Normal equivalent cells of B cell malignancies: analysis with monoclonal antibodies

Alkaline Phosphatase and Gamma Glutamyltranspeptidase in Human Lymphomas

Alkaline phosphatase (AP) and gamma glutamyltranspeptidase (GGT) were studied in normal lymphoid cells and in 28 cases of human lymphomas (23 of non-Hodgkin's and 5 of Hodgkin's disease). The expression of AP was enhanced in several samples with a high proportion of mature B cells, particularly in centroblastic-centrocytic lymphoma, whereas tissues mainly composed of T cells always showed low levels of this enzyme. GGT levels were high in thymus, as well as in centroblastic-centrocytic lymphoma and other NHL, thus demonstrating no restriction to a particular cell lineage. Some B-cell neoplasms with cellular origin different from that of centroblastic-centrocytic lymphoma, such as chronic lymphocytic leukemia and centrocytic lymphoma, had low levels of both enzymes. The role of investigation with specific antibodies against these two enzymatic activities in the physiology of lymphoma cell membrane is discussed.

Immunotherapies targeting CD38 in Multiple Myeloma

Recently, the monoclonal antibody daratumumab was approved as a single agent for the treatment of patients with relapsed/refractory Multiple Myeloma (MM). Daratumumab is an antibody targeting surface molecule CD38 on myeloma cells and the agent is already widely being used based on its good tolerability and proven efficacy. We believe, however, that the efficacy of this drug and other anti-CD38 monoclonal antibodies can be further improved by combining it with other types of immunotherapies. Furthermore, surface molecule CD38 can be used as a target for immunotherapies other than just naked monoclonal antibodies. In this report, we review the expression pattern of CD38 among normal tissues and in different types of plasma cell dyscrasias including their progenitor cells, minimal residual disease, and circulating tumor cells. We summarize the physiological role of CD38 as well as its role in the pathophysiology of MM and we present the most recent clinical trials using CD38 as a target. In addition, we highlight possible combination immunotherapies incorporating anti-CD38 monoclonal antibodies and we demonstrate alternative immunotherapeutic approaches targeting the same antigen such as CD38-specific chimeric antigen receptor (CAR) T cells.

Plasma cell leukemia: a report on 15 patients

Plasma cell leukemia (PCL) can be considered the leukemic variant of multiple myeloma. The diagnosis is based on hematological features, including a plasmacytosis exceeding 2 x 10(9)/l and any evidence of a clonal plasma cell proliferation. There are two forms of PCL: the primary form occurring in individuals without preceding multiple myeloma, and the secondary form arising as a late manifestation in patients with multiple myeloma. From 1974 to 1988 we diagnosed 8 primary PCL cases out of a total 301 multiple myeloma cases (incidence, 2.6%) and a total of 847 acute leukemia cases (incidence, 0.9%). During the same period we observed in 7 multiple myeloma patients a terminal PCL, for an incidence of PCL in myeloma of 2.3%. Most clinical characteristics were similar in both types of plasma cell leukemia. In particular we found no difference in the average age and in the incidence of bone pain, hepatosplenomegaly, lytic bone lesions. None of our cases showed a clinically relevant lymphadenopathy either as presenting symptom or during the course of the disease. The values for hemoglobin, leukocytes, plasma cells, serum creatinine and calcium did not differ significantly between the two groups of patients. The median survival was 7 months for patients with primary PCL and 1 month for patients with secondary PCL. 5 of the 8 patients with primary PCL obtained a response to conventional myeloma therapy including single alkylating agents, with a duration ranging from 7 to 44 months. Only 1 of the patients with secondary PCL had a partial response after combination chemotherapy.

Novel insights in chronic lymphocytic leukemia: are we getting closer to understanding the pathogenesis of the disease?

Chronic lymphocytic leukemia (CLL) has unique epidemiologic, biologic, and clinical features. The progressively emerging picture leads us to consider that the critical genes for malignant CLL cells are those regulated by a number of microRNAs revealed by refined cytogenetic and molecular studies, and that the key molecule is the B-cell receptor (BCR). The hypothesis that CLL cells might be selected by some sort of antigenic pressure is strengthened by numerous findings indicating that a BCR-mediated stimulation plays a relevant role in the natural history of the disease and that autoantigens, as well as molecular structures instrumental in eliminating and scavenging apoptotic cells and pathogenic bacteria, may be relevant in triggering and/or facilitating the evolution of CLL. An important question is whether the tiny monoclonal B-cell populations phenotypically similar to CLL (that occur in the peripheral blood of about 3.5% of healthy individuals and are termed monoclonal B lymphocytosis) might be a critical step in the development of CLL. All relevant events of CLL occur in tissues in which a number of cellular and molecular interactions shape a microenvironment conducive to the accumulation of malignant cells and favor the organization of proliferating cells in focal aggregates of variable size that form the pseudofollicular proliferation centers. Given the impact that understanding the pathogenesis of CLL might have on the development of new treatments, the purposes of this review are to discuss whether the novel insights in CLL are leading us closer to understanding the tenet of the disease; to define the emerging new, stimulating questions; and to unfold the major challenges that still need to be addressed.

From normal to clonal B cells: Chronic lymphocytic leukemia (CLL) at the crossroad between neoplasia and autoimmunity

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy endowed with a number of features that recall autoimmune disorders, including the CD5 expression and the development of autoimmune manifestations restricted to self antigens expressed by hematopoietic cells. Several evidences strongly support the possibility that an antigenic stimulation through the B-cell receptor (BCR) is involved in the selection and possibly also the expansion of the malignant clone. Though all evidences suggest specific Ag recognition and possibly stimulation at different time-points, the nature of the Ag(s) is still unknown. It appears likely that CLL cells derive from a pool of auto/polyreactive CD5(+) B cells. Hence CLL appears to be a B-cell malignancy triggered or facilitated in its development and evolution by an auto-Ag. The crucial issues have become to what extent this deleterious binding capacity is central to the natural history of the disease and how it relates to the malignant transformation of the cell.

lmmunoelectron microscopic examination of cord blood CD5+ B cells

In this study, we have categorized cord blood CD5(+) B cells, which were examined using the horseradish peroxidase-colloidal gold double labeling immunoelectron microscopy, into three subtypes based on their morphology and immunohistochemical characteristics. Type 1a cells and type 1b cells (9% and 17% of the CD5(+) B cells, respectively) had few cytoplasmic organelles, a high nuclear/cytoplasmic (N/C) ratio (0.66 +/- 0.03 and 0.58 +/- 0.04, respectively), and a low nuclear contour index (NCI) value (1.56 +/- 0.30 and 1.50 +/- 0.27, respectively), whereas type 2 cells (74% of the CD5(+) B cells) had a low N/C ratio (0.44 +/- 0.11) and a high NCI value (2.05 +/- 0.68). Type 2 cells, which had many cytoplasmic organelles, frequently had several uropod-like processes that bound to the gold particles. The N/C ratios clearly showed that there were significant differences among the three types of CD5(+) B cells (p < 0.01), and between CD5(+) T cells and the three types of CD5(+) B cells (p < 0.05). For the NCI values, only type 1b and type 2 cells showed a significant difference (p < 0.05). These findings suggest that type 1a cells are transformed into type 1b cells, and then into type 2 cells.

Both splenic CD5(+) B and CD5(-) B cells produce platelet glycoprotein-specific autoantibodies in chronic ITP

The objective of the present study is to determine splenic B-cell subsets and the ability of splenic CD5(+) B and CD5(-) B cells to produce platelet glycoprotein-specific autoantibodies in chronic idiopathic thrombocytopenic purpura (ITP). Splenic CD5(+) B cells were identified by two-color flow cytometric analysis in eight ITP patients. Magnetic activated cell sorting (MACS) purified splenic CD5(+) B cells and CD5(-) B cells were cultured separately in vitro. Glycoprotein-specific autoantibodies in culture supernatants and plasma were measured by modified monoclonal antibody immobilization of platelet antigen (MAIPA) assay. The percentage of splenic CD5(+) B cells in ITP patients was slightly higher than that in controls, with no statistical significance. Four ITP patients displayed plasma IgG autoantibodies against both GPIIb/IIIa and GPIb. Moreover, splenic CD5(+) B cells and CD5(-) B cells from these four ITP patients also produced high level of IgG anti-GPII(b)/III(a) and anti-GPI(b) antibodies. However, we were unable to detect IgM GP-specific autoantibodies in culture supernatant and plasma in these ITP patients. It is concluded that both splenic CD5(+) B cells and CD5(-) B cells produce platelet IgG GP-specific autoantibodies, and may all play a role in the pathogenic process of ITP.

CD5 expression in human B-cell populations

The origin of CD5+ B cells remains controversial. The differential response to ligation of CD5 resulting in apoptosis or proliferation provides insight into its roles in distinct human B cells. Here, Pierre Youinou, Christophe Jamin and Peter Lydyard review current knowledge of B-1 and B-2 cells, and propose that CD5 has different functions when expressed by different B-cell subpopulations.

Lymphoid Reconstitution After Autologous PBSC Transplantation With FACS-Sorted CD34+ Hematopoietic Progenitors

T-cell and B-cell reconstitution was studied in nine patients who received fluorescence activated cell sorter (FACS)-sorted autologous CD34+ hematopoietic progenitor cells (HPC). The mean numbers of T cells (CD3+), B cells (CD19+) and CD34+ HPC administered to each patient were .004, .002, and 1.8 × 106 cells/kg, respectively. After high-dose myeloablative chemotherapy (busulfan, cyclophosphamide, etoposide) CD34+ HPC were infused and lymphoid reconstitution was monitored using flow cytometry and reverse transcriptase-polymerase chain reaction (RT-PCR) amplification of VDJ T-cell receptor (TcR) sequences. Restoration of normal numbers of peripheral blood T cells and B cells among recipients of FACS-sorted CD34+ HPC was delayed compared to recipients of non-T-cell–depleted PBSC autografts. In both patient groups, the circulating T cells were primarily CD4−, CD8+, αβ TcR+, and CD45RO+, CD45RA− during the first 2 months after transplant. Subsequent increases in the frequency of CD45RA+ CD45RO− T cells occurred at 2 to 3 months after transplant, suggesting maturation of CD34+hematopoietic progenitors to “naive” T cells. Analysis of the TcR repertoire after hematopoietic reconstitution demonstrated decreased diversity of Vβ TcR expression associated with global decreases in the absolute number of total peripheral blood T cells and most Vβ TcR+ subsets. Three of nine recipients of FACS-sorted CD34+ HPC demonstrated significant increases in the percentage of γδ+ peripheral T cells and CD5+ B cells at 3 to 9 weeks after transplantation, and all patients had transient oligoclonal expansions of T cells expressing specific Vβ TcR. Transplantation with highly purified CD34+ HPC results in reduced diversity of the peripheral T-cell repertoire during the early post-transplant period compared with patients receiving unmanipulated or MoAb-depleted transplants.

Lymphoid Reconstitution After Autologous PBSC Transplantation With FACS-Sorted CD34+ Hematopoietic Progenitors

T-cell and B-cell reconstitution was studied in nine patients who received fluorescence activated cell sorter (FACS)-sorted autologous CD34+ hematopoietic progenitor cells (HPC). The mean numbers of T cells (CD3+), B cells (CD19+) and CD34+ HPC administered to each patient were .004, .002, and 1.8 × 106 cells/kg, respectively. After high-dose myeloablative chemotherapy (busulfan, cyclophosphamide, etoposide) CD34+ HPC were infused and lymphoid reconstitution was monitored using flow cytometry and reverse transcriptase-polymerase chain reaction (RT-PCR) amplification of VDJ T-cell receptor (TcR) sequences. Restoration of normal numbers of peripheral blood T cells and B cells among recipients of FACS-sorted CD34+ HPC was delayed compared to recipients of non-T-cell–depleted PBSC autografts. In both patient groups, the circulating T cells were primarily CD4−, CD8+, αβ TcR+, and CD45RO+, CD45RA− during the first 2 months after transplant. Subsequent increases in the frequency of CD45RA+ CD45RO− T cells occurred at 2 to 3 months after transplant, suggesting maturation of CD34+hematopoietic progenitors to “naive” T cells. Analysis of the TcR repertoire after hematopoietic reconstitution demonstrated decreased diversity of Vβ TcR expression associated with global decreases in the absolute number of total peripheral blood T cells and most Vβ TcR+ subsets. Three of nine recipients of FACS-sorted CD34+ HPC demonstrated significant increases in the percentage of γδ+ peripheral T cells and CD5+ B cells at 3 to 9 weeks after transplantation, and all patients had transient oligoclonal expansions of T cells expressing specific Vβ TcR. Transplantation with highly purified CD34+ HPC results in reduced diversity of the peripheral T-cell repertoire during the early post-transplant period compared with patients receiving unmanipulated or MoAb-depleted transplants.

CD5+ low-grade marginal zone B-cell lymphomas with localized presentation

Marginal zone B-cell lymphomas (MZBCLs) are low-grade lymphomas that characteristically lack CD5 expression. However, rare cases of MZBCL have been described in which the lymphomatous B cells coexpress CD5 (CD5+ MZBCL). In 7 of 9 reported CD5+ MZBCLs, there was evidence of widespread disease. We report four additional cases of CD5+ MZBCL. Three cases were low-grade B-cell lymphomas of mucosa-associated lymphoid tissue (MALT) involving the lungs, the conjunctiva (bilateral), and the uterus. The remaining case represented a monocytoid B-cell lymphoma involving a posterior cervical lymph node. Southern blot hybridization did not show rearrangements of bc11 or bc12 in the three cases analyzed. All four patients had localized disease and normal peripheral blood counts. Staging of bone marrow biopsies from three patients did not show evidence of bone marrow involvement. The remaining patient had bilateral conjunctival lesions that were present for 15 years without progression. These four additional cases of CD5+ MZBCL show that this group of low-grade B-cell lymphomas occasionally may exhibit an atypical phenotype. Furthermore, in this study, the CD5+ MZBCLs were clinically localized at presentation, in contrast to most other reported cases, which have had dissemination to bone marrow or peripheral blood.

Trisomy 12 and p53 deletion in chronic lymphocytic leukemia detected by fluorescence in situ hybridization: association with morphology and resistance to conventional chemotherapy

The incidence of trisomy 12 and p53 deletion was studied in a group of chronic B-lymphocytic leukemia (B-CLL) patients, using fluorescence in situ hybridization (FISH). Trisomy 12 was detected in eight of 50 patients (16%) and p53 deletion in six of 38 cases analyzed (15.8%). A statistically significant difference was observed between the incidence of trisomy 12 in patients with typical and atypical morphology (3.03% versus 41.18%). No correlation was found between this alteration and the rest of the clinical and biological parameters studied (adenopathies, hepatomegaly, splenomegaly, lymphocyte count, staging, CD11c expression, and resistance to chemotherapy). The p53 deletion was correlated with the presence of hepatomegaly and splenomegaly, advanced stage of disease, and resistance to conventional chemotherapy. The application of FISH to whole blood cell nuclei, without prior manipulation or culture, showed a higher percentage of cells with trisomy 12 than when the method was used following culture. We conclude that 1) FISH is a simple and sensitive technique for the detection of numerical and structural chromosome abnormalities; 2) Its application to uncultured samples obviates the alteration of results originated by the probable growth advantage of the normal or neoplastic cell population in vitro; 3) Trisomy 12 appears to define a B-CLL subgroup of atypical morphology; and 4) The p53 deletion is correlated with advanced stage of disease and resistance to treatment.

Structure and function of natural antibodies

Natural antibodies arise independently of known antigenic stimulation, are mostly IGM, polyreactive, and are generally encoded by V genes in germline configuration. Polyreactive IgM natural antibodies are produced by mainly B-1 cells which account for most of the B cell repertoire in the fetus and neonate, and possibly play a major role in the development and physiology of the human B cell repertoire. Although endowed with self-reactivity, natural antibodies also bind exogenous antigens [73, 74]. Exposure to environmental antigens is not necessary for the emergence of natural antibody-producing cell precursor clones to exogenous antigens, as suggested by the significant population of B cells capable of producing antibodies to a variety of bacterial antigens in germ-free animals. Because of their ability to bind a variety of exogenous antigens, including those on bacteria and viruses, natural antibodies play a major role in the primary line of defense against infections. A central issue related to the understanding of the physiopathologic roles of natural antibodies is whether precursors of cells producing natural antibodies, B-1a and B-1b lymphocytes, are capable of undergoing an antigen-driven clonal selection process, thereby producing autoantibodies with a high affinity for the selecting antigen. In this respect, we have clearly established that B-1 cells can express a hypermutation mechanism similar to that of conventional (B-2) cells. Furthermore, we have shown by gene shuffling, site-directed mutagenesis, and in vitro human Ig gene expression, that the main structural correlate for antibody polyreactivity is provided by the somatically generated H chain CDR3. We have also shown that this Ig V region provides the main structural correlate for antigen-binding in monoreactive antigen-induced autoantibodies. These findings in the human are at the basis of our proposed structure-function model in which the antigen binding features of the germline template antibody are dictated by the somatically generated H chain CDR3, and perhaps, but at a lower degree, L chain CDR3; the point-mutation changes underlying the antigen-driven affinity maturation process would impact mainly the Ig V gene encoded segments. This structure-function model is being tested in our laboratory by analyzing the antigen binding activity of somatically mutated polyreactive autoantibodies that have been structurally reverted to their original putative unmutated configuration. Precise identification of the Ig gene and/or somatic recombination products mediating recruitment of unmutated B cell clonotypes, as well as those that are preferentially modified by an antigen-dependent selection process, should further our understanding of the mechanisms that shape the B cell repertoire in development and disease.

Multiparametric immunophenotyping of B cells in peripheral blood of healthy adults by flow cytometry

The investigation of patients suffering from malignant lymphomas of the B-cell type requires flow cytometric immunophenotyping. Several reports described the expression of almost all B lineage antigens on normal and abnormal B lymphocytes. Thus, immunophenotyping of lymphomas must be interpreted in the context of the reference values obtained for healthy control individuals. For this purpose multiparametric flow cytometric analysis offers the unique feature for lymphocyte subset analysis. In the present study B lymphocytes in the peripheral blood of healthy adults were investigated by multiparametric flow cytometric immunophenotyping for the detection of the frequency (in percent) of antigens provided by the revised European-American classification of lymphoid neoplasms (REAL) classification. Thus, 84 healthy adults were investigated and grouped by age (average ages were as follows: group 1, 25.38 years; group 2, 33.86 years; group 3, 44.17 years; group 4, 55.67 years; group 5, 66.67 years). Analysis was done for surface immunoglobulins (kappa and lambda chains of immunoglobulin M [IgM] and IgD) as well as CD10, CD11c, CD23, CD38, CD103, FMC-7, and B-B4. Three-color immunophenotyping was performed for kappa/CD19/CD5, lambda/CD19/CD5, surface IgM/surface IgD/CD19, FMC-7/CD19/CD5, CD103/CD11c/CD19, CD10/CD23/CD19, and CD38/B-B4/CD19 by live gating of CD19+ events (n = 2,000). Although some numerical differences could be obtained for the different groups, statistical differences (P < 0.005) could only be obtained for the CD19+/CD5+ B-cell subset, which was decreased in the elderly patients (group 5). The established two-color and three-color stainings will serve as a basis for future multiparametric immunophenotyping of abnormal lymphocytes (e.g., for patients suffering from non-Hodgkin's lymphoma of the B-cell type).

Immunophenotyping of B lymphocytes by multiparametric flow cytometry in bone marrow aspirates of healthy adults

Establishing reference ranges by multiparametric immunophenotyping of mature B cells in bone marrow of healthy adults is of interest because the detection of bone marrow infiltration and persistence of light chain restriction, as well as discrimination between reactive and malignant lymphocytes are important applications of B-cell immunophenotyping. To determine the pattern of antigens as expressed by malignant mature B lymphocytes in the present study, bone marrow aspirates of healthy adults were investigated for the presence and percentage frequency of those antigens as defined for immunophenotyping of B cells by the REAL Classification. For this purpose, analysis of CD19-positive B lymphocytes by 'live gate' analysis was performed. The established two-color as well as three-color stainings will serve as a basis for future investigations designed to test multiparametric analysis of B lymphocytes in bone marrow aspirates. All investigated antibodies stained with varying percentage frequency on B-cell subtypes, and no statistical significant difference was found between bone marrow aspirates of women and those of men. On the basis of this analysis, all the reported lineage antigen combinations are present both in malignant B lymphocytes and in normal B cells in considerable percentage frequency. These findings are of importance for follow-up investigations of patients with non-Hodgkin's lymphomas by multiparametric immunophenotyping.

Clinicopathological and immunophenotypic studies on 12 cases with B cell chronic lymphocytic leukemia

To clarify the histogenesis of B cell chronic lymphocytic leukemia (BCLL), clinicopathological and immunophenotypic studies were performed using a large panel of monoclonal antibodies on 12 cases with BCLL including three cases with prolymphocytic/chronic lymphocytic leukemia (CLL/PL). Immunophenotypically, CD19 and CD20 were positive for all cases of this series and CD5, CD21, CD22, CD23, CD25, CD38, Leu-8, KB-61, and bcl-2 protein were expressed in variable proportion from case to case. CD10, however, did not react. No alkaline phosphatase (ALP) positive cases were found. The phenotype of BCLL was similar to that of B cells of the mantle zone (MZ) of secondary follicle in the lymph node. It is therefore postulated that the neoplastic cells of BCLL in these cases might be derived from B cells of the MZ. Moreover, the cells possibly originated from the lymphocytes located in the inner layer of the MZ, since ALP+ B cells are usually observed in the outer layer of the MZ. The pseudofollicular (PF) pattern was observed in four biopsied lymph nodes among five cases tested, but no such a pattern in an aspiration clot of bone marrow. These four cases consisted of three cases with CLL and a case with CLL/PL. The immunohistochemical study showed that there were many proliferating cells showing Ki-67+ in the PF area of the lymph nodes. In these cases, leukemic cells might have developed from the PF area of the lymph node.

Trisomy 12 is uncommon in typical chronic lymphocytic leukaemias

The incidence of trisomy 12 was studied by conventional chromosome analysis in 111 patients referred as B-cell chronic lymphocytic leukaemia (B-CLL). Fluorescent in situ hybridization (FISH) was also applied in 34 of those patients with either a normal karyotype or no analysable mitoses. By karyotyping, trisomy 12 was present in 11.7% (13/111), whereas additional FISH increased the incidence to 14.4% (16/111). When subdividing our cases in either typical CLL (n = 90), fulfilling the FAB classification criteria, or atypical CLL (n = 21), with one or more variations from those criteria, the incidence of +12 by metaphase analysis was 3% and 48%, respectively. Additional FISH increased the incidence to 4% and 57%. The most common aberration in atypical CLL was FMC7 positivity (n = 11), followed by CD5 negativity (n = 8), strong surface immunoglobulin staining (n = 7) and atypical morphology (n = 6). Trisomy 12 could only be demonstrated in a small proportion of neoplastic cells in all positive cases. By FISH and/or karyotyping, all available samples at diagnosis of the disease were positive.

Immunohistologic detection of the primary follicle (PF) in human fetal and newborn lymph node anlages

The primary follicle (PF) emerges as a globular nest of follicular dendritic cells (FDC) and lymphocytes in the lymph node anlage in the 16th gestational week. It increases in size with age but no germinal center is found until several months later, after birth. Using a panel of monoclonal antibodies, the authors have defined phenotypes of component cells of the PF. The PF contains a B-cell population including IgM+, CD20+, CD21+, and CD24+ cells, together with a T-cell population including CD3+, CD4+, CD5+, and CD8+ but no IgG+ cells. It also contains many CD5+ B cells and several IgD+ and alkaline phosphatase-positive cells but few CD15+, CD25+, CD30+, CD38+, and Ki-67+ cells. CD24+ and dendritic reticulum (DRC)-1+ cells show an irregular meshwork pattern in the PF. CD5+ B cells appear even before the formation of the PF and increase after formation of the PF. The lymphocytic phenotype of the PF is similar to that of the mantle zone of the secondary follicle. The phenotypic characteristics indicate that the PF appears as an aggregation of CD5+ B cells and plays an important role as the ancestor of the secondary follicle as well as helper T cells and FDC.

Human CD5-positive B cells in lymphoid malignancy and connective tissue diseases

The current literature on human CD5-positive B cells (CD5 + B cells) has been analysed, with a special emphasis on non organ-specific auto-immune diseases. Malignant cells of most of the chronic lymphoid leukaemias of the B cell lineage express the CD5 molecule. Antibodies of the IgM class produced by leukaemic B cells are multispecific auto-antibodies. The CD5 + B cell subset may be expanded in non organ-specific autoimmune diseases, such as rheumatoid arthritis, primary Sjögren's syndrome, systemic lupus erythematosus. This holds true for various conditions, including organ-specific auto-immune diseases. Since auto-immune features are common in lymphoproliferative disorders, and the latter be a complication in non organ-specific auto-immune diseases, CD5 + B cells may represent an intermediary between these auto-immune diseases and B cell lymphoproliferations. Studies on the regulation of CD5 + B cell production and function are likely to shed light on the aetiology of, and pathogenetic mechanisms operating in the different disease states.

Mantle cell lymphoma: an update

Mantle cell lymphoma is a distinctive pathologic entity that incorporates the previous histopathologic categories of centrocytic lymphoma and lymphocytic lymphoma of intermediate differentiation. These lymphomas are characterized by common histologic and immunologic characteristics that suggest derivation from the follicular mantle zone. Mantle cell lymphomas are characterized by the t(11;14) (q13;q32) translocation and its molecular counterpart bcl-1 rearrangement. This translocation activates a gene called BCL-1/PRAD-1. The identification of the BCL-1 gene product as a cyclin has added a new dimension to our understanding of the variety of mechanisms involved in lymphomagenesis.

Phorbol ester-induced hairy cell features on chronic lymphocytic leukemia cells in vitro

Leukemic cells from eight patients with chronic lymphocytic leukemia were isolated and cultured in the continuous presence of 12-O-tetradecanoylphorbol 13-acetate (TPA) at a concentration of 1.6 x 10(-9) M for 4-10 days. Aliquots of cells were then analyzed at intervals of 24-72 hr for changes in morphology, acid phosphatase staining (AP), and expression of two hairy cell-associated surface antigens, HCL1 (CD22, Leu 14) and HCL3 (CD11c, Leu M5). All cases studied showed typical B-CLL phenotype, and only a small proportion of cells expressed CD22 and CD11c (mean 7% and 4.9%, respectively). TPA treatment induced the coexpression of CD22 (mean 49%) and CD11c (mean 48%) and tartrate-resistant acid phosphatase in seven of eight cases. Morphologically, cells in TPA cultures expressed hairy cell features that were evident in light and electron microscopic studies. Collectively these changes indicate that TPA can induce hairy cell features on CLL cells in vitro, suggesting the later maturational stage of HCL compared with CLL.

Immunoglobulin V gene expression in CD5 B-cell malignancies

Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphomas (SLL) generally are malignancies of CD5 B cells. Immunophenotypic and clinicopathologic data, however, are required to distinguish subtypes that apparently have a different cytogenesis than that of conventional CLL or SLL. In addition to expressing CD5, neoplastic cells of the latter are also distinctive in that they frequently coexpress surface immunoglobulin (Ig), bearing one or more cross-reactive idiotypes (CRIs) (e.g. 17.109, G6,) that commonly are found on monoclonal IgM autoantibodies. The frequent occurrence of such CRIs reflects both the biased rearrangement and subsequent selected expression of Ig V genes with little or no somatic mutation. IgM/L CLL, for example, frequently (8/33) harbor abortive Ig rearrangements involving Humkv325, the VK gene encoding the 17.109-CRI. Also, the VH1 gene(s) encoding the G6 CRI accounts for over 10% of all VH genes and over 60% of all the VH1 genes used in randomly selected common CLL/SLL. Furthermore, comparison with the Ig expressed by nonmalignant G6 CRI+ B cells reveals an apparent restriction in the CDR3 of IgH expressed by G6 CRI+ CLL. Coupled with the observed potential bias in antibody light chain and heavy chain pairing in B-CLL, these data suggest that the autoantibodies expressed in this disease are selected based on antigen-binding activity. Collectively, our studies indicate that nonstochastic Ig V gene rearrangement and subsequent selection may influence the Ig repertoire expressed in this common B-cell malignancy.

B cells expressing CD5 antigen are markedly increased in peripheral blood and spleen lymphocytes from patients with immune thrombocytopenic purpura

By two-colour flow cytometric analysis, we examined the proportion of B lymphocytes bearing CD5 cell surface antigen (CD 5+ B cells), which are capable of producing autoantibodies, both in peripheral blood and spleen from patients with chronic immune thrombocytopenic purpura (ITP). The percentage of CD5+ B cells in peripheral blood lymphocytes (PBLs) was significantly increased (P less than 0.005) in patients with ITP (3.7 +/- 2.2%, n = 30) as compared with normal controls (1.7 +/- 0.7%, n = 28). However, there was no correlation between the percentages of circulating CD5+ B cells and platelet counts. The percentage of splenic CD5+ B cells in ITP patients was much more increased (9.0 +/- 4.5%, n = 9), P less than 0.005) compared with that of other disorders (3.2 +/- 0.5%, n = 5). Furthermore, isolated splenic CD5+ B cells from two out of five ITP patients produced high levels of IgM-type, platelet-bindable antibodies (PBIgM) after stimulation with Staphylococcus aureus Cowan I (SAC), while CD5- B cells isolated from the same spleen or splenic CD5+ B cells from other non-autoimmune disorders failed to produce significant amount of PBIgM. In three ITP patients, no increase in PBIgM was detected despite SAC stimulation. The increased proportion of CD5+ B cells in peripheral blood and spleen, and their ability to produce anti-platelet antibodies indicate that they are directly involved in the autoimmune pathogenesis in ITP.

Relationship of the CD5 B cell to human tonsillar lymphocytes that express autoantibody-associated cross-reactive idiotypes

We examined human tonsillar B cells for expression of autoantibody heavy-chain or kappa light-chain cross-reactive idiotypes (CRIs), respectively defined by murine MAbs G6 or 17.109. We find 17.109 or G6 each specifically binds a subpopulation of B cells, respectively reacting with 3.8 +/- 3% (mean +/- SD) or 2.0 +/- 1.2% of all tonsillar lymphocytes. Cells reactive with both 17.109 and G6 comprise only 0.4 +/- 0.3% of tonsillar lymphocytes. Although each tested specimen had 17.109-positive cells, 2 of 19 tonsils (11%) did not have any G6-reactive cells. We find that CRI-positive cells and CD5 B cells both co-express slgD but fail to bind peanut agglutinin or MAbs specific for CD10, indicating that both cell types reside in the mantle zones of secondary B cell follicles. However, less than half of the B cells bearing one or both of these CRIs express detectable levels of CD5. Nevertheless, we find that G6-reactive lymphocytes constitute a multiclonal population of cells that express homologous heavy chain variable region genes, each rearranged to one of several distinct and apparently nonmutated D and JH gene segments. Collectively, these studies indicate that expression of nondiversified autoantibody-encoding variable region genes may not be an exclusive property of B cells that bear detectable levels of the CD5 surface antigen.

Increased CD5-positive B lymphocytes in type I diabetes

CD5+ B lymphocytes have been implicated in the production of polyspecific and monospecific antibodies that bind self-antigens, and increased proportions of this B cell subset occur in patients with some autoimmune diseases. We investigated the proportion of peripheral blood CD5+ B lymphocytes in type I diabetic patients. Compared with 18 age-matched healthy subjects, 11 out of 28 (39.2%) type I diabetic patients had increased proportions of circulating CD5. B lymphocytes with no alterations in the numbers of circulating B and T lymphocytes. Although all patients with increased CD5 B lymphocytes also had serum islet cell antibodies and/or insulin autoantibodies, the occurrence of increased proportions of CD5+ B lymphocytes and serum autoantibodies was not significantly correlated. Increased proportions of CD5+ B lymphocytes was not related to the time elapsed since the clinical onset of diabetes. In addition, regardless of being increased or normal, the proportion of CD5+ B lymphocytes appeared as a relatively constant phenotype after 1 year of follow-up studies at 3-month intervals in eight patients. Although the significance of these findings remains to be established, the possibility exists that CD5+ cells play a role in the pathogenesis of type I diabetes.

Histomorphologic and immunophenotypic spectrum of primary gastro-intestinal B-cell lymphomas

In order to compare primary gastro-intestinal (GI) B-cell lymphomas histomorphologically and immunophenotypically with orthologous steps of B-cell differentiation within the mucosa-associated lymphoid tissue (MALT) of the GI tract, a comprehensive panel of well characterized leucocyte differentiation antigens was composed. It comprised immunoglobulin constituents CD5, CD10, CD11c, CD20, CD23, CD24, CD30, CDw32, CD38, CD39, CDw75, CD76, and vimentin. These antigens yield characteristic immunoprofiles for the following B-cell compartments of the MALT, per se closely linked to cytologically distinct B-cell phenotypes: mantle zone (MZ), extrafollicular compartment (EF), follicle center (FC), and plasma-cell compartment (PC). An unselected series of 31 MALT B lymphomas (13 of low and 18 of high grade malignancy) was classified histologically in routine preparations and subsequently characterized immunohistochemically using fresh frozen tissue, monoclonal antibodies (MAbs) against the antigen panel listed above, and an indirect immunoperoxidase method. The final classification considered both morphology and immunoprofile of tumor cells. Ten tumors were "typical" in both respects: 2 closely corresponded to MZ, 5 to EF, 2 to FC and 1 to PC. The remaining 21 cases were characterized as "atypical" because of anaplastic cytology and/or abnormal co-expression and/or loss of antigens. A hybrid EF/FC phenotype was most frequently observed together with centrocyte-like or centrocytic anaplastic cytology of tumor cells. We conclude that MALT B-cell neoplasia comprises a broad spectrum of histo- and immunophenotypes ranging from well differentiated forms closely mimicking normal B-cell development to highly abnormal tumors which cannot be subclassified.

B cells of chronic lymphatic leukemia express V genes in unmutated form

In order to investigate whether the leukemic B cells in B-CLL express immunoglobulin genes in mutated or unmutated form, independent cDNA clones of one patient with B-CLL expressing heavy and light chain V region genes were sequenced. The sequences of both the VH and V kappa clones were identical. The V genes could be assigned to known germline V genes. No somatic mutations were found. At the V kappa-J kappa border there is an insertion of N-sequences which are only rarely found in immunoglobulin light chain genes. Our study confirms other published data on V gene expression in B-CLL in that the surface immunoglobulins in these tumors are unmutated.

Mantle zone lymphoma. A clinicopathologic study of 22 cases

A clinicopathologic analysis of 22 cases of mantle zone lymphoma (MZL) was performed. In lymph node sections, MZL was characterized by the proliferation of neoplastic small lymphoid cells in wide mantles around benign germinal centers. Eighteen cases were of the intermediate lymphocytic type and four cases were of the small lymphocytic type. Immunohistologic analysis of paraffin sections revealed the following characteristic immunophenotype of MZL: L26, LN2, NUB1 and T2/48 positive, and LN5, LN1, AF6 and UCHL1 negative. The immunophenotype of MZL was identical to that of normal primary lymphoid follicles and the mantle zones of secondary follicles, except for the absence of staining with LN5 in MZL. The median age of the patients was 63 years, and the male-to-female ratio was 1.2:1. B symptoms were present in 55% of the patients, and 81% had splenomegaly. An absolute lymphocytosis was present at the time of initial diagnosis in 13% of the patients, and 67% had bone marrow involvement by lymphoma. Thirteen percent of the patients had Stage II disease, 23% had Stage III disease, and 64% had Stage IV disease. All 22 patients received some form of therapy, with 73% receiving multiagent chemotherapy. Eleven patients achieved a complete remission at some time during their course. The overall median survival of the entire group was 88 months. Clinical features which appeared to influence survival adversely included an absolute lymphocyte count above 4000/microliters, a platelet count less than 100,000/microliters, and male sex. Achievement of a complete remission at any time favorably influenced survival. Pathologic features which appeared to influence survival adversely were a mitotic rate of 10 or more per 10 high-power fields (HPF) and the presence of 40 or more large lymphoid cells per 10 HPF. These findings lead the authors to conclude that MZL is a distinctive form of low-grade non-Hodgkin's lymphoma.

Analysis of surface antigen expression of human immunoglobulin-secreting cells: phenotypic heterogeneity in normal counterparts of myeloma cells

Human myeloma cells are malignant counterparts of plasma cells which represent the most differentiated B cells. Myeloma cells are, however, heterogeneous in their surface antigen expression (Katagiri et al, 1984, 1985), which may reflect that normal plasma cells have a spectrum of differentiation. To test this hypothesis, immunoglobulin-secreting cells (ISC) of non-neoplastic nature were studied with regard to their surface antigen expression by using a combination of reverse haemolytic plaque assay and complement-dependent cytolysis. Non-neoplastic ISC were found to have a broad spectrum of differentiation stages from the immature type of CD20+, HLA-DR+, CD38+ in the peripheral blood to the mature type of CD20-, HLA-DR-, CD38+ in the bone marrow. In patients with polyclonal B cell activation (PBA), ISC showed a more immature antigen expression in comparison with ISC in normal controls or patients without PBA. The surface antigen development of ISC was clearly demonstrated throughout the stages in the analysis of mitogen-induced ISC in vitro. No significant difference in the surface phenotype of ISC was found among heavy chain classes. Thus, non-neoplastic ISC show a spectrum of differentiation similar to that of myeloma cells, depending on the site where ISC are located, and on the degree of PBA in vivo.

Characterization of B cells in severe combined immunodeficiency disease

The circulating lymphoid cells of eight consecutive untreated infants with severe combined immunodeficiency disease (SCID) with B cells were analyzed for surface marker expression and function. The B cells of these children expressed sIg, HLA-DR, CD19 (B4), CD20 (B1), CD21 (B2), Leu-8, and lacked expression of CD10 (CALLA), as do normal peripheral blood B lymphocytes. SCID B cells also expressed antigens that are normally absent or present on only a minor subset of circulating adult B lymphocytes, including CD1c (M241), CD38 (OKT10), CD23 (PL13), with or without concomitant CD5 (Leu-1) expression. The B cells of these children were capable of proliferating in vitro when stimulated with Staphylococcus aureus Cowan I. However, in the presence of pokeweed mitogen, S. aureus Cowan I, and normal T cells, the sIg+ cells of these children produced only IgM. Studies performed on normal B cells obtained from cord blood, young children, and adults reveal that whereas cord blood B cells are predominantly CD1c, CD38, and CD23 positive, B-cell expression of these antigens decreases with age. Cord blood B cells, similar to SCID B cells, produce only IgM when stimulated in vitro with pokeweed mitogen and S. aureus Cowan I. Based on these observations, we hypothesize that SCID B cells represent a population of B cells present during normal B-cell ontogeny which becomes a minor subset when an individual develops full immunologic competence.

Production of autoantibodies by CD5-expressing B lymphocytes from patients with chronic lymphocytic leukemia

CD5-expressing B lymphocytes from patients with selected chronic lymphoproliferative disorders were used to determine whether monoclonal populations of CD5+ human B cells produce autoantibodies. CD5+ B cells from 19 patients with chronic lymphocytic leukemia (CLL) and one with diffuse well-differentiated lymphocytic lymphoma (DWDL) were cultured, with and without mitogenic stimulation, to obtain Ig from these cells. 17 of the 20 samples produced Ig in vitro. mAb from nine of the 17 patients were reactive with either IgG, ssDNA, or dsDNA. In every instance, the autoantibodies displayed monotypic L chain usage that correlated precisely with the L chain expressed on the CD5+ leukemic B cell surface. These monoclonal autoantibodies varied in their degree of antigenic specificity; some were quite specific, reacting with only one antigen, whereas others were polyspecific, reacting with two or all three autoantigens tested. Three features distinguish these autoantibodies from those observed in prior studies of CD5+ B cells. First, they are clearly the products of monoclonal populations of CD5+ cells; second, several react with dsDNA, a specificity not previously reported and often seen in association with significant autoimmune disorders; and third, two of the monoclonal autoantibodies secreted by the CD5+ clones were of the IgG class. Although not all of the Ig-producing, CD5-expressing clones elaborated mAbs reactive with the autoantigens tested, greater than 50% did. It is possible that with a broader autoantigenic panel or with larger quantities of CLL/DWDL-derived Ig, even more autoantibody-producing clones might be identified. These studies may have important implications for the antigenic specificity of subsets of human B lymphocytes as well as for lymphoproliferative and autoimmune disorders in general.

Monoclonal antibody directed to human T-cell malignancy antigen

A murine monoclonal antibody (B2D) against a cultured pre-T acute lymphoblastic leukemia (ALL) cell line THP-6 has been produced. The antibody reacted with seven out of eight cultured T-ALL cell lines and with leukemic cells from three out of four T-ALL/lymphoma patients. The antibody did not react with normal T and B lymphocytes, monocytes, granulocytes, platelets, erythrocytes, bone marrow lymphoid-like precursor cells, thymocytes and other acute and chronic leukemic cells of non-T cell origin. Furthermore, B2D did not react with phytohemagglutinin-activated T cells nor with concanavalin A-activated T cells. The molecules immunoprecipitated with B2D had molecular weights of 50-55 kD. Thus, B2D seems to be highly specific for T-cell malignancies. These results show that B2D defines one of human leukemia antigens which are expressed on the cell surface of T-ALL cells. Monoclonal antibody B2D may be useful for the subclassification of T-ALL cells and has therapeutic potential for a certain type of T-ALL.

Histological and immunohistological analysis of human lymphomas

Morphological and immunological characteristics of lymphoproliferative diseases are reviewed. In particular, a basic distinction is made between non-Hodgkin's lymphomas and Hodgkin's disease. As to the non-Hodgkin's lymphomas, emphasis is given to the problems of classification, technical approach, histogenesis, and prognosis. The authors adopt a version of the Kiel Classification modified to take account of new knowledge regarding T-cell lymphomas. The value of immunophenotyping in making an accurate distinction between the various categories is stressed; immunocytochemical detection of the growth fraction is also discussed and then proposed as a new prognostic tool. Finally, the criteria for differential diagnosis between non-Hodgkin's lymphomas, malignant histiocytosis, non-lymphoid large cell tumors, and atypical immune reactions are outlined.

Phenotypic heterogeneity of B- and T-cell differentiation antigens in B-CLL

Peripheral blood from 38 B-CLL patients was studied by flow cytometry with 25 clustered or non-clustered monoclonal antibodies (moAbs) in order to characterize the cell surface phenotype of lymphoid cells. All moAbs chosen detected B or CD1-8 T-cell differentiation antigens or MHC class II antigens. The results showed a heterogeneity in the leukemic cell reactivity with the various moAbs and between patients. The restricted B-cell antigens recognized by BL14, Y2955 and anti-class II moAbs were constantly expressed in leukemic cells, while B-cell antigens reacting with FMC7 and BL13 moAbs were variably detected. In addition to CD5 antigens, other T-cell markers, including several epitopes of the CD1 group, were also found to be present on the leukemic cell surface in several cases. The relationship between the various clinical and/or biological features of the disease and the cell surface phenotype was studied. Our results indicated a correlation between the lymphoid cell reactivity with M241 (CD1) and BL13 (CD21) and the severity of the disease.

Ovalbumin-specific human B-cell activation and maturation. The absence of final maturation is due to the incapacity of ovalbumin-activated T cells to produce maturation factors

By means of a panel of monoclonal antibodies it is demonstrated that, in cultures of human peripheral blood mononuclear cells (PBMC) with the T-cell-dependent (TD) antigen ovalbumin (OA), responding B cells are activated from the resting state. The differentiation of the activated B cells to high rate-secreting plasma blasts, however, is arrested in an early activation phase, in which they can be detected as low rate-secreting plaque-forming cells. The arrest does not occur when stimulation with OA occurs in the presence of antigen-nonspecific activation and maturation factors, which are provided in the culture by the anamnestic response to the TD antigen tetanus toxoid.

Circulating cerebriform lymphoid cells (Sezary-type cells) in a B-cell malignant lymphoma

Circulating cerebriform lymphoid cells (Sezary cells) are considered to be highly predictive of cutaneous T-cell Lymphoma (CTCL). A leukemic peripheral blood (leukocyte count 24.5 x 10(9)/l) composed predominantly of cerebriform cells was found in a 75-year-old man presenting with weight loss and generalized lymphadenopathy but without skin lesions. Cell suspensions studies and immunohistochemistry of peripheral blood revealed that the cerebriform cells were B-cells (IgM+ Kappa+, HLA DR+, Leu 1+, CALLA-, B1+, and OKT 10+). A variety of T-cell markers (other than Leu1) was negative. Computer-assisted morphometry confirmed a nuclear profile typical of CTCL (mean nuclear contour index, 7.47). A lymph node that underwent subsequent biopsy revealed a follicular malignant lymphoma of small to intermediate cells with similar morphologic and immunologic characteristics to the circulating cerebriform cells. The findings of a leukemic presentation of a cerebriform B-cell lymphoma extends the recent observation of nodal B-cell lymphomas composed of cerebriform cells and indicates that circulating cerebriform cells should not be considered to be exclusively of T-cell origin.

Cytoskeleton organization of normal and neoplastic lymphocytes and lymphoid cell lines of T and B origin

An anomalous organization of the cytoskeleton has been described in lymphocytes from chronic lymphatic leukaemia and in only few cell lines. We have now studied normal and neoplastic lymphocytes and lymphoid cell lines of both T and B lineage in order to detect morphological differences in the expression of microfilaments and intermediate filaments. Microfilaments appear to be well expressed by all the B cells, whereas a rich network of intermediate filaments is present in T cells and plasma cells. Most prominent changes occur in the latter system, which is almost lacking in cells of B chronic lymphatic and hairy cell leukaemia. Although the significance of the present findings is not yet clear, one might speculate that such alterations account for some of the aberrant functions and peculiar biologic properties of neoplastic lymphocytes.

Activation and differentiation antigen expression in B-cell non-Hodgkin's lymphoma

In an attempt to establish whether extended immuno-phenotyping allows more accurate definition of subgroups of B-cell non-Hodgkin's lymphoma (NHL) we have stained a series of 145 cases with a large panel of monoclonal antibodies that recognize B-cell differentiation and activation antigens. No antigen was expressed by all cases. The B-cell histogenesis in many cases could be confirmed only by using a panel of immunoglobulin and pan B-cell markers. There was marked phenotypic heterogeneity within and between major groups of B-cell NHL as delineated by the Kiel classification although the differentiation antigens CD5 (lymphocytic and centrocytic NHL) and OKT10 (plasma cell tumours) were more often expressed by certain morphological groups. The activation antigens 4F2 and transferrin receptor were expressed more strongly and more often by high grade NHL but other activation antigens (CD23 and CD25) were not more frequently associated with these tumours. Extended phenotyping may be of value in improving the understanding of biological abnormalities and processes involved in B-cell NHL, but we conclude that a limited panel of markers (CD3, CD5, CD22, CD45, IgM, kappa, and lambda) should be sufficient for routine diagnosis and classification of most cases.

Dendritic reticulum cell pattern as a microenvironmental indicator for a distinct origin of lymphoma of follicular mantle cells

Follicular dendritic reticulum cells (DRCs) are known to be normally present in primary follicles and both follicular centres and mantle zones of secondary follicles of peripheral lymphoid tissue. Involved frozen biopsy tissue specimens from eight cases of intermediate lymphocytic lymphoma/mantle zone lymphoma (ILL/MZL); eight cases of follicular centre cell lymphomas (FCCL) of the centroblastic/centrocytic type; and seven cases of well-differentiated lymphocytic lymphoma (WDLL) consistent with chronic lymphocytic leukaemia (CLL) were analysed immunohistologically with R4/23 (DRC-1) monoclonal antibody reactive with 'bystander' DRCs. As opposed to FCCL and most WDLL/CLL cases, the DRCs consistently formed a loose, ill-defined meshwork with a radiating or blurred outline in all MZL cases and one ILL. On the basis of the observed findings as well as from those reported in literature, the hypothesis is proposed that ILL/MZL originates from the follicular mantle zone and represents a distinct lymphoma entity owing to its peculiar immunostaining pattern of DRCs that allows it to be separated from both FCCL and WDLL/CLL. Moreover, the absence of DRCs in the microenvironment of other B-cell malignancies such as prolymphocytic leukaemia and hairy cell leukaemia, analogously with most CLL cases, would speak in favour of their different--possibly extrafollicular--compartment of origin within lymphoid tissue.

Analysis of T-cell-derived factors with the use of B-prolymphocytic leukemia cells

Mononuclear cells of five patients with B-prolymphocytic leukemia were tested for their functional capacities in vitro after stimulation. Leukemic B cells from these patients have a mature phenotypic marker profile and can be obtained in high numbers from peripheral blood. B cells of all five patients proliferated in response to phorbol myristate acetate. In one patient, this proliferation was strongly enhanced by the addition of T-cell-conditioned medium. Conditioned medium by itself or interleukin 2 in the presence or absence of the phorbol ester was not active. This enabled us to develop an assay for a B-cell growth factor different from interleukin 2. Next to their proliferative capacities, we found that malignant B cells of three of the five patients secreted large amounts of IgM when stimulated with pokeweed mitogen or interleukin 2 in the presence of allogeneic T cells. In the absence of these allogeneic cells, neither pokeweed mitogen nor interleukin 2 had any effect. However, T-cell-conditioned medium as well as the supernatants of two T-cell hybridomas induced strong IgM production in the absence of T cells. Thus, neoplastic B cells of some patients with B-prolymphocytic leukemia can be stimulated to proliferation and differentiation in vitro and can be used as an assay and model system to study the effect of T cells and/or T-cell factors in human B-cell activation.

A histogenesis of malignant lymphoma, small cleaved cell of the B cell type and intermediate lymphocytic lymphoma (mantle zone lymphoma). An immuno- and enzymehistochemical study

We have studied the histogenesis of malignant lymphoma (ML), small cleaved cell of the B-cell type and intermediate lymphocytic lymphoma (mantle zone lymphoma) by comparing immunophenotypes and ALP-activity of neoplastic cells with those of germinal center cells (follicular center cells) and mantle zone (MZ) cells of secondary follicles in non-neoplastic lymphoid tissues. The neoplastic cells in 3 cases of ML, follicular, small cleaved cell and 1 case of ML, small cleaved cell expressed the phenotypes similar to those of germinal center (GC) B lymphocytes (SIgM+, B1+, B2+, CALLA+, SigD-, IL-2R-, Leu-1- and ALP-). The neoplastic cells in 2 cases of ML, follicular, small cleaved cell and 12 cases of ML, diffuse, small cleaved cell displayed the characteristic phenotypes of MZ B lymphocytes (SIgM+, SIgD+, BA-1+, IL-2R+, Leu-1+ and ALP+). The phenotypes of 2 cases of mantle zone lymphoma were closely comparable with those of MZ B lymphocytes. These findings indicate that the histogenesis of ML, small cleaved cell of the B-cell type is heterogeneous and can be divided phenotypically into 2 types (GC B lymphocyte origin and MZ B lymphocyte origin). It is also apparent that intermediate lymphocytic lymphoma (mantle zone lymphoma) is derived from MZ B lymphocytes of secondary follicles.

Lymphoplasmacytoid lymphoma: an immunohistological study

Eighteen cases of lymphoplasmacytoid lymphoma (LPL) have been immunophenotypically characterized with a panel of 26 monoclonal antibodies. All cases expressed leucocyte common antigen, class II MHC and stained with B cell markers (CD19, CD20, CD22) although a variable proportion of tumour cells were noticed to have lost some B cell marker expression. There was some phenotypic heterogeneity with variable immunostaining with KB61, CD21, and CD5. A variable proportion of cells in all cases contained cytoplasmic immunoglobulin. Surface immunoglobulin light chain restriction was demonstrated in 11 cases and heavy chain predominance in 16 cases. Few tumour cells were proliferating as indicated by Ki67 immunostaining. A wide variation in number of macrophages and T lymphocytes were present in association with the tumours. A significant association between the expression of CD5 and the presence of peripheral blood lymphocytosis was noticed (p less than 0.003) but there was no association between CD5 and co-expression of IgM and IgD. This data supports an origin from non-germinal centre cells for LPL and suggests that CD5 expression by B cells may be related to lymphocyte migration. LPL shows some immunological heterogeneity and can present diagnostic difficulties, but its poor prognosis makes it an important category of lymphoma to recognise.

The simultaneous presentation of peripheral T-cell lymphoma and hairy cell leukemia

A patient who presented simultaneously with B hairy cell leukemia (HCL) and peripheral T-cell lymphoma (PTL) is described. The diagnoses of the two neoplasms were made by standard morphologic and cytochemical study and confirmed immunologically. There was no evidence of overlap in markers to suggest that they arose from a single clone of malignant cells. It is suggested that the simultaneous occurrence of the two neoplasms in the same patient reflects an underlying predisposition to the development of neoplasia in HCL.