybridization to leukemic spleen DNA cleaved with a series of restriction endonucleases. Some insertions, deletions, or point mutations, potentially detectable by this technique, might correlate to alteration in expression and function of Ii (and indirectly, class II antigens). No changes in genomic structure of Ii were detected in DNA isolated from spleens of five patients with hairy cell leukemia, compared with DNA preparations from peripheral blood cells of nineteen healthy blood donors. These experiments were consistent with the view that gross structural alteration of the Ii genome had not occurred in hairy leukemic cells.

Hairy cell leukemia

Hairy cell leukemia is a chronic lymphoproliferative disorder that has been recognized as a separate clinical pathologic entity for the last 25 years. After a decade of discussions about the origin of the neoplastic cell, it has now been well established that hairy cells represent a certain, rather mature stage of B-cell differentiation. Evidence for this has been derived from studies using immunophenotyping with monoclonal and polyclonal antibodies, cytochemistry, and immunoglobulin gene rearrangement. For many years, splenectomy was the only therapy of proven value in hairy cell leukemia. For patients who showed insufficient response to the operation, chemotherapy with low-dose alkylating agents was moderately successful, whereas polychemotherapy often resulted in excessive toxicity. More recently, therapy with alpha-interferon has been shown to be very promising, whereas deoxycoformicin may be an attractive alternative. These new advances in immunology and therapy are reviewed.

RAB-1: a new monoclonal antibody to leukemic hairy cells

RAB-1, a new monoclonal antibody (McAb) to human leukemic hairy cell (HC) was produced. Using indirect immunofluorescence methods and microscopic or flow cytometric analysis, it was found that the RAB-1 antigen was expressed on few resting B cells and not on resting T lymphocytes, platelets, monocytes, erythroid and myeloid cells. RAB-1 expression on malignant cells was as follows: strongly positive in 15/15 hairy cell leukemia (HCL), negative with non-T and T-acute lymphoblastic leukemia and T-chronic lymphocytic leukemia (CLL); weakly expressed on myeloma and Waldenstrom cells; moderately on 10-25% of the cells in 4/10 B-CLL and 6/10 B lymphomas and in 7/7 B-prolymphocytic leukemia (PLL). Amongst human cell lines that were tested, RAB-1 reacted strongly with one HC line, moderately with the EBV-lymphoblastoid Daudi and Raji Burkitt's lines and was not expressed on Ramos, ALL, myeloid and erythroid cell lines. Normal B cells activated with PWM or anti-mu beads, and malignant B cells activated with anti-mu and TPA did not show an increase of expression of RAB-1 antigen. Interestingly, 30-40% of T4-Class II antigen positive cloned cells and T cells activated with PHA and Con.A expressed RAB-1, suggesting that this McAb recognizes surface molecule, newly induced during T-cell activation and constitutively expressed on HC and some B-cell malignancies.

Expression of p35 in hairy leukemic cells from Japanese patients

Spiro and coworkers found a 35000 dalton membrane protein (p35) expressed abundantly in hairy cells of a subset of white, American patients with hairy cell leukemia. They subsequently identified p35 to be the human homologue of murine Ii, an electrophoretically invariant protein associated with Ia molecules. Using related analytical techniques, we have studied leukemic cells of two blood and one splenic samples from three Japanese patients with hairy cell leukemia and have demonstrated abundance of p35 in the splenic and one of the blood samples. The second blood sample was negative for p35 by our method of analysis, but the same hairy cells became positive for p35 at 2 months in culture and negative again at 4 months in culture. All 3 samples of this patient (fresh hairy cells and cultured cells at 2 and 4 months) remained consistently positive for Ia and for light chain-restricted immunoglobulin. Control cells from one each of acute lymphoblastic leukemia and Burkitt's lymphoma were negative for abundant p35 expression after culture as well as in the fresh state. One can conclude that the Japanese form of hairy cell leukemia, while varying in several distinct clinical and laboratory features from hairy cell leukemia in caucasians, is characterized also by abundant expression of p35 as seen in a subset of white patients. In addition, this expression of p35 is developed by hairy leukemic cells in culture initially but is lost upon longer term culture, in parallel with the level of tartrate-resistant acid phosphatase reactivity.

Differential effect of TPA and n-butyrate on induction of Ii and EBV antigens in the P3HR-1 lymphoblastoid cell line

The aim of this study was to test whether EBV induction by TPA or n-butyrate was related directly to hyperexpression of Ii, an electrophoretically invariant, 35 000 dalton, HLA-DR antigen-associated glycoprotein which is abundantly detected in EBV freshly transformed cells and is enhanced by EBV superinfection of lymphoblastoid cell lines. P3HR-1 lymphoblasts were treated with n-butyrate or TPA in variable doses and durations. The augmented expression of Ii, EBV antigens (EA and VCA), DNA synthesis, and cell growth and viability were monitored. n-Butyrate induced hyperexpression of Ii at 2 days with a maximal effective dose of 4 mM, induced EBV antigens (EA and VCA) in 36 per cent of the cells at 2 days, inhibited DNA synthesis and cell growth, and was not cytolytic at 48 h when Ii induction was maximal. TPA did not induce hyperexpression of Ii, induced EBV antigens (EA) in 30 per cent of the cells at 4 days, did not inhibit DNA synthesis and cell growth, and was not cytolytic in the time course and doses studied. Ii expression, therefore, did not appear to be an obligatory consequence of EBV antigen induction. Ii induction might be related to an effect of EBV inducers on cellular DNA synthesis, or on control of the cell cycle, or directly upon Ii gene regulation.

Enhanced Ii expression after n-butyrate treatment of a P3HR-1 Burkitt's lymphoma subline which does not express HLA-D

Treatment of P3HR-1 Burkitt's lymphoma cultured cells with 4 mM n-butyrate for 48 h induced the abundant expression of a 35 000 dalton, microsomal membrane protein which was demonstrated to be the electrophoretically invariant Ii molecule. To prove this point, [35S]methionine-labelled, microsomal membrane proteins or immunoprecipitates of such detergent-solubilized proteins were subjected to electrophoresis either in SDS gels or in two-dimensional, nonequilibrium pH gradient gels. The induced p35 molecule was judged to be Ii by molecular weight and isoelectric characteristics and by immune complex associations. The abundant expression of Ii on butyrate-treated P3HR-1 cells mimicked the high level of expression of p35 or Ii on leukemic cells of a subset of patients with hairy cell leukemia. Alpha and beta chains of the HLA-D complex were absent from the P3HR-1 cell line and present in the Jijoye parent from which mutant P3HR-1 was derived. This relatively simple model can lead to the study of inducible synthesis, processing and expression of Ii, with or without HLA-D alpha and beta chains.

Demonstration of p35 in hairy cell leukemia of Japanese patients

Using SDS polyacrylamide gel electrophoresis (SDS-PAGE), several coworkers isolated a unique membrane protein that they named p35 from hairy cells of white patients with hairy cell leukemia. In the current study using a similar technique, p35 was identified in hairy cells from 2 of 4 Japanese patients with hairy cell leukemia. Further, p35 was immunoprecipitated from the leukemic membrane proteins of one of these two Japanese patients with an anti-hairy cell serum prepared against hairy cells of a typical white patient. Because both Japanese and white patients share the unique membrane antigen, it is proposed that the Japanese have the hairy cell leukemia as whites despite some differences in laboratory features.

Identification of hairy cell leukemia subset defining p35 as the human homologue of Ii

A molecule defining a subset of patients with hairy cell leukemia (HCL) on the basis of being abundantly labeled with [35S]methionine, was demonstrated to be the human homologue of murine Ii, a glycoprotein which lacks alloantigenic variation and is associated non-covalently with Ia antigens. In one-dimensional SDS-polyacrylamide gradient gel electrophoresis, the HCL-subset-defining molecule migrated with HLA-DR molecules which were immunoprecipitated with a specific heteroantiserum. These molecules were further defined in two-dimensional, SDS and non-equilibrium pH gradient electrophoresis of either membrane preparations or immunoprecipitates formed with various antibodies. [35S]methionine-labeling of the HCL-subset-defining molecule was greater in hairy leukemic cells than in lymphoblastoid cell lines. The subset-defining species was associated non-covalently with HLA-DR alpha and beta chains and ran electrophoretically at a position described for murine and human Ii molecules (in terms of pI and weight). Metabolic labeling of HLA-A,-B and -DR was also increased in HCL cells relative to lymphoblastoid cell lines. A separate protein, of 41,000 mol. wt and pI of 7-8, resembled another Ii-associated molecule which has been described in murine and human studies.

Restrictions upon Epstein-Barr virus infection of the leukemic cell are demonstrated in patients with hairy cell leukemia

We tested the hypothesis that Epstein-Barr virus (EBV) might actually infect leukemic hairy cells in vivo by examining those cells for the EBV-receptor, EBV nuclear antigen (EBNA) and membrane antigen (MA), for spontaneous transformation and rescue of infectious virus and for presence of EBV genome. EBV-receptors were found on subpopulations of leukemic cells from each of 7 patients with hairy cell leukemia (HCL) tested. MA was present on low numbers (1-5 per cent) of fresh leukemic cells of 7 patients and in some instances occurred with a greater frequency after 3 to 5 days in culture, with or without 12-O-tetradecanoylphorbol-13-acetate. In 11 fresh leukemic cell preparations from 8 HCL patients, no EBNA was demonstrated. However, 2 samples after 4 days in culture expressed low frequencies of EBNA-positive cells. Spontaneous, EBV-positive cell lines were established with a high transformation efficiency from 3 HCL blood samples but not from 8 other specimens. Infectious EBV could be rescued from some hairy leukemic cell preparations by co-cultivation with cord blood lymphocytes. These results demonstrated that leukemic cell populations harbored infectious EBV, that the leukemic cells expressed virus receptors and suggested that a small subpopulation of leukemic cells might become infected in vivo at least transiently and possibly transformed in vitro by EBV. To test for the extent of occult in vivo infection of leukemic cells with EBV, Southern type hybridization studies were performed with a probe for EBV genome (Bam HI W). At a sensitivity level of 0.1 genome per cell, EBV genome was not detected in the leukemic cell populations of 7 patients. We conclude that host defence mechanisms protecting these individuals from EBV also prevent infections of the leukemic cell and/or most hairy leukemic cells are not suitable targets for both infection and transformation.

Surface glycoprotein patterns of B type chronic lymphocytic leukaemia cells correlate with the clinical activity of the disease

The surface glycoprotein patterns of leukaemic B lymphocytes from 20 patients with clinically progressive or non-progressive chronic lymphocytic leukaemia (CLL) were investigated. Cells were labelled by the neuraminidase-galactose oxidase-tritiated sodium borohydride technique and the radioactive proteins were separated by polyacrylamide slab gel electrophoresis and visualized by fluorography. A total of 13 to 16 bands were detected. A common surface glycoprotein pattern for CLL cells was seen in all patients consisting of 7 proteins with the apparent molecular weights of 210, 200, 185, 150, 135, 110 and 90 kilodaltons, respectively. Interesting differences were, however, observed as cells from patients with progressive CLL in general lacked the glycoproteins 120, 72 and 67 K, which were found on cells from inactive CLL. The possible biological and clinical significance of these findings is discussed.

Monoclonal antibodies with specificity for hairy cell leukemia cells

Hairy cell leukemia is a well described clinical entity, but the cell of origin for this leukemic cell and its function are still unknown. There are no totally specific markers for this cell, although tartrate-resistant acid phosphatase staining has been used extensively as a diagnostic test. This study describes three monoclonal murine antibodies with variable specificity for hairy cells. Antibody 1 was highly specific for hairy cells and was not found to react with normal or leukemic cells in this limited study. It did not react with the cells of all patients. It also did not react with all of the hairy cells of some of the positive cases. Antibodies 2 and 3 reacted with virtually all hairy cells but not with normal peripheral blood cells. However, reactions were obtained with certain leukemic myelomonoblasts and some activated B cells. The most obvious use for these three antibodies is for diagnostic purposes. They should also be helpful reagents to investigate the origin of the leukemic hairy cell. The possibility that antibody 1 detects a tumor-specific antigen is discussed.

Differences in synthesis of membrane proteins by leukemic cells from spleen and peripheral blood indicate distinct subsets of malignant cells in a patient with prolymphocytic leukemia

Morphological and biochemical differences were demonstrated between prolymphocytic leukemia cells obtained from the spleen and peripheral blood of one patient. Peripheral blood prolymphocytes had consistently smaller nuclear-cytoplasmic ratios than did splenic prolymphocytes. Percoll gradient-purified prolymphocytes from the spleen synthesized abundant amounts of some membrane proteins which were hardly expressed by peripheral blood prolymphocytes. Peripheral blood prolymphocytes did not change their expression of membrane proteins during three days in culture. These findings are consistent with the view that prolymphocytic leukemia cells from the spleen exist, on the average, at an earlier stage of differentiation than do circulating leukemic cells, and that peripheral blood leukemic cells are frozen at a specific phase of differentiation.

Antibodies to Epstein-Barr virus-specific antigens in patients with hairy-cell leukemia

Antibody titers to Epstein-Barr virus (EBV)-specific antigens of 19 patients with hairy-cell leukemia (HCL) were markedly elevated. All patients showed high titers of IgG anti-viral capsid antigen (VCA) reactivity equal to or greater than 320 (reciprocal titer). The anti-VCA reciprocal geometric mean titer (GTM) was 1106 in contrast to a GMT of 80 for healthy controls (p less than 0.001). No IgM anti-VCA antibody was detected, but three patients had IgA anti-VCA antibodies. Fourteen patients had elevated anti-early antigen (EA) titers (GMT = 177) which were indicative of active infections with EBV. Seven of the 14 patients demonstrated the diffuse component antibody of the early antigen (EA) complex at a GMT of 98. Anti-Epstein-Barr virus nuclear antigen (EBNA) was detected in sera of 16 patients (GMT = 64, controls GMT = 79). It is noteworthy that three patients with anti-VCA titers lacked anti-EBNA titers. These anti-body responses suggest that immunodeficiency secondary to HCL allowed reactivation of the virus.