BAFF-R, the major B cell-activating factor receptor, is expressed on most mature B cells and B-cell lymphoproliferative disorders

B cell-activating factor receptor (BAFF-R) is one of three known receptors for BAFF, a critical regulator of B- and T-cell function. In mice, BAFF-R is required for B-cell maturation and survival, and in mice and humans, the overproduction of BAFF is associated with autoimmune disease. We sought to determine the normal pattern of BAFF-R expression at specific stages of B- and T-cell development and whether this pattern of expression corresponds with related B- and T-cell neoplasms. Most circulating human B cells and a small subset of T cells are BAFF-R-positive. In reactive lymphoid tissues, BAFF-R is expressed by B cells colonizing the mantle zones, by a subset of cells within germinal centers, and rare cells in the interfollicular T-cell zone. BAFF-R is also expressed by B cells colonizing the splenic marginal zone. Seventy-seven (78%) of 116 cases of B-cell lymphoproliferative disorders were BAFF-R-positive by immunohistochemical and/or flow cytometric immunophenotypic analysis, including most cases of mantle cell lymphoma, follicular lymphoma, marginal zone lymphoma, chronic lymphocytic leukemia, hairy cell leukemia, and diffuse large B-cell lymphoma. In contrast, cases of precursor B lymphoblastic lymphoma, Burkitt lymphoma, and nodular lymphocyte-predominant Hodgkin lymphoma exhibit weak to negative staining for BAFF-R. All cases of classical Hodgkin lymphoma and T-cell lymphomas were BAFF-R-negative, including all cases of anaplastic large cell lymphoma, adult T-cell leukemia/lymphoma, angioimmunoblastic T-cell lymphoma, and peripheral T-cell lymphoma, unspecified. These findings highlight BAFF-R as a marker of both normal and neoplastic B cells and raise the possibility that BAFF-R expression is necessary for the survival of a subset of neoplastic B lymphocytes analogous to its known role in promoting normal B-cell maturation and survival.     

The CD45 isoform B220 identifies select subsets of human B cells and B-cell lymphoproliferative disorders

The B220 isoform of CD45, a pan B-cell marker in mice, is expressed by only a subset of human B cells that do not express the memory B-cell marker CD27, suggesting that it is a differentiation-specific isoform of CD45. We examined normal human peripheral blood B cells, secondary lymphoid tissue, and a range of human B-cell lymphoproliferative disorders for the expression of B220 by flow cytometric immunophenotyping and immunohistochemical staining. We found that a subset of human B cells in peripheral blood is positive for B220 by flow cytometric immunophenotypic analysis. In reactive lymphoid tissues, B220 is expressed by B cells occupying the mantle zones and by a subpopulation of germinal center cells, but, in contrast, marginal zone B cells in the spleen do not express B220. Of 94 cases of B-cell lymphoproliferative disorders, 33 (35%) were positive for B220 by flow cytometric immunophenotypic analysis, including most cases of marginal zone lymphoma, follicular lymphoma, and lymphoplasmacytic lymphoma. In contrast, all cases of precursor B lymphoblastic leukemia/lymphoma, mantle cell lymphoma, and chronic lymphocytic leukemia/small lymphocytic lymphoma were negative for B220. Immunohistochemical staining for B220 correlated with flow cytometric analysis for all cases studied by both methods. Our data demonstrate that B220 is expressed in a select subset of normal, reactive B cells in a pattern that is consistent with a marker of naive B cells. However, this restricted expression pattern is not seen in B-cell lymphoproliferative disorders. Discordance between the B220 expression patterns of normal mantle and marginal zone B cells and their respective neoplastic counterparts may aid in the distinction between normal and neoplastic proliferations at these anatomical sites.     

ZAP-70 expression in B-cell hematologic malignancy is not limited to CLL/SLL

ZAP-70 is a tyrosine kinase expressed in normal T cells and NK cells. Expression of ZAP-70 has been associated with poor prognosis in B-cell chronic lymphocytic leukemia and might be a surrogate marker for immunoglobin heavy chain (IGH) mutational status in that disease. Little is known about ZAP-70 expression in other hematologic malignant neoplasms. We examined 446 specimens representing a range of hematopoietic malignant neoplasms for ZAP-70 expression by immunohistochemical analysis. As expected, most T cell-lineage disorders and a subset of small lymphocytic lymphomas were positive. IGH mutational status corresponded to ZAP-70 expression in a small subset of small lymphocytic lymphoma cases subjected to sequence analysis. Of note, however, ZAP-70 was expressed in a minority of other types of B-cell lymphomas, including precursor B-cell acute lymphoblastic leukemia, diffuse large B-cell lymphoma, mantle cell lymphoma, and very rare cases of classic Hodgkin lymphoma. Immunohistochemical analysis represents an alternative method for assessing ZAP-70 expression and reveals that other B-cell malignant neoplasms express ZAP-70.     

CD40 ligand is constitutively expressed in a subset of T cell lymphomas and on the microenvironmental reactive T cells of follicular lymphomas and Hodgkin's disease.

Although CD40 has been extensively studied in B- and T-cell non-Hodgkin's lymphomas (NHLs)/leukemias, and more recently in Hodgkin's disease (HD), little is known about the expression of its ligand (CD40L) in lymphoproliferative disorders other than T-cell NHLs/leukemias. A series of 121 lymphoma/leukemia samples, including 35 cases of HD, 34 T-cell and 39 B-cells NHLs, 2 cases of adult T-cell leukemia/lymphoma, and 11 cases of T-cell acute lymphoblastic leukemia, were evaluated for CD40L expression by immunostaining of frozen tissue sections and flow cytometry with the anti-CD40L monoclonal antibody M90. CD40L was constitutively expressed by neoplastic cells in 15 of 36 (42%) T-cell NHLs/adult T-cell leukemia/lymphomas, almost invariably those displaying the CD4+/CD8- phenotype, whereas no CD40L-expressing tumor cells could be found in B-cell NHL and HD. Among T-cell acute lymphoblastic leukemias, CD40L was detected only on 2 cases displaying a stem-cell-like phenotype. In follicular B-cell lymphomas a large number of CD40L-expressing CD3+/CD4+ T lymphocytes were found admixed with tumor cells within the neoplastic follicles and in their surrounding areas. In the nonfollicular B-cell lymphomas, CD40L-positive CD3+/CD4+ T lymphocytes were few or absent. In all HD subtypes other than the nodular lymphocytic predominance, CD40L-expressing CD3+/CD4+ T lymphocytes were numerous in the HD-involved areas and were mainly located in close proximity to the Reed-Sternberg cells. Our data indicate that in human lymphomas CD40L is preferentially expressed by a restricted subset of T-cell lymphomas, mostly with CD4 immunophenotype. Finally, we have provided morphological evidence that CD40L may play an important role in the cell contact-dependent interaction of tumor B-cells (CD40+) within the neoplastic follicles or Reed-Sternberg cells (CD40+) in HD-involved areas and the microenvironmental CD3+/CD4+/CD40L+ T lymphocytes.     

Expression of heat-shock protein-90 in non-Hodgkin's lymphomas.

Heat-shock protein-90 (HSP90) inhibitors are currently being used in phase I clinical trials for treating patients with a variety of neoplasms including lymphomas. Using immunohistochemical methods, we assessed for HSP90 expression in 412 cases of non-Hodgkin's lymphoma. In B-cell lymphomas, HSP90 was moderately to strongly expressed in all cases of Burkitt's lymphoma (5/5, 100%), and in subsets of follicular lymphoma (17/28, 61%), diffuse large B-cell lymphoma (27/46, 59%), nodal marginal zone B-cell lymphoma (6/16, 38%), plasma cell neoplasms (14/39, 36%), small lymphocytic lymphoma/chronic lymphocytic leukemia (3/9, 33%), mantle cell lymphoma (12/38, 32%) and lymphoplasmacytic lymphoma/Waldenstrom macroglobulinemia (3/10, 30%). HSP90 was weakly expressed in six of 14 (43%) cases of extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue. In T-cell lymphomas, HSP90 was moderately to strongly expressed in subsets of anaplastic large-cell lymphoma (14/24, 58%; 9/12 ALK+ and 5/12 ALK-), precursor-T-cell lymphoblastic leukemia/lymphoma (20/65, 31%), unspecified peripheral T-cell lymphoma (8/43, 23%) and angioimmunoblastic T-cell lymphoma (2/17, 12%). HSP90 was weakly expressed in seven of 58 (12%) cases of mycosis fungoides. We conclude that HSP90 is commonly expressed in a subset of many types of B- and T-cell lymphoma. These data suggest that many lymphoma types are suitable targets for modulation of HSP90 activity, and that HSP90 inhibitors are a potential investigational therapy for lymphoma patients.     

Clusterin expression in malignant lymphomas: a survey of 266 cases.

Clusterin expression has been reported to be characteristic of systemic anaplastic large cell lymphoma and usually negative in cutaneous anaplastic large cell lymphoma as well as other lymphoma types. We surveyed clusterin expression using immunohistochemical methods in 266 cases of non-Hodgkin's lymphoma and Hodgkin's disease to further assess the diagnostic utility of this marker. Clusterin immunostaining was observed in 40 of 49 (82%) systemic anaplastic large cell lymphomas and 12 of 29 (41%) cutaneous anaplastic large cell lymphomas. Clusterin also was expressed in 5 of 43 (12%) diffuse large B-cell lymphomas (4 of 5 CD30+), 1 of 14 (7%) peripheral T-cell lymphomas, 1 of 32 (3%) cases of nodular sclerosis Hodgkin's disease, and 1 case of mycosis fungoides in large cell transformation. Clusterin was negative in all other neoplasms assessed including follicular lymphoma of all grades (n = 24), mantle cell lymphoma (n = 13), marginal zone B-cell lymphoma (n = 12), precursor T-cell or B-cell lymphoblastic leukemia/lymphoma (n = 10), mixed cellularity Hodgkin's disease (n = 8), chronic lymphocytic leukemia/small lymphocytic lymphoma (n = 7), Burkitt lymphoma (n = 7), mycosis fungoides (n = 4), nodular lymphocyte predominant Hodgkin's disease (n = 3), lymphoplasmacytic lymphoma/Waldenstrom macroglobulinemia (n = 2), and plasmacytoma (n = 2). We conclude that clusterin is a marker of anaplastic large cell lymphoma and that addition of clusterin to antibody panels designed to distinguish systemic anaplastic large cell lymphoma from classical Hodgkin's disease is useful. However, clusterin is also positive in a substantial subset of cutaneous anaplastic large cell lymphomas, a smaller subset of diffuse large B-cell lymphomas, and rarely in cases of peripheral T-cell lymphoma and nodular sclerosis Hodgkin's disease.     

Distribution of lymphocytes with interleukin-2 receptors (TAC antigens) in reactive lymphoproliferative processes, Hodgkin''s disease, and non-Hodgkin''s lymphomas. An immunohistologic study of 300 cases.

The authors investigated the distribution of interleukin-2 receptors (TAC antigen) in the lymph nodes of 300 patients with lymphoproliferative disorders. They used fresh-frozen sections to evaluate a possible correlation between the immunophenotype of specific lymphoid disorders and the presence or absence of TAC expression and to determine whether the TAC positivity of lymphoid cells contributes to the characterization of lymphoproliferative processes. All of the cases had previously been studied with a large screening panel of monoclonal antibodies and polyclonal antisera. Among 85 patients with a variety of benign reactive processes, the lymph nodes from 47 contained TAC-bearing lymphocytes in various patterns of distribution. Of 41 patients with Hodgkin's disease, 37 had TAC-bearing lymphocytes. Of 26 B-cell, well-differentiated lymphocytic lymphomas (WDL), 14 were diffusely TAC-positive and one had TAC-bearing cells in random distribution. Six cases of intermediate lymphocytic lymphoma were also studied, and three showed randomly distributed TAC-bearing lymphocytes. Of 19 patients with follicular or follicular and diffuse, poorly differentiated lymphocytic (PDL) lymphoma, 14 were TAC-positive. All 3 diffuse PDL lymphomas studied were TAC-negative. Among 23 cases of B-cell and 5 cases of T-cell mixed cell lymphoma, 15 and three, respectively, had TAC-positive lymphocytes. Of 39 large cell lymphomas (B-cell, 33; T-cell, 6), 14 were TAC-positive. All 13 cases of hairy cell leukemia were diffusely positive. Of 23 T-lymphoblastic lymphomas, only 1 showed positive TAC reactivity, which was focal. Of 5 cases of cutaneous T-cell lymphoma, 2 had TAC-bearing lymphocytes. Our study indicates that the TAC antigen is not lineage-specific, and that it may be expressed by lymphoid cells regardless of their phenotype.     

Monoclonal antibody HML-1, a marker for intraepithelial T cells and lymphomas derived thereof, also recognizes hairy cell leukemia and some B-cell lymphomas

Current views regard monoclonal antibody HML-1 as an exquisite marker for intraepithelial T cells and primary intestinal and cutaneous T-cell lymphomas. We show that HML-1 reacted with 11 of 12 cases of hairy cell leukemia, with 1 of 13 cases of primary gastrointestinal B-cell lymphoma, and with an unclassified large-cell B lymphoma of the thoracic wall. We conclude that HML-1 is not restricted to the T-cell lineage and that the HML-1 antigen is expressed in a small subset of both T- and B-cell neoplasms.     

The Leukocyte Semaphorin CD100 Is Expressed in Most T-Cell, but Few B-Cell, Non-Hodgkin’s Lymphomas

The 150-kd transmembrane protein CD100 is the first semaphorin protein shown to be expressed in lymphoid tissue. CD100 is present in the interfollicular T cell zones and is also expressed by B cells in the germinal centers of secondary lymphoid follicles, but not in the mantle zones. The CD100 molecule was recently cloned, and CD100 transfectants were shown to induce homotypic aggregation of human B cells and improve their viability in vitro, suggesting that CD100 may play a role in lymphocyte aggregation and germinal center formation. We studied the expression of CD100 in 138 clinical cases representing a range of lymphoproliferative disorders, to determine whether this molecule is expressed in these neoplastic processes. In general, we found CD100 expression to be common in peripheral T-cell non-Hodgkin’s lymphomas but rare in B-cell non-Hodgkin’s lymphomas. CD100 expression was not detectable in low-grade B-cell non-Hodgkin’s lymphomas, including cases of small lymphocytic lymphoma (18 cases), marginal zone lymphoma (10 cases), and mantle cell lymphoma (10 cases), as might be expected for these neoplasms that are not of follicular center cell origin. Surprisingly, we found that the vast majority of follicular lymphomas (37 of 40 cases) as well as diffuse large-cell lymphomas of B-cell type (35 cases) did not express CD100. The neoplastic cells in 3 of 11 cases of predominantly large-cell-type follicular lymphoma did express CD100. In contrast, all five cases of high-grade, small non-cleaved (Burkitt-like) B-cell lymphoma were immunoreactive for CD100 expression, as were 18 of 20 cases (90%) of malignant T cell neoplasms. Northern blot analysis of CD100 expression correlated with immunohistochemical findings. Absence of expression of CD100 by neoplastic follicular center B cells is a common feature in follicular lymphomas, but expression of CD100 by T cells is maintained in T-cell lymphoproliferative disorders.     

Expression of the diffuse B-cell lymphoma family molecule SWAP-70 in human B-cell neoplasms: immunohistochemical study of 86 cases.

SWAP-70 is a recently discovered member of the Dbl (diffuse B-cell lymphoma) family of signal transduction molecules that is abundantly expressed in B cells. SWAP-70 mediates lipid second-messenger signals to the cytoskeletal-organizing GTPase Rac, functioning as a guanine-nucleotide exchange factor. SWAP-70 is strongly expressed in germinal center B cells, with low-level expression in resting B-cells. Expression of SWAP-70 in neoplastic B cells has not been described. We report the immunohistochemical expression of SWAP-70 in 86 B-cell neoplasms. SWAP-70 was strongly expressed in 59 of the 86 cases: 2 of 10 (20%) precursor B-cell lymphoblastic leukemias, 2 of 2 (100%) precursor B-cell lymphoblastic lymphomas, 2 of 4 (50%) mantle cell lymphomas, 7 of 9 (78%) Burkitt lymphomas, 9 of 9 (100%) diffuse large B-cell lymphomas, 8 of 8 (100%) follicular lymphomas, 6 of 6 (100%) nodular lymphocyte predominant Hodgkin lymphomas, 0 of 8 (0%) classic Hodgkin lymphomas, 12 of 13 (92%) chronic lymphocytic leukemias, 3 of 3 (100%) nodal marginal zone lymphomas, 5 of 5 (100%) extranodal marginal zone lymphomas, 1 of 2 (50%) splenic marginal zone lymphomas, 2 of 3 (66%) hairy cell leukemias, and 0 of 4 (0%) plasma cell neoplasms. All 4 T-cell lymphomas were nonreactive for SWAP-70: 0 of 3 peripheral T-cell lymphomas and 0 of 1 anaplastic large cell lymphoma. These results suggest that a spectrum of neoplastic B cells maintains activation of this signal transduction pathway. This is the first report of the expression of a Dbl family molecule in human lymphoma and leukemia tissues.     

Distribution and ZAP-70 expression of WHO lymphoma categories in Shanxi, China: a review of 447 cases using a tissue microarray technique.

This study aims to assess the distribution of lymphoma subtypes in Shanxi, China, according to the World Health Organization (WHO) classification, and to compare the relative distribution with other areas of the world. H&E-stained tissue sections from the archives of the Shanxi Tumor Hospital, China, were reviewed and 447 cases with sufficient materials were selected for detailed study. A panel of antibodies and probes was assembled, including antibodies to ALK1, bcl-6, CDs 1alpha, 3, 4, 5, 7, 8, 10, 15, 20, 23, 30, 43, 56, 68, 79alpha, and 99, cyclin D1, EMA, kappa, lambda, LMP1, PAX5, TdT, Vs38C and ZAP70, plus EBER RNA probe by in situ hybridization. The 447 lymphoma cases, subtyped according to the WHO classification, were assembled in triplicate into 11 tissue microarrays and examined with the panel of markers described. Among the 447 cases, 385 (82.6%) were confirmed to be non-Hodgkin lymphomas (NHL) and 62 (13.9%) were Hodgkin lymphomas of classic type (CHL). Of the NHL cases, 68.6% were B-cell lymphomas and 30.6% T/NK-cell lymphomas. Histiocytic neoplasms accounted for only three cases (0.8%). Diffuse large B-cell lymphomas (DLBCL) were the most common subtype (35.1%), followed by peripheral T-cell lymphomas unspecified (PTun, 12.0%), extranodal marginal zone B-cell lymphomas (MALT lymphomas, 11.7%), follicular lymphomas (FL, 8.6%), T-lymphoblastic lymphomas (T-LBL, 7.0%), anaplastic large cell lymphomas (ALCL, 4.2%), B small lymphocytic lymphomas (B SLL, 3.6%), and mantle cell lymphomas (MCL, 2.6%). Of 263 B-cell neoplasms, 105 (39.9%) expressed immunoglobulin light chain, including 52 kappa and 53 lambda, detectable in paraffin sections. The incidence of DLBCL was similar to many Western countries and Asia. The frequency of FL was, however, much lower than the usual pattern in Western countries, although NK/T-cell lymphomas were more common (30.6%), similar to other countries in Asia, including Japan and Korea. With regard to markers of EBV infection, 8 of 385 (2.1%) NHL cases gave positive findings by both in situ hybridization (EBER RNA) and immunohistochemistry (LMP-1), whereas 24 (6.2%) expressed only the EBER and 12 (3.1%) expressed only LMP-1. EBV positivity was found in 24 of 119 (20.2%) T and NK cell lymphomas, in 20 of 263 (7.6%) B cell neoplasms, and in 37 of 62 (59.7%) CHLs. In CHLs there was complete concordance of results by both in situ hybridization (EBER RNA) and immunohistochemistry (LMP-1) procedures. ZAP70 was detected in most T cell-lineage disorders (61.4%) and also in a subset of B small lymphocytic lymphomas (50%). However, ZAP-70 was expressed in a minority of other types of B-cell lymphomas, including precursor B-cell acute lymphoblastic leukemia (25%), diffuse large B-cell lymphoma (26.7%), follicular lymphoma (15.2%), and lymphoplasmacytic lymphoma (9.1%). Immunohistochemical analysis represents an effective method for assessing ZAP-70 expression and reveals that a variety of B-cell malignant neoplasms express ZAP-70, albeit at low frequency.     

Expression of the interleukin-2 receptor (Tac antigen/CD25) in hematologic neoplasms

The expression of interleukin-2 (IL-2) receptor (CD25) has been investigated in 165 cases of hematologic neoplasia by alkaline phosphatase-antialkaline phosphatase (APAAP) labeling of cell smears using two monoclonal anti-IL-2 receptor antibodies (anti-Tac and DAKO-IL2-R). IL-2 receptor was found in 2 of 16 (13%) T-cell malignancies (1 T-ALL, 1 Sézary syndrome). In contrast, among B-cell disorders, IL-2 receptor was expressed in the majority of hairy cell leukemia cases (14 of 16, i.e., 88%) and a smaller proportion of cases of common acute lymphoblastic leukemia (7 of 44, i.e., 16%), B-cell chronic lymphocytic leukemia (8 of 20, i.e., 40%), B-cell prolymphocytic leukemia (3 of 5), and B-cell lymphoma (3 of 8). In addition, IL-2 receptor was present on the neoplastic cells in some cases of acute myeloid leukemia (6 of 44, i.e., 14%) and acute undifferentiated leukemia (4 of 7). IL-2 receptor (Tac antigen) expression is thus found across the spectrum of hematologic neoplasms and is not restricted to T-cell disorders. The explanation for the expression of the IL-2 receptor by such a variety of different hematologic malignancies remains unclear.     

CD200 (OX-2 membrane glycoprotein) expression in b cell-derived neoplasms

We studied the expression of CD200, an immunoglobulin superfamily membrane glycoprotein, in a wide range of B cell-derived neoplasms by immunohistochemical staining of paraffin-embedded tissue sections. In addition to chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL), CD200 is expressed in other B-cell lymphoproliferative disorders, including hairy cell leukemia. In addition, neoplastic cells in classical Hodgkin lymphoma are immunoreactive for CD200. CD200 was previously reported to be expressed in acute myeloid leukemia, and we find that it is also expressed in B-lymphoblastic leukemia/lymphoma. We conclude that CD200 may be a useful immunophenotypic marker in the evaluation of B cell-derived neoplasms. Furthermore, since an anti-CD200 immunotherapeutic agent is in clinical trials, a number of B cell-derived neoplasms in addition to CLL/SLL may be suitable therapeutic targets.     

Utilization of monoclonal antibody L26 in the identification and confirmation of B-cell lymphomas. A sensitive and specific marker applicable to formalin-and B5-fixed, paraffin-embedded tissues.

Immunophenotypic analysis of paraffin-embedded tissues of lymphoproliferative disorders has been facilitated by recent developments of monoclonal antibodies that react with epitopes that survive histologic processing. Leukocyte common antigen (LCA) antibody has made a significant contribution to the immunocytochemical separation of non-Hodgkin's lymphomas from nonlymphoid neoplasms. However, a small percentage of lymphomas, particularly some large cell or immunoblastic B-cell tumors, will not label with LCA antibody. Other antibodies, directed against B lymphocytes, experience problems of specificity and a lack of sensitivity when applied to formalin-fixed specimens. The authors recently investigated a monoclonal antibody (L26) that demonstrates excellent specificity and sensitivity for B lymphocytes, and tumors derived from them, in formalin- and B5-fixed, paraffin-embedded tissue. The avidin-biotin peroxidase complex (ABC) technique was utilized for immunostaining 95 cases of malignant lymphoproliferative disorders and a variety of normal and neoplastic nonlymphoid tissues. When applied to sections of benign lymphoid tissue, the L26 antibody labeled germinal center cells, mantle zone and scattered interfollicular lymphocytes, but not histiocytes or plasma cells. L26 marked 100% (44/44) of the large cell and immunoblastic B-cell lymphomas, along with 1 case of pre-B cell lymphoblastic lymphoma. This included 8 cases that were LCA-negative. None of the T-cell lymphomas or plasma cell tumors studied demonstrated L26 immunostaining. No normal, benign, or neoplastic nonlymphoid tissues examined stained with this antibody. L26 successfully labels B lymphocytes and B-cell lymphomas in routinely processed tissues, often with greater sensitivity and intensity than LCA. This antibody should prove invaluable in the investigation of atypical lymphoid proliferations and the identification of B-cell derived lymphomas, when fresh or frozen tissue is unavailable for analysis.     

Human T-cell malignancies: Correlative clinical, histopathologic, immunologic, and cytochemical analysis of 23 cases.

Twenty-three T-cell neoplasms were investigated for their reactivity with the OKT monoclonal antibodies and expression of certain cytochemical markers. Fourteen neoplasms with diverse histopathologic features, T-cell chronic lymphocytic leukemia, mycosis fungoides, the Sézary syndrome, T-immunoblastic sarcoma, and a pleomorphic large-cell lymphoma, expressed the T helper cell phenotype, OKT3+T4+. Nine other neoplasms displayed marked inter- and intra- tumor heterogeneity. Seven of these cases, lymphoblastic lymphoma, T-cell acute lymphoblastic leukemia, and tumors with feature of T-immunoblastic sarcoma or the multilobated lymphoma of Pinkus, expressed intrathymic phenotypes. The other 2 cases, a lymphoblastic lymphoma and a so-called Lennert's lymphoma, expressed the previously undescribed OKT3+T10+ phenotype. These studies demonstrate that the T-cell malignancies are divisible into phenotypes corresponding to normal maturational stages of T-cell differentiation and functionally distinct T-cell subsets. Such studies should provide a basis for understanding the biologic heterogeneity, clinical diversity, and significance of the variable cytomorphologic characteristics of T-cell malignant tumors and assist in the further delineation of normal human T-cell heterogeneity.     

Aberrant expression of T-cell-associated antigens on B-cell non-Hodgkin lymphomas

We describe 9 well-characterized cases of B-cell non-Hodgkin lymphoma (NHL) that showed aberrant expression of T-cell-associated antigens by 2-color flow cytometry. Cases were as follows: chronic lymphocytic leukemia/small lymphocytic lymphoma, 4; follicle center cell lymphoma, 2; mantle cell lymphoma, 1; and diffuse large B-cell lymphoma, 2. CD2 was the most commonly expressed antigen (5 cases). CD8 and CD7 were identified in 2 cases each, including 1 case that expressed both CD7 and CD4. The disease course and response to treatment were compatible with the type and stage of lymphoma. No unusually aggressive behavior was noted in any case. A control group of 59 cases of benign lymph nodes analyzed during the same period showed no aberrant expression of T-cell-associated antigens; thus, such expression is not a feature of benign lymphoid proliferations. Study of these B-cell lymphomas may prove invaluable to study aberrant activation of silent or repressed T-cell differentiation genes. CD2-expressing B-cell NHLs may represent clonal expansion of CD2+ B lymphocytes that normally constitute a small fraction of peripheral B lymphocytes and should not be confused with composite B- and T-cell lymphomas. Unless aggressive behavior is noted consistently, no aggressive treatment is justified.     

The expression of CD22 (Leu 14) and CD11c (LeuM5) in chronic lymphoproliferative disorders using two-color flow cytometric analysis

The monoclonal antibodies (MoAbs) CD22 and CD11c recognize B-lymphocyte- and monocyte-associated antigens, respectively. Reports indicate that when these two MoAbs co-express, they represent a unique marker for hairy cell leukemia (HCL) although neither is specific for that disease. The authors evaluated the expression and diagnostic utility of CD22 and CD11C in specimens from 26 normal subjects, 29 patients, with various nonlymphoproliferative disorders (NLPDs), and 75 patients with different types of chronic lymphoproliferative disorders (CLDs) using two-color flow cytometric analysis of peripheral blood lymphocytes. Lymphocytes co-expressed CD22 and CD11c in less than or equal to 3% of the normal subjects and in less than or equal to 6% of the patients with NLPDs. These markers were expressed in greater than 10% of the lymphocytes of 46% (32/69) of the patients with B-cell CLDs: B-cell chronic-lymphocytic leukemia, 9/41; B-cell non-Hodgkin's lymphoma, 8/14; HCL, 11/11; B-cell lymphoproliferative disorder (NOS), 1/2; and B-cell prolymphocytic leukemia, 1/1. None (0/6) of the lymphocytes of patients with T-cell CLDs expressed greater than 10% CD22-positive (CD22+) or CD11c-positive (CD11c+) cells. The HCL cases demonstrated a unique CD22+CD11c+ fluorescence histogram pattern, distinct from other lymphoproliferative disorders, that was characterized by uniformly intense CD11c and CD22 fluorescence. Differences in the expression of the CD22+CD11C- and CD22+CD11C+ phenotypes between diagnostic groups were found, most notable was a paucity of CD22+CD11c+ cells in lymphocytes of patients with HCL. CD22 also had more variable expression than CD19 and HLA-DR in the cases of B-cell CLD. This study demonstrates that the CD22+CD11c+ phenotype is not unique to HCL but is a consistent feature of that disorder and that the immunofluorescence pattern of co-expression in HCL is diagnostically useful.     

Lack of surface immunoglobulin light chain expression by flow cytometric immunophenotyping can help diagnose peripheral B-cell lymphoma

We determined the prevalence and significance of finding B cells without surface immunoglobulin (SIg) light chain expression. The flow cytometry database at Johns Hopkins Medical Institutions was searched for cases in which immunoglobulin light chain staining was performed to rule out a B-cell malignant neoplasm between January 1994 and February 2000. We excluded plasma cell dyscrasias, precursor B-cell acute lymphoblastic leukemia/lymphomas, and hematogones. Cases with more than 25% of B cells lacking SIg light chain expression were retrieved. Polymerase chain reaction assays for immunoglobulin heavy chain gene rearrangements were performed in SIg-negative cases with available tissue blocks. We identified 36 cases; all represented lymphoma. Their diagnoses included diffuse large B-cell lymphoma (20), HIV-related lymphoma (5), follicular lymphoma (5), Burkitt lymphoma (2), monomorphic posttransplant lymphoproliferative disorder (1), chronic lymphocytic leukemia/small lymphocytic lymphoma (1), marginal zone B-cell lymphoma (1), and low grade B-cell lymphoma (1). Of the 17 SIg-negative cases with amplifiable DNAs, 12 (71%) showed a clonal immunoglobulin heavy chain gene rearrangement. SIg-negative B-cell lymphomas are rare. Complete absence of SIg light chain expression in a mature B cell proliferation can be used as a surrogate marker to help diagnose peripheral B-cell lymphoma.