Coexpression of epithelial membrane antigen (EMA), Ki-1, and interleukin-2 receptor by anaplastic large cell lymphomas. Diagnostic value in so-called malignant histiocytosis

A group of 63 cases of anaplastic large cell lymphomas (variants of diffuse large cell lymphomas often diagnosed as "malignant histiocytosis") was characterized on both morphologic criteria and expression of epithelial membrane antigen (EMA) and Ki-1 antigen (CD30). On the basis of the reactivity of these tumors with anti-EMA and anti-Ki-1 antibodies, four subtypes could be distinguished. In the majority of cases (n = 49), neoplastic cells coexpressed EMA and Ki-1 antigens. Nineteen of these cases were tested for IL-2R, and all were positive (Type I, EMA+, Ki-1+, IL-2R+). In the second group (n = 5), the neoplastic cells expressed EMA but not the Ki-1 antigen. These cases were not tested for the presence of IL-2R (Type II, EMA+, Ki-1-, IL-2R?). There were tumors with similar morphology expressing only Ki-1 antigen (Type III, EMA-, Ki-1+, IL-2R-) or negative for both EMA and Ki-1 antigens (Type IV, EMA-, Ki-1-, IL-2R-). EMA appeared to occur predominantly on activated cells, as has been previously shown for Ki-1 antigen. Analysis using monoclonal antibodies to T-cell, B-cell, or macrophage-associated differentiation antigens showed that these tumors were heterogeneous in terms of cell lineage. Tumors coexpressing EMA, Ki-1, and IL-2R (Type I), were most commonly of T-cell origin (n = 12); the remainder in this type expressed B-cell markers (n = 4), a mixed B/T phenotype (n = 2), or no clear phenotype (n = 9). By contrast, tumors of Types II, III, and IV were mainly from B-cell origin (n = 6) or showed a mixed B/T phenotype (n = 1). Despite the fact that a significant proportion of these cases were initially classified morphologically as "malignant histiocytosis," only 3 of the 63 cases were possibly of histiocytic origin. These results confirm that true malignant histiocytosis is rare and that most tumors with histologic features currently regarded as being consistent with this diagnosis are lymphocytic in origin and express activation antigens such as EMA, Ki-1 antigen, and IL-2R.     

CD26/dipeptidyl peptidase IV expression in human lymphomas is restricted to CD30-positive anaplastic large cell and a subset of T-cell non-Hodgkin's lymphomas

CD26 is identical to the cell surface ectoenzyme dipeptidyl peptidase IV (DPPIV). is associated with T-cell activation and proliferation and also may function as an auxiliary adhesion factor. Although has been previously studied on lymphoid populations and on leukemias/lymphomas of B- and T-cell phenotype, little is known about its expression and functional role in some specific types of lymphomas, such as CD30-positive anaplastic large cell (ALC) lymphomas and Hodgkin's disease (HD). A series of 81 lymphoma samples, including 23 cases of HD, 17 cases of CD30-positive ALC lymphomas, 41 cases of other non-Hodgkin's lymphomas (NHL), and a panel of HD- or ALC lymphoma-derived human cell lines were evaluated for expression by enzyme histochemistry and immunohistochemistry on frozen sections and cell smears. protein was expressed on neoplastic cells in 12 of 17 (71%) ALC lymphomas irrespective of their antigenic phenotype and in seven of 15 (47%) T-cell NHLs. In contrast, we did not detect expression in tumor cells from 26 cases of B-cell NHL other than ALC lymphomas or in Reed Sternberg (RS) cells and variants of 21 of 23 HD cases. Accordingly, expression was maintained on the CD30-positive ALC lymphoma cell line Karpas 299, but the molecule was not detected on HD-derived cell lines of B, T, or non-B non-T phenotype. These results may support a new potential tool for the phenotypic separation of ALC lymphomas from HD based on the differential expression of the molecule. Moreover, given the demonstration that is identical to the human adenosine deaminase (ADA) binding protein, it could be speculated that also may function by interacting with ADA to regulate the growth of expressing neoplastic cells in ALC lymphomas.     

The expression of the B-cell marker mb-1 (CD79a) in Hodgkin's disease

Recent evidence indicates that membrane-bound immunoglobulin on B lymphocytes is associated with a molecule which comprises the products of the mb-1 and B29 genes. This molecule is a highly specific marker for B-cells, presumably because of its central functional role in antigen triggering, and has recently been clustered as CD79a at the 5th Leucocyte Workshop. Recently there has been controversy surrounding reports of B-cell antigen expression by Reed–Sternberg and related cells, and we have therefore studied 108 cases of Hodgkin's disease immunohistochemically using a novel antibody which detects mb-1 protein in paraffin sections. The results were compared with those achieved using antibody L26 to detect CD20. The mb-1 protein was present in the neoplastic cells in all 14 cases of lymphocyte predominance Hodgkin's disease studied, and CD20 immunoreactivity was also found in seven of the eight cases of this subtype studied. Of the non-lymphocyte predominance cases, 20% (19/94) expressed mb-1 and 30% (20/67) CD20 in the Reed–Sternberg cells, but the cells positive for either of these two markers usually constituted only a very small proportion of the neoplastic population. However, in occasional cases (one of 94 for mb-1 and five of 67 for CD20), more than 50% of the neoplastic cells expressed one or both B-cell antigens. These results confirm the B-cell origin of the neoplastic cells in lymphocyte predominance Hodgkin's disease, but they also indicate that, contrary to our previous study, mb-1 expression may occasionally be found in what appears, on histological grounds, to be other types of Hodgkin's disease.     

Immunohistochemical and immunoelectron microscopic studies of the localization of KL-6 and epithelial membrane antigen (EMA) in presumably normal pulmonary tissue and in interstitial pneumonia

To clarify the localization of KL-6 and epithelial membrane antigen (EMA) in human lungs, immune reactions to antibodies to these factors were examined in detail at light and electron microscopic levels. Immunohistochemical investigation was performed in 17 cases of usual interstitial pneumonia (UIP), nonspecific interstitial pneumonia (NSIP), hypersensitivity pneumonitis (HP), collagen vascular disease-associated interstitial pneumonias (CVD-IP), viral pneumonia, and bronchobronchioloectasis, as well as in 10 cases of presumably normal pulmonary tissue resected as a result of spontaneous pneumothorax. Immunohistochemical study revealed similar discontinuous linear or dome-shaped positive patterns restricted to type II alveolar cells in presumably normal tissue and only some regions of interstitial pneumonia. In sharp contrast, immune reactions with each of the two antibodies yielded a continuous linear pattern surrounding damaged areas in most regions of interstitial pneumonias and some normal areas as well. Staining for EMA antibody was negative in some regenerating alveolar and bronchial cells in regenerating foci in interstitial pneumonias, although staining for KL-6 antibody was always positive in these cells. Immunoelectron microscopic studies demonstrated similar positive reactions with both antibodies on the surface of alveolar epithelial cells in three of the cases examined, with surface positive granules 100–200 nm in diameter. Thus, although staining for both KL-6 and EMA antibodies exhibited discontinuous positivity restricted to type II alveolar cells in nondamaged regions, immune reactions were continuous and linear in pattern in or around damaged areas of the lungs at both light and electron microscopic levels, probably as a consequence of cell-surface barrier function. These findings in pulmonary tissue might be evidence of defense functions.     

Differential expression of the HECA-452 antigen (cutaneous lymphocyte associated antigen, CLA) in cutaneous and non-cutaneous T-cell lymphomas

The monoclonal antibody HECA-452 identifies an antigen that is primarily expressed on high endothelial venules, the preferred site of lymphocyte extravasation in lymphoid tissues, and also on a subpopulation of myelomonocytic cells and some T-cells. We investigated the expression of the HECA-452 antigen, also called the cutaneous lymphocyte associated antigen, in primary cutaneous and primary non-cutaneous T-cell non-Hodgkin's lymphomas. The tumour cells of cutaneous T-cell non-Hodgkin's lymphomas were positive in 53% of cases, while only 5% of the non-cutaneous lymphomas were positive. These differences were also present in morphologically identical tumours. Thus, the tumour cells in six out of 10 primary cutaneous anaplastic large cell T-cell lymphomas were positive, while they were positive in none of 24 primary non-cutaneous anaplastic large cell T-cell lymphomas. In general, primary cutaneous and primary nasal T-cell non-Hodgkin's lymphomas were devoid of HECA-452 positive high endothelial venules, whereas most nodal T-cell non-Hodgkin's lymphomas contained HECA-452 positive high endothelial venules. These observations suggest that the HECA-452 antigen might be related to a skin-associated type of lymphoid tissue and to lymphomas originating in the skin. However, the results of HECA-452 expression in secondary sites, and the clinical data of the primary cutaneous large cell lymphomas did not support the concept that HECA-452 is functionally involved in homing to the skin, or that loss of the HECA-452 antigen is related to tumour progression of primary cutaneous T-cell lymphomas.(ABSTRACT TRUNCATED AT 250 WORDS)     

Usefulness of epithelial membrane antigen (EMA) to discriminate between perineural invasion and perineural indentation in prostatic carcinoma

AIMS: Perineural invasion (PNI) is one of the few unequivocal criteria to diagnose adenocarcinoma of the prostate. Distinguishing PNI from perineural indentation (PNIn), however, is sometimes difficult. The aim of this study was to discriminate between PNI and PNIn using EMA immunohistochemistry. METHODS AND RESULTS: We selected representative sections from 87 prostatectomies with prostatic adenocarcinoma. Normal peripheral nerves were continuously encircled with perineurium, which was immunoreactive for EMA. We identified 1319 PNI by carcinomas, 368 PNIn by carcinomas, and 303 PNIn by benign glands. We categorized the EMA immunoreactivity patterns into three classes: samples that displayed discontinuity or complete loss of the perineurium (Type A), samples where there were carcinomas or benign glands in the perineural space or peripheral nerves (Type B) and samples that showed no changes in the perineurium (Type C). For PNI we observed Type A, Type B, and Type C patterns in 55.3%, 24.8% and 19.9% of carcinomas, respectively. The incidence of each of those patterns in PNIn by carcinomas was 32.1%, 14.9% and 53.0%, respectively. Cases of PNIn by benign glands showed Type A or Type C patterns. They did not, however, exhibit Type B patterns. CONCLUSION: EMA immunostaining will aid the diagnosis of prostatic adenocarcinoma.     

Expression of nestin, mesothelin and epithelial membrane antigen (EMA) in developing and adult human meninges and meningiomas

The spatial and temporal pattern of appearance of nestin, epithelial membrane antigen (EMA) and mesothelin proteins was immunohistochemically determined in the cells of normal developing and adult human meninges and meningiomas. Human meninges developed as two mesenchymal condensations in the head region. The simple squamous epithelium on the surface of leptomeninges developed during mesenchymal to epithelial transformation. Nestin appeared for the first time in week 7, EMA in week 8, while mesothelin appeared in week 22 of development. In the late fetal period and after birth, nestin expression decreased, whereas expression of EMA and mesothelin increased. EMA appeared in all surface epithelial cells and nodules, while mesothelin was found only in some of them. In adult meninges, all three proteins were predominantly localized in the surface epithelium and meningeal nodules. In meningothelial meningiomas (WHO grade I), EMA was detected in all tumor cells except in the endothelial cells, mesothelin characterized nests of tumor cells, while nestin was found predominantly in the walls of blood vessels. The distribution pattern of those proteins in normal meningeal and tumor cells indicates that nestin might characterize immature cells, while EMA and mesothelin appeared in maturing epithelial cells. Neoplastic transformation of these specific cell lineages contributes to the cell population in meningiomas.     

Immunolocalization of nestin, mesothelin and epithelial membrane antigen (EMA) in developing and adult serous membranes and mesotheliomas

The spatial and temporal distribution of epithelial membrane antigen (EMA), mesothelin and nestin was immunohistochemically analyzed in developing and adult human serous membranes and mesotheliomas in order to detect possible differences in the course of mesenchymal to epithelial transformation, which is associated with differentiation of mesothelial cells during normal development and tumorigenesis. Pleura and pericardium developing from the visceral mesoderm gradually transform into mesothelial cells and connective tissue. EMA appeared in mesothelium of both serous membranes during the early fetal period, whereas during further development, EMA expression was retained only in the pericardial mesothelium. It increased in both pleural mesothelium and connective tissue. Mesothelin appeared first in pericardial submesothelial cells and later in surface mesothelium, while in pleura it was immediately localized in mesothelium. In adult serous membranes, EMA and mesothelin were predominantly expressed in mesothelium. Nestin never appeared in mesothelium, but in connective tissues and myocardial cells and subsequently decreased during development, apart from in the walls of blood vessels. Mesothelial cells in the two serous membranes developed in two separate developmental pathways. We speculate that submesothelial pericardial and mesothelial pleural cells might belong to a population of stem cells. In epithelioid mesotheliomas, 13% of cells expressed nestin, 39% EMA and 7% mesothelin.     

Epithelial markers in primary skin cancer: an immunoperoxidase study of the distribution of epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA) in 65 primary skin carcinomas

Sixty-five primary malignant skin tumours have been stained for carcinoembryonic antigen (CEA) and epithelial membrane antigen (EMA) using rabbit polyclonal affinity-purified antibodies and an indirect immunoperoxidase technique. The tumours consisted of 15 invasive squamous carcinomas, 23 basal cell carcinomas, 16 malignant eccrine poromas (porocarcinomas), and 11 sebaceous carcinomas. The basal cell carcinomas were negative for CEA and EMA except where there was keratotic or sebaceous differentiation. All the sebaceous and squamous carcinomas and 15/16 porocarcinomas contained EMA. 12/15 squamous carcinomas were positive for CEA. The malignant poromas were negative for CEA except on the ulcerated surface of two. In tumours classified as sebaceous carcinomas there was positive staining for CEA in some cells, cyst contents and/or keratotic foci. These findings have implications for the use of immunoperoxidase localization of epithelial markers in the differential diagnosis of primary and metastatic skin cancer.     

鼻咽癌高发区何杰金病EB病毒DNA及潜伏感染膜蛋白检测的意义

为检测鼻咽癌高发区何杰金病中爱泼斯坦-巴尔病毒（EBV）DNA及其表达产物──潜伏感染膜蛋白的存在及探讨其意义，采用热启动聚合酶链反应（PCR）及LSAB免疫组化法结合微波处理技术，检测了选自鼻咽癌高发区的40例何杰金病、20例淋巴结良性病变存档标本中的EBVDNA和潜伏感染膜蛋白（LMP1）。结果显示：65％的何杰金病中EBVDNA阳性，淋巴结良性病变中的阳性率也达50．0％（10例／20例），两者差异无显著性（P＜0．05）。LMP1只在何杰金病肿瘤细胞中表达，其检出率为52．5％（21例／40例）。20岁以下何杰金病中EBVDNA和LMP1的检出率分别为84．6％（11例／13例）和76．9％（10例／13例），皆明显高于20岁以上年龄组（分别为14例／25例，56．0％和10例／25例，40．0％）P＜0．05。本结果表明：鼻咽癌高发区半数以上何杰金病肿瘤细胞中有EBV潜伏感染，并可能在肿瘤的发生发展中起着一定的作用。提示青少年何杰金病和EBV潜伏感染并表达LMP1的关系更为密切。     

Definition of the Variables Affecting Efficacy of Immunodepletion Ex Vivo of Peripheral Blood Progenitor Cell Grafts by Alemtuzumab (Campath in the Bag)

The immunodepleting effects of alemtuzumab on peripheral blood progenitor cell (PBPC) grafts for stem cell transplantation need to be better defined. The optimal graft cell concentration, antibody dose, need for complement, and whether alemtuzumab is infused with the graft during transplantation remain unclear. PBPC from 6 normal allogeneic stem cell donors harvested by apheresis were first quantitated and the cellular content defined by flow cytometry. Mononuclear cells were then incubated with incremental concentrations of alemtuzumab (.00001, .0001, .001, and .01 mg/mL) for 30 minutes at 20°C or in cell dose responses with 1, 5, and 10 × 10⁶ mononuclear cells/mL added to a fixed dose of .001 mg/mL of alemtuzumab with or without a source of complement. Cells were enumerated and analyzed by flow cytometry before and after exposure to alemtuzumab. To determine the presence of unbound anti-CD52, the supernatant of the cell dose responses were tested using the ELISA assay. Selected CD34+ lineage-negative cells were incubated with antibody at the same working concentrations and conditions and cultured in granulocyte-macrophage colony-forming unit assay. The colony numbers were compared with control cultures devoid of the antibody. Incremental concentrations of alemtuzumab led to a significant (2 log) reduction in CD3, CD4, and CD8 populations, which plateaued at .001 mg/mL. Addition of complement led to a further significant reduction in the CD4 and CD8 cells. The maximum CD4 (3 log) and CD8 (2 log) cell death was obtained at 10 × 10⁶ cells/mL. Analysis of supernatants for soluble alemtuzumab by ELISA showed a significant reduction in the free antibody concentration when the cell number was increased from 1 to 10 × 10⁶ cells/mL implying utilization/binding of the antibody by target cells. Incremental concentrations of alemtuzumab did not affect the number of granulocyte-macrophage colony-forming units. Alemtuzumab depletes all cells expressing the CD52 antigen and has higher activity on CD3, CD8, and particularly on CD4 cells, which are depleted in excess of 2 logs. From this study, we were able to derive that the optimal cell kill in the graft without detectable free alemtuzumab in the supernatant can be achieved with 1 mg of antibody per 100 mL containing 10 × 10⁹ cells and active complement (AB serum).     

Immunohistochemical detection of cytokeratin and epithelial membrane antigen in leiomyosarcoma: a systematic study of 100 cases

Although 'aberrant' expression of the epithelial markers, cytokeratin (CK) and epithelial membrane antigen (EMA), in leiomyosarcoma has been described previously, there has not been a study of this phenomenon with clinicopathological correlation in a large series of lesions at different anatomical sites. We investigated systematically the immunohistochemical reactivity for CK and EMA in 100 cases of leiomyosarcoma. CK and EMA were positive in 38% and 44% of the cases, respectively. Although staining was usually focal, extensive immunoreactivity was observed in 11% with CK and 6% with EMA. There was no correlation between immunoreactivity for CK and EMA in leiomyosarcomas and non-neoplastic smooth muscle at the same location. Immunoreactivity for CK and EMA was not correlated with the location, age, sex, histological grade, or histological features, except for more frequent EMA positivity in vascular and uterine tumors than in soft tissue cases. These results indicate that CK and/or EMA-positive leiomyosarcomas do not have distinctive clinicopathological features differing from those of negative cases. However, the considerable frequency of immunoreactivity for these epithelial markers in leiomyosarcoma, occasionally with diffuse and strong immunopositivity, should be recognized as a potentially serious diagnostic pitfall in the differential diagnosis of other malignant spindle cell neoplasms.     

Expression of the Ig-associated heterodimer (mb-1 and B29) in Hodgkin's disease

Eighty-three cases of Hodgkin's disease were studied immunocytochemically for the presence of the Ig associated heterodimer (mb-1 and B29) which is believed to be a specific pan B-cell marker. These results were compared with those achieved using other B-cell markers against CD19, CD20 and CD22. Although a small number of cases of nodular sclerosis and mixed cellularity subtype showed positivity for CD19, CD20 or CD22, no case showed any reactivity with antibodies against mb-1 or B29. This contrasted markedly with the cases of lymphocyte predominance where all seven cases expressed one or more of the B-cell antigens, with six cases being positive for mb-1. These results confirm previous studies that have suggested lymphocyte-predominance Hodgkin's disease is of B-cell origin and different from the other subtypes. However, they do not provide support for the thesis that these other subtypes may also have a B-cell origin, albeit with a different phenotype to lymphocyte predominance.     

FU-3 monoclonal antibody: a specific marker for malignant fibrous histiocytoma? An analysis of 32 malignant soft tissue and bone sarcomas

An immunohistochemical study on frozen sections was carried out on 51 malignant tumours of soft tissue and bone using the FU-3 monoclonal antibody. This antibody is claimed to be specific for malignant fibrous histiocytoma (MFH) and liposarcoma and for normal and tumour cells located in perivascular fields. The results show a lack of specificity in MFH staining: several malignant tumours such as synovial sarcoma, fibrosarcoma, rhabdomyosarcoma, osteogenic sarcoma, and including an anaplastic malignant melanoma, presented positive staining somewhat similar to that found in MFH. The value of this antibody in the differential diagnosis of MFH is doubtful. It might be useful to recognize a common pathway of terminal differentiation expressed by several pleomorphic sarcomatous neoplasms.This paper was presented in a short form at the XIX International Congress of the International Academy of Pathology, Madrid (18–23 October 1992).     

Immunohistochemical staining of non-Hodgkin's lymphoma in paraffin sections using the MB1 and MT1 monoclonal antibodies

We have performed a single blind trial to assess the value of the monoclonal antibodies MB1 and MT1 in lymphoma classification. Sixty cases of non-Hodgkin's lymphoma (NHL) were stained with MB1 and MT1 using an indirect immunoperoxidase technique in paraffin sections. The majority of B tumours (27/33) stained with MB1, and most of the T tumours (24/27) stained with MT1. The MB1 antibody often produced rather weak staining but it was apparently highly specific for B cells, with only three (3/27) of the T tumours (two cases of 'malignant histiocytosis' of the intestine (MHI) and one pleomorphic T-cell lymphoma) displaying 'false' positivity. The MT1 antibody generally produced very strong staining, but it was not very selective, with 14/33 of the B lymphomas displaying 'false' positivity. the cross-reactivity observed in 17 cases led to only three misdiagnoses, two B tumours being designated as T lymphomas and one T tumour being designated as a B lymphoma. In a few cases (7/17), dual staining with both antibodies precluded firm diagnosis. In other cases (6/17), classification was possible despite some of the tumour cells showing dual staining. The seventeenth case was a plasmacytoma displaying MT1 positivity only. While the monoclonal antibodies MB1 and MT1 are of use in classifying lymphomas in paraffin section, they are not entirely lineage-specific, and the uncritical use of these two reagents alone may give rise to misdiagnosis; the use of a panel of monoclonal antibodies may yield more accurate results. As with any immunohistochemical marker, their limitations should be recognized; interpretation must be judicious and always in the context of the histological appearances.     

Reticulin fibre content of bone marrow infiltrates of malignant non-Hodgkin's lymphomas (B-cell type,low malignancy) — a morphometric evaluation before and after therapy

Summary A morphometric study was performed on bone marrow infiltrates of non-Hodgkin's lymphomas (B-cell type, low malignancy) to evaluate the content of argyrophilic (reticulin) fibres in the various subtypes before and after therapy. In congruence with the corresponding lymph node lesions, subtypes consisted of lymphocytic lymphoma — chronic lymphocytic leukaemia (CLL,n = 39), centroblastic-centrocytic lymphoma (CB-CC,n = 35), lymphoplasmacytoid immunocytoma (LPI,n = 22) and finally hairy cell leukaemia (HCL,n = 21). In comparison with control specimens, morphometric measurements on trephine biopsies (initial staging procedure) disclosed a borderline or minimal increase in reticulin in CLL and moderate fibrosis in CB-CC and LPI, whereas HCL had the greatest increase in fibres. The marrow surrounding focal or patchy lymphoma infiltrates of CLL and CB-CC displayed no relevant changes in fibre density with respect to the control samples. Following chemotherapy, repeated trephine biopsies (restaging procedure) were obtainable from 38 patients. There was no significant decrease in the fibre content of CLL, CB-CC and LPI infiltrates. In HCL an incomplete reduction was recorded after interferon treatment. So-called benign lymphoid lesions may be distinguished from focal-patchy infiltrates of CB-CC and LPI not only by showing a central localization, but also by the absence of significant amounts of reticulin. However, considering the density of the reticulin fibres, a clear-cut discrimination of these lymphoid aggregates from an early nodal-central growth pattern of CLL is not feasible in many cases.     

Rare expression of KIT (CD117) in lymphomas: a tissue microarray study of 1166 cases

AIMS: Imatinib mesylate specifically inhibits KIT tyrosine kinase activity, and has been proven to be effective in the treatment of gastrointestinal stromal tumours. Because other KIT-expressing malignancies might benefit from Imatinib therapy, we evaluated the distribution and expression of KIT in 1166 cases of malignant lymphoma. MATERIALS AND RESULTS: Tissue microarrays (TMAs) containing 824 non-Hodgkin's lymphoma (NHL) and 342 Hodgkin's lymphoma (HL) cases were immunohistochemically analysed for the expression of the KIT protein. Two KIT-positive NHLs were sequenced using polymerase chain reaction analysis. One T-cell lymphoma and one follicular lymphoma of the 747 NHL cases (0.3%) were positive for KIT. All HLs were Kit-negative. None of the KIT-positive cases showed a kit gene mutation. CONCLUSIONS: KIT expression is a very rare event in NHL and virtually absent in HL. In the few positive cases, the aberrant expression is not caused by a mutation in the 'hot-spots' of the kit gene, indicating that treatment of these tumours with Imatinib may be ineffective.     

Idiotypic cascade in the human high molecular weight melanoma-associated antigen system: Fine specificity and idiotypic profile of anti-anti-idiotypic monoclonal antibodies

The mouse anti-idiotypic (anti-id) monoclonal antibody (mAb) MK2–23 bears the internal image of the determinant defined by the syngeneic immunizing anti-human high molecular weight melanoma-associated antigen (HMW-MAA) mAb 763.74, since it induces anti-HMW-MAA antibodies in syngeneic and xenogeneic hosts. To dissect the humoral immune response induced by mAb MK2–23 at the clonal level, 1351 hybridomas were generated from a BALB/c mouse immunized with mAb MK2–23. Serological and immunochemical assays showed that the anti-anti-idiotypic (anti-anti-id) mAb GH827, GH1002 and GH1081 react only with the immunizing anti-id mAb MK2–23 and that the anti-anti-id mAb GH149, GH368, GH464, GH518, GH586, GH704, GH786 and GH1151 react with both mAb MK2–23 and HMW-MAA. The eight HMW-MAA binding anti-anti-id mAb resembled mAb 763.74 in their reactivity patterns with a panel of cell lines, although the extent of reactivity was lower. Staining of surgically removed melanoma lesions detected subtle differences in the reactivity patterns of the eight HMW-MAA binding anti-anti-id mAb. This finding in conjunction with the differential ability of the eight anti-anti-id mAb to inhibit the binding of anti-HMW-MAA mAb 763.74 to melanoma cells and to mAb MK2–23 and with the different avidity of the binding to mAb MK2–23 suggest diversity in the fine specificity of the eight HMW-MAA binding anti-anti-id mAb. Like mAb 763.74, the eight HMW-MAA binding anti-anti-id mAb express the idiotopes recognized by the anti-id mAb MK2–23 and MK2-120. In contrast, the three anti-anti-id mAb GH827, GH1002 and GH1081, which do not bind HMW-MAA binding anti-anti-id mAb to the antibodies elicited by the membrane-bound HMW-MAA corroborates the validity of the use of anti-id mAb MK2-23 as an immunogen to implement active specific immunotherapy in patients with malignant melanoma.     

The expression of the EBV latent membrane protein (LMP-1) is independent of CD23 and bcl-2 in Reed-Sternberg cells in Hodgkin''s disease

A series of 33 cases of Hodgkin's disease was investigated for the presence of the EBV encoded latent gene product LMP-1 and of CD23 using immunohistochemical techniques. The expression of bcl-2 was examined in a subset of cases. LMP-1 was detected in the Reed-Sternberg cells in 15 cases. Although LMP-1 is known to upregulate CD23 and bcl-2, there was no correlation between the expression of LMP-1 and the detection of CD23 and bcl-2 in Reed-Sternberg cells.     

Epitopic Heterogeneity of the CD36 Antigen Expressed by Normal and Neoplastic Endothelial Cells: An Immunohistochemical Study with a Novel Monoclonal Antibody 8C9

Phenotypic and functional heterogeneity of endothelial cells (ECs) is being recognized with increasing frequency. Here we report a novel murine monoclonal antibody (MoAb), named 8C9, that detects a unique epitope on the leukocyte differentiation antigen CD36 (platelet glyco-protein IV or Illb) expressed by both normal and neoplastic ECs. In immunohistochemical and flow cytometric studies, 8C9 immunoreactivity was detected on capillary ECs, adipocytes, monocytes, platelets and a human monocytoid cell line U 937, which are known to express the CD36 antigen. Blocking experiments using U -937 cells and studies on cryostat sections revealed that a murine MoAb OKM5, which detects the CD36 antigen, blocked the binding of 8C9 to its antigen. lmmunoblot analysis showed that 8C9 bound to a 97-kDa membrane protein expressed by U 937 cells treated with phorbol ester. These results indicate that 8C9 detects the CD36 antigen. However, the findings that some OKMS- positive normal ECs in the liver, spleen and lymph nodes as well as neoplastic ECs in a cutaneous angiosarcoma did not react with 8C9, together with the fact that the CD36 antigen does not form a complex or associate with other proteins, suggest epitopic heterogeneity of the CD36 antigen expressed by these tissues. Acta Pathol Jpn 42: 807–817, 1992.