Expression of the bcl-2 oncogene protein is not specific for the 14;18 chromosomal translocation

It has been reported previously that the bcl-2 protooncogene protein is detectable in neoplastic cells from cases of human lymphoma in which the 14;18 chromosomal translocation is present, but not in lymphomas that lack this chromosomal rearrangement or in normal lymphoid tissue. In the present study we confirmed, by immunohistologic labeling with polyclonal and monoclonal antibodies, that bcl-2 protein is strongly expressed in many cases of follicular lymphoma and that these neoplastic follicles differ clearly from their nonmalignant counterpart (reactive germinal centres) in which bcl-2 protein is undetectable. However we also found bcl-2 protein in normal T- and B-lymphoid cells and in a variety of lymphoproliferative disorders in which the 14;18 translocation is not present. It is therefore concluded that expression of bcl-2 protein is not a specific marker for lymphomas bearing the 14;18 chromosomal translocation and that the observations of other investigators may have reflected the inadequate sensitivity of their staining procedure.

Malignant histiocytosis. A reassessment of cases previously reported in 1975 based on paraffin section immunophenotyping studies

Malignant histiocytosis (MH) is a term that has been used to describe a syndrome in which there is a systemic proliferation of cells that have the cytologic appearance of atypical histiocytes. Biopsy materials from 15 patients with malignant lymphoma diagnosed as malignant histiocytosis in a previous study reported in 1975 were analyzed by a panel of antibodies and reclassified using current nosologic concepts of malignant lymphoma. The antibodies used comprised reagents detecting a formalin-resistant epitope on B-cells (L26), T-cells (anti-CD3, anti-leu 22 [CD43], and UCHL1 [CD45RO]), monocyte/macrophage-derived cells (KP1 [CD68]), as well as antibodies that detect leukocyte common antigen (PD7 [CD45RB]), and a formalin-resistant epitope of Ki-1 (Ber-H2 [CD30]). The authors found that nine lymphomas had a profile consistent with T-lineage, including six in which Ki-1 (CD30) was coexpressed, and two were B-lineage. Three lymphomas showed no specific lineage characteristics although two were Ki-1 (CD30) positive, and none had expression of KP1 (CD68). The 12 lymph node biopsy specimens showed a variety of patterns of involvement, including sinusoidal, paracortical, and diffuse; the spleens showed predominantly red pulp involvement. A 15th case was believed most consistent with a virus-associated hemophagocytic syndrome. These findings support previous suggestions that the majority of cases diagnosed as MH represent T-lineage-associated hematolymphoid neoplasms, and that only a rare case will be of monocyte/macrophage origin. It is suggested that the term MH be subsumed under the rubric of large cell lymphoma and unless there are compelling immunohistochemical data to support a histiocytic origin, that the term MH be abandoned in favor of a more accurate descriptive term, such as sinusoidal large cell lymphoma.

Megakaryocytes in myelodysplasia: an immunohistochemical study on bone marrow trephines

Megakaryocytes in 63 bone marrow trephine biopsies were examined for their staining characteristics, location and size distribution using the monoclonal antibody Y2/51 directed against platelet glycoprotein IIIa (CD61). Megakaryocytes in normal bone marrow were evenly distributed and demonstrated homogeneous staining with Y2/51. In addition, there was little variation in their size or shape. In contrast, myelodysplastic and myeloproliferative bone marrow trephines showed considerable dysmegakaryopoiesis demonstrated by heterogeneity of staining, an altered architectural distribution with a predominantly paratrabecular location and considerable variation in size and shape. Furthermore, in myelodysplasia 25% of the CD61 positive cells were micromegakaryocytes as opposed to less than 10% in normal or reactive marrows. Such dysmegakaryopoiesis is believed to be a clinically important feature of myelodysplasia, although until now it has only been possible to assess it subjectively. The availability of the monoclonal antibody Y2/51 provides a rapid and reproducible means of studying megakaryocyte size, shape and distribution in routine trephine specimens and may help to overcome some of the diagnostic problems currently associated with myelodysplasia and other intrinsic bone marrow neoplasias.

Additional evidence that "plasmacytoid T-cell lymphoma" associated with chronic myeloproliferative disorders is of macrophage/monocyte origin

Plasmacytoid T-cell lymphoma (PTL) is a rare lymphoma with unique morphologic, immunologic, and clinical features. Thus far, only three cases have been reported, each terminating in myeloid leukemia. The macrophage/monocyte rather than T-cell origin of "plasmacytoid T-cells" in reactive lymph nodes has been suggested in the past, but there has been no extensive investigation to demonstrate whether the PTLs are also of this lineage. The authors now report on a patient with PTL who had a long history of clinically stable idiopathic myelofibrosis. Immunocytochemical staining of the neoplastic plasmacytoid cells, with a large panel of monoclonal antibodies used on fresh-frozen and paraffin-embedded tissue sections, showed that the neoplastic cells expressed several macrophage/monocyte-associated markers, i.e., CD31, CD36 (thrombospondin receptor), and CD68 (KP1). Other markers of the macrophage/monocyte lineage (e.g., CD11b, CD11c, CD16) were absent. The neoplastic cells lacked B-cell-associated antigens and lacked most T-cell-associated markers, with the exception of CD2 and CD4. These findings are in close agreement with those of previous studies on normal plasmacytoid T-cells and support the macrophage/monocytic origin of PTL. Molecular hybridization studies provided additional support for the nonlymphoid origin of the plasmacytoid cells by demonstrating the absence of T-cell-receptor beta-chain and immunoglobulin heavy-chain gene rearrangements in the neoplastic cells. The results of the authors' studies indicate that "plasmacytoid T-cell lymphoma" associated with a chronic myeloproliferative disorder is of macrophage/monocyte lineage.

Antibody L26 recognizes an intracellular epitope on the B-cell-associated CD20 antigen

Monoclonal antibody L26 is a highly selective marker of B cells and B-cell neoplasms in paraffin-embedded tissues, but it suffers from the drawback that the target molecule has not been identified. In this paper we provide evidence by two independent techniques that antibody L26 recognizes an intracellular epitope on the CD20 antigen (a pan B-cell marker). When this antigen was redistributed on the surface of unfixed viable B cells by incubation with monoclonal anti-CD20 followed by anti-mouse Ig, the diffuse cytoplasmic staining of L26 was abolished and replaced by coincident dotlike labeling for antibody L26 and the CD20 antigen. None of the other antibodies tested (covering 10 different B-cell-associated antigens) had this effect on the L26 staining pattern. Furthermore, COS-1 cells transfected with cDNA encoding the CD20 molecule gave positive staining with antibody L26 and with two other CD20 reagents, but not with antibodies to other pan B-cell markers (eg, CD19 and CD22).

Preferential localisation of human lymphocytes bearing gamma delta T cell receptors to the red pulp of the spleen

About 4% of human T cells carry antigen receptor composed of gamma and delta chains (rather than alpha and beta chains). Double immunoenzymatic staining of frozen sections of 14 samples of human spleen showed that gamma delta bearing T cells were preferentially localised in the red pulp of this organ where on average they accounted for 17% of all T cells. There was no correlation between the number of gamma delta T cells and the diagnosis, with the exception of a case of malaria in which an unusually high number (40%) of T cells were of this type. The gamma delta bearing T cells were scattered randomly through the red pulp, and double staining combined with a marker of splenic sinusoids (CD36) showed that almost all lie outside the sinusoids within the cords of the red pulp. It is suggested that the double immunoenzymatic technique could be used for further studies of the prevalence of gamma delta bearing T cells in lymphocytic infiltrates.

Proliferation in non-Hodgkin's lymphoma: a comparison of Ki-67 staining on fine needle aspiration and cryostat sections

Assessment of the growth fraction of non-Hodgkin's lymphomas may provide useful additional prognostic information to that obtained with conventional histological criteria. The monoclonal antibody Ki-67 has been reported to provide such information immunocytochemically in tissue biopsy specimens from lymphoma as well as other tumours. This study was undertaken to assess whether this approach could be extended to fine needle aspiration (FNA) biopsy specimens which are becoming increasingly important in the diagnosis of lymphoma. In 21 cases of non-Hodgkin's lymphoma the rate of tumour proliferation estimated by Ki-67 immunostaining of FNA material, obtained from surgically removed specimens, was compared with that obtained on tissue biopsy. The correlation between both preparations was excellent, indicating that FNA biopsy material is suitable for the immunocytochemical assessment of the growth fraction of non-Hodgkin's lymphoma.

Immunophenotyping of acute leukemias using paraffin-embedded tissue sections

In a study of 55 patients with either acute lymphoid leukemia (ALL; 25 cases) or acute myeloid leukemia (AML; 30 cases), paraffin-embedded bone marrow particle sections were examined with a panel of monoclonal and polyclonal antibodies reactive toward lymphoid and myeloid-associated antigens, using the alkaline phosphatase-anti-alkaline phosphatase (APAAP) technique. All cases were previously classified according to the French-American-British (FAB) Co-operative Group, and cases of ALL were immunophenotyped by flow cytometry. Results indicated that myeloid-associated antibodies (Mac 387, KP 1 [CD68], antielastase, antilactoferrin, and antilysozyme) did not react with any case of ALL, M1-AML, or M6-AML, whereas at least one of these antibodies reacted with 20 of 21 (95%) cases of M2, M3, M4, and M5-AML. Anti-glycophorin C marked cases of M6-AML, whereas anti-CD3 labeled T-cell ALL. None of the antibodies tested specifically identified cases of B-cell ALL. The authors conclude that use of a selected panel of antibodies on paraffin-embedded bone marrow particle sections may be of value in the diagnosis and immunophenotypic classification of many cases of acute leukemias.

Lymphohistiocytic T-cell lymphoma (anaplastic large cell lymphoma CD30+/Ki-1 + with a high content of reactive histiocytes)

We describe 13 cases of a peculiar lymphoid tumour containing very large numbers of reactive histiocytes. The tumours occurred in young patients (mean age 14.8 y) who presented with systemic symptoms and superficial lymphadenopathy. Microscopic examination revealed a diffuse effacement of lymph node structure due to the presence of histiocytes intermingled with a variable number of anaplastic large lymphoid cells. The latter, in some cases, were isolated, while in others they were arranged in clusters or were diffusely present in residual sinuses. The large anaplastic cells expressed the activation markers CD30 (Ki-1), CD25 (interleukin-2 receptor), CD70 (Ki-24) and Ki-27, as well as varying combinations of T-associated molecules. The histiocytes expressed lysozyme and the CD11b (C3bi-R), CD11c (p150, 95) CD14, CD68 (KPI) and Ber-Mac3 antigens. Double staining with the antibody Ki-67 demonstrated that the proliferating components were the CD30-positive cells and not the histiocytes. T-cell receptor beta gene rearrangements were shown in three cases tested. The patients responded well to aggressive chemotherapy and nine are still alive, eight in complete remission. It is suggested that the tumour represents a well-defined clinico-pathological entity originating from activated T-lymphocytes.

Different isoforms of human FcRII distinguished by CDw32 antibodies

The Third and Fourth International Workshops on Leucocyte Differentiation Antigens identified six mAb, designated CDw32, reacting with human Ig FcR type II (FcRII). We have examined the immunohistochemical and immunocytologic reactivities of these antibodies and find that the antibodies could be divided into three classes of reactivity: 1) antibodies IV.3, CIKM3, and CIKM5 reacted with monocytes, macrophages and neutrophils; 2) antibodies KB61 and 41H.16 gave strong reactions with B lymphocytes, placental and hepatic endothelium, and weaker reactions with monocytes, macrophages, and neutrophils; 3) antibody 2E1 gave an intermediate reaction pattern. Immunoprecipitation from U937 cell lysates showed that antibodies KB61 and 41H.16 recognized Mr 41,000 and Mr 37,000 molecules whereas the other antibodies detected a Mr 42,000 molecule. Preclearing with antibody KB61 removed the Ag recognized by the other five antibodies confirming the identity of the Ag and demonstrating reactivity of KB61 with the Mr 42,000 molecule. Antibodies KB61 and 41H.16 precipitated a Mr 41,000 molecule from B lymphocytes. Flow cytometry and immunoprecipitation studies of cells transfected with cDNA clones coding for two isoforms of FcRII showed that all six of the antibodies react with both transfectants but the only immunoprecipitations were obtained using KB61 and 41H.16 and one of the transfectants. The protein sequence of KB61 Ag isolated from leukemic B cells showed close homology with the proteins encoded by the cDNA clones but diverged in the intracytoplasmic carboxyl-terminal region. It was concluded that preferential recognition of one or more of the numerous isoforms of FcRII underlies the differing reaction patterns of CDw32 antibodies.

Different isoforms of human FcRII distinguished by CDw32 antibodies

The Third and Fourth International Workshops on Leucocyte Differentiation Antigens identified six mAb, designated CDw32, reacting with human Ig FcR type II (FcRII). We have examined the immunohistochemical and immunocytologic reactivities of these antibodies and find that the antibodies could be divided into three classes of reactivity: 1) antibodies IV.3, CIKM3, and CIKM5 reacted with monocytes, macrophages and neutrophils; 2) antibodies KB61 and 41H.16 gave strong reactions with B lymphocytes, placental and hepatic endothelium, and weaker reactions with monocytes, macrophages, and neutrophils; 3) antibody 2E1 gave an intermediate reaction pattern. Immunoprecipitation from U937 cell lysates showed that antibodies KB61 and 41H.16 recognized Mr 41,000 and Mr 37,000 molecules whereas the other antibodies detected a Mr 42,000 molecule. Preclearing with antibody KB61 removed the Ag recognized by the other five antibodies confirming the identity of the Ag and demonstrating reactivity of KB61 with the Mr 42,000 molecule. Antibodies KB61 and 41H.16 precipitated a Mr 41,000 molecule from B lymphocytes. Flow cytometry and immunoprecipitation studies of cells transfected with cDNA clones coding for two isoforms of FcRII showed that all six of the antibodies react with both transfectants but the only immunoprecipitations were obtained using KB61 and 41H.16 and one of the transfectants. The protein sequence of KB61 Ag isolated from leukemic B cells showed close homology with the proteins encoded by the cDNA clones but diverged in the intracytoplasmic carboxyl-terminal region. It was concluded that preferential recognition of one or more of the numerous isoforms of FcRII underlies the differing reaction patterns of CDw32 antibodies.

CD30-positive large cell lymphomas ('Ki-1 lymphoma') are associated with a chromosomal translocation involving 5q35

A chromosomal translocation involving a breakpoint on the long arm of chromosome 5 at position q35 has been reported previously in 17 cases of neoplasia. In 14 of these cases the translocation involves exchange of material between chromosome 2 p23 and chromosome 5. Most cases had been diagnosed histologically as malignant histiocytosis but it was suggested recently, following the study of three cases in one of the author's laboratories, that such tumours are in reality lymphoid tumours. In the present paper we report on 12 further neoplasms with a translocation involving the 5q35 breakpoint and show that all were large cell lymphomas expressing the CD30 (Ki-1) antigen, often classifiable histologically as 'Ki-1 lymphoma'. In five cases there was evidence, based on antigen expression and/or genotypic studies, that the neoplasm was of T lymphoid derivation. These findings provide further evidence that translocations involving 5q35 are associated not with histiocytic malignancy, but with large cell lymphoid neoplasms, including typical cases of 'Ki-1 lymphoma' or 'anaplastic large cell lymphoma'. Since cell lines have been established from five of these cases it may be possible in the future to clone the breakpoint on chromosome 5 and to investigate whether there is a gene in its vicinity with oncogenic potential.

Peripheral T-cell lymphoma associated with hemophagocytic syndrome

Nine patients with an acute disease characterized by high fever, loss of weight, prominent hepatosplenomegaly, slight or no lymphadenopathy, abnormal liver function tests, and profound pancytopenia are reported. In all cases, the disease presented in the absence of any pre-existing disease or immunosuppressive therapy. In seven of the nine patients, survival was very short (mean = 7 weeks). Two patients are still alive: one had a relapse 24 months after the initial diagnosis, while the other is in complete remission. The main pathological feature was the infiltration of the marrow, spleen and liver by neoplastic T cells, accompanied by an exuberant hyperplasia of benign-looking, hemophagocytizing histiocytes. The term "peripheral T-cell lymphoma with hemophagocytic syndrome" is proposed for this condition. Retrospective analysis of stored paraffin material (1949 to 1965) from the Radcliffe Infirmary files suggests that at least some of the cases designated as "histiocytic medullary reticulosis" by Scott and Robb-Smith were examples of the syndrome herein described.

Malignant lymphomas of true histiocytic origin. A clinical, histological, immunophenotypic and genotypic study

The clinical, histological, immunophenotypic and genotypic properties of four cases of lymphoma of true histiocytic origin are described. The cases were identified by typing 925 non-Hodgkin's lymphomas by immunophenotypic and/or genotypic techniques, and they all presented with skin lesions. The histological and immunophenotypic examination showed dense, diffuse infiltrates of markedly pleomorphic mononuclear cells that were positive for macrophage-associated markers, and negative for B-cell, T-cell and myeloid cell-associated antigens. Staining for Ki-1 and epithelial membrane antigen was also negative. Gene rearrangements studies were performed in three cases, and all of these showed germline configuration of both T-cell receptor and immunoglobulin genes. In all cases, the clinical course was aggressive with rapid and widespread dissemination to internal organs, poor response to conventional chemotherapy, and short survival times (0.5 to 14 months). This suggests that although true histiocytic tumours are very rare, their recognition may be important for clinical and/or prognostic reasons.

Distribution of the CD68 macrophage/myeloid associated antigen

The distribution of the pan-macrophage CD68 antigen, recognized by six different monoclonal antibodies, was examined in human blood, tissue, and cell lines using APAAP staining and Western blotting. All antibodies stained monocytes and macrophages, but labelling of neutrophils, basophils, and lymphocytes was seen with some of the reagents. In addition, the CD68 antibodies demonstrated a variety of staining patterns on some non-haemopoietic cells. The subtle differences between the reactions of the different antibodies suggested that the CD68 antigen may be heterogeneous, possibly due to differences in glycosylation. While CD68 antibodies are very useful markers of the macrophage/myeloid series, the presence of small amounts of the antigen on some lymphoid and non-haemopoietic cells means that care should be taken when using them for the diagnosis of tumours of unknown origin.

Immunosuppression and thrombosis in renal transplantation: an immunohistological study

Renal biopsies were taken from 42 patients at seven and 21 days after renal transplantation. Paraffin sections from these specimens were examined immunocytochemically for the presence of platelet microthrombi in glomerular capillaries using the monoclonal antibody Y2/51. Patients were treated by one of four different immunosuppressive regimes, three of which included cyclosporin A, either alone or in combination with steroids and azathioprine. Microthrombi were detected in approximately 30% of biopsies and were much commoner in patients receiving multi-drug therapy. We conclude that, contrary to previous suggestions, glomerular capillary thromboses are not frequent in patients on cyclosporin A alone. They are found mainly in patients on multiple drug therapy, particularly when steroids are included. The detection of microthrombi is unlikely to be of assistance in the earlier detection of cyclosporin toxicity.

Immunocytochemical Analysis of Lymphoid Lesions Using -Fine Needle Aspiration Biopsy

Sixty-four cases of mainly lymphoid lesions were investigated by fine needle aspiration. Both conventional smears and cytospin preparations were made from this material. Diagnoses based on cytological and immunocytological criteria were made in 57 of these cases and include reactive hyperplasia, non-Hodgkin's and Hodgkin's lymphoma and metastatic carcinoma. Five cases were inadequate for diagnostic purposes and in 2 cases no definite diagnosis could be made. These diagnoses were confirmed using tissue sections in 48/51 cases (with only 3 cytological diagnoses significantly altered by histology) and supported by supplementary clinical information in 8 cases. These results demonstrate the value of FNA biopsy in the investigation of lymphoid lesions using both conventional cytology and immunocytochemistry.

The expression of the CD3 antigen in Hodgkin's disease

Tissue from 86 cases of Hodgkin's disease, fixed in formalin and embedded in paraffin, was immunostained for the T-cell marker CD3. Of these cases, 20 were selected on the basis of previous reactivity of Reed-Sternberg cells for T-cell associated antigens in frozen sections whilst the remaining 66 were retrieved from the routine pathology files. Five of the 20 selected cases and 22 of the retrieved cases showed predominantly cytoplasmic positivity in a subpopulation of Hodgkin and Reed-Sternberg cells. CD3 positive cells were present in all subtypes of Hodgkin's disease including three of nine lymphocyte predominance cases. It therefore appears that some Hodgkin and Reed-Sternberg cells can express the major T-cell antigen CD3. Although these findings are open to other interpretations, they are consistent with the hypothesis that at least some cases of Hodgkin's disease arise from activated T-cells.

Isolation and characterization of human fetal macrophages from placenta

Human fetal macrophages expressing class II major histocompatibility complex (MHC) antigens have been isolated from the stroma of the chorionic plate of term placentas, using enzymatic digestion procedures, and enriched by Percoll density centrifugation. These cells are adherent, phagocytic and express Fc receptors for IgG. By rosetting with bovine erythrocytes coated with IgG, they can be enriched to 77-95% purity. Placental macrophages isolated in this way stimulate the proliferation of lymphocytes from unrelated donors in mixed-cell cultures, and act as accessory cells in oxidative mitogenesis. In a family study, placental macrophages stimulated proliferation of maternal and paternal lymphocytes but there was no evidence for either priming to, or suppression by, the fetal cells when the responses of lymphocytes from the mother and her HLA identical twin were compared. The possibility that these cells can protect the fetus from infection and/or stimulate the production of maternal anti-fetal HLA-antibodies is discussed.

Diagnosis of myelomonocytic and macrophage neoplasms in routinely processed tissue biopsies with monoclonal antibody KP1

A new monoclonal antibody, KP1, against the CD68 antigen, which labels macrophages and other members of the mononuclear phagocyte lineage in routinely processed tissue sections, has been used to stain a range of lymphoid, histiocytic, and myelomonocytic proliferations. All 20 neoplasms of myeloid, myelomonocytic, and presumed macrophage derivation reacted with antibody KP1. None of the 22 cases of T cell neoplasia had positive reactions. Although 14 of 41 B lineage lymphomas and leukaemias were stained by antibody KP1, staining was usually confined to small dots of reactivity, in contrast to the strong and extensive cytoplasmic staining seen in the neoplasms of myeloid and macrophage/monocyte origin. Furthermore, positive B cell neoplasms were almost all small cell proliferations, which are unlikely to be confused with myelomonocytic malignancies. It was concluded that antibody KP1 is a valuable addition to a panel of monoclonal antibodies for phenotyping lymphomas, particularly in routinely fixed tissues. It should assist the pathologist in the recognition of extramedullary presentation of leukaemia, aid in the diagnosis of suspected cases of true histiocytic neoplasia, and allow for quantitation of macrophages infiltrating lymphomas and other solid tumors.

Detection of T cells in paraffin wax embedded tissue using antibodies against a peptide sequence from the CD3 antigen

Rabbit polyclonal antibodies were raised against a proline rich, peptide sequence, comprising 13 amino acids, in the cytoplasmic domain of the CD3 epsilon chain. Immunoprecipitation experiments showed that this antibody preparation recognised the CD3 antigen on human T lymphoblasts. The antibody stained normal T cells strongly in tissue sections which had been fixed in formalin or Bouin's solution and embedded in paraffin wax. Its reactivity with T cell lymphoma, when evaluated on a series of 96 previously phenotyped cases, closely agreed with the results obtained on cryostat sections. These results indicate that the specific detection of T cells in routinely processed tissue biopsy specimens is now technically feasible on a wide scale in diagnostic laboratories using CD3 peptide antibodies, and they also suggest that in future the use of anti-peptide antibodies may detect other lineage specific antigenic markers in paraffin wax sections.

Double immunocytochemical labeling of cell and tissue samples with monoclonal anti-bromodeoxyuridine

We describe a new monoclonal antibody (designated Bu20a) against bromodeoxyuridine (BrdU). This antibody was selected by screening against human tissues using the APAAP technique, and shows no crossreactivity with normal nuclei. It stains BrdU incorporated into the nuclei of a wide range of cell types, including human tonsil lymphoid cells, normal mouse tissues, and human tumors growing in nude mice. A double-labeling technique is described using this antibody in which cell smears or tissue sections are first labeled by an immunoperoxidase procedure for a cellular antigen (e.g., mouse or human histocompatibility class II antigen, T-lymphocyte antigen, keratin) and BrdU is then detected by indirect immunofluorescence. This procedure, which was applied to a variety of human and animal cells and tissues, is of wide potential value in analyzing the phenotype of S-phase cells and in co-localizing antigen expression and BrdU incorporation in tissue sections.

Molecule detected in formalin fixed tissue by antibodies MT1, DF-T1, and L60 (Leu-22) corresponds to CD43 antigen

Three monoclonal antibodies MT1, L60 (Leu-22), and DF-T1, were reported independently as recognising human T cells in routinely processed, paraffin wax embedded tissue. The present study was performed to compare these three reagents in terms of their immunocytochemical reactions and target molecule(s). On Western blotting of white cell extracts the three antibodies reacted with antigens of the same molecular weight (range 110-160 kilodaltons). Furthermore, their immunocytochemical reactivity with normal human cells, as analysed by two-colour flow cytometry, was essentially identical (labelling of monocytes, most T lymphocytes, and weak reactions with some B cells), and the antibodies gave closely similar reactions on 54 white cell derived neoplasms. To identify the target antigen for these three reagents, antibodies from the Third International Workshop on Leucocyte Antigens were reviewed and it was shown that the Western blotting and immunocytochemical reactions of MT1, L60 (Leu-22), and DF-T1 were identical with those of the reagents which defined the CD43 antigen (also known as leucosialin or sialophorin). Furthermore, all these antibodies reacted with cells transfected with a cDNA clone encoding CD43. It is concluded that antibodies MT1, L60 (Leu-22), and DF-T1 all recognise the heavily glycosylated myeloid/lymphoid associated CD43 antigen.

Expression of macrophage-associated antigens in tissues involved by Langerhans' cell histiocytosis (histiocytosis X)

The expression of macrophage antigens KP1, Mac, lysozyme, and alpha-1-antichymotrypsin was investigated on routine paraffin sections from 17 cases of Langerhans' cell histiocytosis (LCH). All the major clinical forms were represented, including single lesions and monosystemic and multisystemic disease. In all the cases, a variable fraction (3-35%) of LCH cells was immunoreactive with KP1 and anti-Mac; the staining pattern was quite typical because the immunoreaction product was often confined to the perinuclear space and the Golgi area. LCH cells containing lysozyme and AACT were detected less frequently; however, in positive cases the percentage of LCH cells immunoreactive for lysozyme and AACT was in the same range as that of KP1-positive cells. On immunostained cytosmears (one case), about 10% of the CD1a-positive cell population was reactive for the macrophage antigens CD14 and PAM-1. No association was noted between the number of KP1-positive cells and the clinical form and/or anatomic site of the lesion. Phagocytic macrophages were significantly and diffusely immunoreactive with KP1 and anti-Mac and for AACT and lysozyme. Multinucleated giant cells with irregular nuclei were frequently observed; these cells were rarely S-100 positive, were consistently stained by KP1 and AACT, and were occasionally anti-Mac positive. The authors' findings suggest that antimacrophage monoclonals, in conjunction with S-100 protein, may represent a useful tool to establish the diagnosis of LCH in paraffin-embedded material.