Immunohistochemical analysis of monocytic leukemias: usefulness of CD14 and Kruppel-like factor 4, a novel monocyte marker

Detection of monocytic differentiation in myeloid neoplasms by immunohistochemical analysis is challenging owing to a lack of sensitive and/or specific antibodies. We tested the usefulness of immunohistochemical analysis for CD14, an antigen commonly detected by flow cytometry, and Krüppel-like factor 4 (KLF4), a potentially novel marker of monocytic differentiation, in a series of myeloid leukemias, including 53 acute myeloid leukemias with monocytic differentiation. These findings were compared with immunohistochemical findings for CD68 (KP-1), CD34, and CD163 and were also correlated with flow cytometric and enzyme cytochemical results. CD163 and CD14 are the most specific markers of monocytic differentiation, followed by KLF4. CD68, in contrast, is the most sensitive monocytic marker, and KLF4 is also significantly more sensitive than CD14 and CD163. These studies show that KLF4 is another marker of monocytic differentiation and that the combination of CD14 and CD163 can increase the diagnostic sensitivity for monocytic neoplasms.     

PG-M1: A New Monoclonal Antibody Directed against a Fixative-Resistant Epitope on the Macrophage-Restricted Form of the CD68 Molecule

A new anti-macrophage monoclonal antibody (PG-M1) was produced by immunizing BALB/c mice with fresh spleen cells from a patient with Gaucher's disease. PG-M1 reacts strongly with a fixative-resistant epitope of an intracytoplasmic molecule, selectively expressed by virtually all macrophages of the human body. Although attempts to immunoprecipitate the molecule recognized by PG-M1 have failed so far, the reactivity of the antibody with COS-1 and WOP cells transfected with a human complementary DNA clone encoding for the CD68 antigen suggests that PG-M1 is a new member of the CD68 cluster. However, unlike other CD68 antibodies (KP1, EBM11, etc.), which react with both macrophages and myeloid cells, PG-M1 detects a fixative-resistant epitope on the macrophage-restricted form of the CD68 antigen. In 957 routinely fixed, paraffin-embedded samples, PG-M1 showed a more restricted reactivity with elements of the monocyte/macrophage lineage than the previously described monoclonal antibodies MAC-387 (anti-calgranulins), KP1 (CD68) and Ki-M1P. Among hematological malignancies, PG-M1 only labels acute leukemias of M4 and M5 type and rare examples of malignant histiocytosis/true histiocytic sarcoma. In contrast, acute leukemias of the M1, M2, M3, M6, M7, and L1-L3 types, non-Hodgkin's lymphomas, and Hodgkin and Reed-Sternberg cells of Hodgkin's disease are consistently PG-M1-negative. In the daily diagnostic practice, PG-M1 seems to be particularly valuable for the diagnosis of myelomonocytic or monocytic leukemia and neoplasms of true histiocytic origin in routine paraffin sections.     

The value of immunohistochemistry for CD14, CD123, CD33, myeloperoxidase and CD68R in the diagnosis of acute and chronic myelomonocytic leukaemias

Rollins‐Raval M A & Roth C G
(2012) Histopathology  60, 933–942 The value of immunohistochemistry for CD14, CD123, CD33, myeloperoxidase and CD68R in the diagnosis of acute and chronic myelomonocytic leukaemias Aims: In the absence of adequate aspirate films and touch imprints, distinction of chronic myelomonocytic leukaemia (CMML) from acute myeloid leukaemia with monocytic differentiation (Mo‐AML) may be difficult solely on the basis of bone marrow biopsy morphological features. The aim of this study was to evaluate the diagnostic utility of a novel immunohistochemical panel for the diagnosis of acute and chronic myelomonocytic leukaemias in bone marrow biopsies. Methods and results: Immunohistochemical labelling for CD14, CD123, CD33, myeloperoxidase (MPO) and CD68R was assessed in 49 myeloid neoplasms with monocytic differentiation (24 CMMLs and 25 Mo‐AMLs) and compared with that of 15 non‐monocytic acute myeloid leukaemias (NM‐AMLs) and 17 non‐neoplastic controls. More than 20% CD14 immunohistochemistry (IHC)+ cells were seen only in Mo‐AMLs and CMMLs, although Mo‐AMLs showed wide variability and overlapped with other categories. More than 20% CD68R IHC+ cells had the highest sensitivity and specificity for Mo‐AML. Discrepant MPO–/CD33+ expression was specific for Mo‐AML but insensitive. A subset of blasts in Mo‐AMLs and NM‐AMLs were weakly CD123+. Conclusions: A significantly increased number of CD14+ cells raises the possibility of a myelomonocytic neoplasm but does not distinguish between CMML and Mo‐AML. Significantly increased numbers of CD68R IHC+ cells and a discrepant MPO–/CD33+ staining pattern are specific for Mo‐AML but are best utilized in a comprehensive panel.     

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.     

Monoclonal anti-T-cell antibodies react with circulating myeloid leukemia cells and normal tissue macrophages

Rabbit and monoclonal antibodies to human myeloid leukemia cells, monocytic leukemia cells and human thymocytes have shown the existence of common T-cell/myeloid/monocyte antigens. For this reason, the specificity of a series of monoclonal antibodies to human T-cells (OKT 1, 3, 4, 5, 6, 8, 9, 10; and NA1/34) was tested by immunofluorescence (cytofluorograph) and complement-mediated cytotoxicity against human myeloid leukemia and normal blood cells and leukemic cell lines. In addition, an immunohistological analysis of the specificity of OKT4, 9.3, Leu 3a, OKT3 and NA1/34 antibodies was performed using normal lymphoid tissues and a sensitive immunoperoxidase technique. Normal human peripheral blood mononuclear cells reacted with OKT3 ("pan T-cell", mean 54%), OKT4 ("helper T-cell", mean 35%) and OKT 5/8 ("suppressor T-cell", mean 18%) as previously reported. However, OKT3 reacted with the cell lines K562 (myeloid), RC2a and THP-1 (monocytoid) and U937 (macrophage) as well as with cells from 9/65 myeloid leukemia patients. OKT4 reacted with the cell lines HL60 (promyelocyte), RC2a and U937 and also with cells from 6/60 myeloid leukemia patients. OKT5 reacted with the cell lines K562 and THP-1. OKT1 ("pan T-cell") reacted with THP-1 and with myeloid and monocytic leukemia samples (5/32) as did OKT6 ("cortical thymocyte") (3/32). OKT10 ("common thymocyte") reacted with a range of leukemia cell lines (B-cell, pre- B-cell and macrophage) as well as 7/21 myeloid leukemia samples. In tissue sections Leu 3a, (9.3 and OKT4 to a lesser extent), stained paracortical lymphocytes, plus subcapsular and medullary macrophages, and dendritic cells present within the paracortex.(ABSTRACT TRUNCATED AT 250 WORDS)     

Leu-M1 immunoreactivity in nonhematopoietic neoplasms and myeloproliferative disorders. An immunoperoxidase study of paraffin sections

Leu-M1 is a differentiation antigen present on human myelomonocytic cells, which also has been identified in Reed-Sternberg cells and variants of Hodgkin's disease. This study further defines the tissue distribution of Leu-M1, with immunoreactivity observed for neoplastic cells in 14 of 28 formalin-fixed, paraffin-embedded nonhematopoietic neoplasms. With the use of monoclonal antibodies and an indirect immunoperoxidase technic, Leu-M1 was detected in adenocarcinomas of various sites (breast, lung, colon, thyroid, pancreas, and stomach), in squamous cell and transitional cell carcinomas, and in a small-cell anaplastic carcinoma. Evaluation of a wide variety of myeloproliferative disorders indicated that Leu-M1 effectively characterized mature and immature monocytic cells and myeloid cells at late stages of granulopoiesis, but it was not a reliable marker for early myeloid cells including blasts. Leu-M1 monoclonal antibodies are a useful diagnostic reagent, particularly in the assessment of lymphoproliferative disorders, but must be used with extreme caution and full awareness of its staining profile.     

Immunophenotypic profile of myeloid cells in granulocytic sarcoma by immunohistochemistry. Correlation with blast differentiation in bone marrow

The present study was designed to evaluate the lineage differentiation (particularly monocytic differentiation) of immature myeloid cells in granulocytic sarcoma (GS) by immunohistochemistry and correlate the results with lineage differentiation of blasts in the bone marrow and to determine the degree of maturation of the infiltrating myeloid cells in GS by immunohistochemistry using CD34 and HLA-DR. Immunohistochemical stains were performed on paraffin-embedded tissue from 17 GS lesions with lineage-associated markers: myeloperoxidase, CD68 (KP1), CD68 (PG-Ml), glycophorin A, factor VIII, and CD56; and with markers for blasts and immature myeloid cells: CD34 and HLA-DR. Our results show that positive staining with PG-M1, but not KP1, suggests monocytic differentiation of myeloid cells in GS and correlates with the monocytic differentiation of blasts in the bone marrow. Expression of CD56 is frequent in GS, especially when the marrow blasts have monocytic differentiation, and should not be interpreted as a primary natural-killer cell process. The immature myeloid cells in GS are frequently HLA-DR positive. However, CD34 positivity of the immature myeloid cells is relatively uncommon, except in cases with underlying myelodysplastic syndrome or chronic myelogenous leukemia.     

Comparative assessment of the recognition of domain-specific CD163 monoclonal antibodies in human monocytes explains wide discrepancy in reported levels of cellular surface CD163 expression

Background

CD163 is expressed exclusively on cells of the monocyte/macrophage lineage and is widely used as a marker of human macrophages. Further, it has been suggested as a diagnostic marker of monocyte/macrophage activity in inflammatory conditions and as a therapeutic target. However, studies continue to exhibit great discrepancy in the measured percentage of CD163-expressing blood monocytes in healthy individuals. In this study we sought to clarify this inconsistency in reported levels of CD163 surface expression by a detailed analysis of a panel of CD163 antibodies used in previous studies.

Materials and methods

The cellular distribution of CD163 on human peripheral blood monocytes in freshly drawn blood and peripheral blood mononuclear cells isolated from buffy-coats was investigated by flow cytometry using CD163 monoclonal antibodies recognizing scavenger receptor cysteine-rich (SRCR) domain 1 (MAC2-158), domain 4 (R-20), domain 7 (GHI/61), and domain 9 (RM3/1). The CD163 monoclonal antibodies were characterized in binding and endocytosis experiments in human macrophages and CD163-transfected Flp-In CHO cells. Calcium-dependent ligand binding was assessed using surface plasmon resonance, and the specificity of the CD163 monoclonal antibodies was analyzed by western blotting.

Results and discussion

Flow cytometric analysis revealed that the estimated proportion of CD163-expressing human peripheral blood monocytes increased when using CD163 monoclonal antibodies recognizing epitopes in the N-terminal part of CD163, remote from the membrane surface. Moreover, the proportion of CD163 positive monocytes observed was highly dependent on free calcium. GHI/61 did not exhibit CD163 binding in the presence of calcium as measured by surface plasmon resonance, which was in agreement with the concordant loss of binding in heparin-stabilized whole blood observed by flow cytometry. In contrast, RM3/1 exhibited weak binding to CD163 in the absence of calcium but high affinity binding to CD163 in the presence of calcium. R-20 and MAC2-158 were unaffected by extracellular calcium levels. The latter SRCR domain 1 mAb consistently recognized more than 80% CD163-positive monocytes in human peripheral blood.

Conclusion

Epitope accessibility and extracellular calcium dependence elucidate discrepancies in reported levels of monocytic CD163 expression. Utilizing monoclonal antibodies to the N-terminal part of CD163 more than 80% monocytes in human peripheral blood could be identified as CD163 positive, indicating that most, and conceivably all, human peripheral blood monocytes do express CD163.     

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.     

CD33 detection by immunohistochemistry in paraffin-embedded tissues: a new antibody shows excellent specificity and sensitivity for cells of myelomonocytic lineage

A new monoclonal antibody to CD33 that reacts in paraffin-embedded tissue samples was evaluated. The expected reactivity in granulocytic and monocytic cells was found in a tissue microarray composed of multiple tissue sites. There was no unexpected reactivity found in a wide variety of hematolymphoid and nonhematolymphoid disorders. In cases of acute leukemia, the CD33 antibody showed equivalent results by immunohistochemical analysis compared with flow cytometric analysis. The CD33 antibody was also found to be a useful marker in the workup of myeloid sarcomas. This anti-CD33 antibody will be a useful marker in the workup of acute leukemias and myeloid sarcomas on paraffin-embedded tissue samples.     

Functional expression of the CD163 scavenger receptor on acute myeloid leukemia cells of monocytic lineage

The hemoglobin-haptoglobin (Hb-Hp) scavenger receptor CD163 is a monocyte/macrophage-restricted surface antigen, whose expression is strongly up-regulated by glucocorticoids. We have previously shown that CD163 is expressed by acute myeloid leukemia (AML) cells of monocytic lineage. Herein, we expand this finding by demonstrating constitutive and glucocorticoid-enhanced CD163 expression on French-American-British M4/M5 AML cells, and leukemic blasts of other AML subtypes and normal hematopoietic progenitor cells do not express CD163. We provide evidence that the functional characteristics of CD163 are preserved on malignant cells by showing the capability of types M4/M5 blast cells to internalize Hb-Hp by a CD163-mediated mechanism. Together, our results identify CD163 as a potential target for therapeutic intervention. It is important that CD163 does not appear to be released from leukemic blasts under noninflammatory conditions, thus reducing the probability of off-target side-effects as a result of competitive binding of potential therapeutic ligands to nonmembrane-bound CD163.     

单核母细胞肉瘤的临床病理观察及免疫表型分析

目的探讨单核母细胞肉瘤的临床病理特征、诊断和鉴别诊断。方法从1990-2006年诊断的102例髓系肉瘤患者中筛选出5例单核母细胞肉瘤,进行临床病理回顾性研究和随访,以SP法检测其免疫表型。结果5例中男性3人,女性2人,2例为儿童,3例为成人。病程1周～12个月不等。4例有多处浅表淋巴结肿大;2例有多发性皮肤病变。免疫表型：5例瘤细胞均表达CD68（KP1）、CD68（PGM1）、溶菌酶和CD45;均不表达髓过氧化物酶、CD15、CD163、脱氧核苷酸转移酶、CD117以及T和B细胞分化抗原。Ki-67指数为40％～80％。5例患者均有随访,4例死亡,1例存活,平均生存时间6．25个月。结论单核母细胞肉瘤很少见,且预后差;在形态学上难以与粒细胞肉瘤和其他小细胞肿瘤相区别,须借助于免疫表型检测确诊。     

Morphologic and immunohistochemical evaluation of splenic hematopoietic proliferations in neoplastic and benign disorders.

Spleen is a common site of extramedullary hematopoiesis. Extramedullary hematopoiesis seen in non-neoplastic conditions can occasionally be extensive and raise concerns for a myeloid neoplasm. We compared the morphologic and immunohistochemical features of splenic hematopoietic proliferations seen in neoplastic myeloid disorders (eg chronic myeloproliferative disorders, myelodysplastic/myeloproliferative disorders and acute myeloid leukemias) to extramedullary hematopoiesis seen in a variety of reactive conditions. In all, 80 spleen specimens were reviewed. The presence of each marrow-derived lineage, dysplasia and immunohistochemical results were evaluated (CD34, CD117, myeloperoxidase, CD68, p53, TdT, CD42b and hemoglobin). Neoplastic hematopoietic proliferations in chronic myeloproliferative disorders are characterized by trilineage hematopoiesis with significant dysplasia in all cell lineages. Acute myeloid leukemia showed an increase in immature forms, which were highlighted by immunohistochemistry. Reactive extramedullary hematopoiesis showed variability in histologic features. Post-bone marrow transplant and thrombotic thrombocytopenic purpura/hemolytic-uremic syndrome spleens showed extramedullary hematopoiesis with some morphologic features of immaturity, which could simulate chronic myeloproliferative disorder. However, they lacked characteristic immunohistochemical features of neoplastic myeloid disorders such as positivity for CD34 or CD117.     

Histiocytic differentiation in acute monocytic leukemia

Myeloid histocytes of dendritic cells (DCs), Langerhans cells (LCs), and macrophages in varied tissues, as leukemic blasts in acute monoblastic and monocytic leukemia (AML-M_5a and M_5b), are derived from monocyte progenitors in bone marrow. Based on DC induction from hematopoietic stem cells, myeloid progenitors, and monocytes, and occasional expressions of histocyte-related antigens (HRAs) in M₅, we presume some M₅ cases share histiocytic phenotypes originally. To clarify the conception, 93 M₅ cases were tested with antibodies for HRAs, CD1a, CD163, S100, fascin, and langerin by immunostaining, and their morphologic characteristics were studied by light and transmission electron microscopy. The study revealed that 23 M₅ cases were positive for two or more kinds of HRAs and shared a serial of histocytic immunophenotype and morphologic features, which were closely associated with M_5b subtype and expression of CD14 in M₅.     

髓系肉瘤的临床病理特征及免疫组织化学在其鉴别诊断中的作用

目的探讨髓系肉瘤的临床病理特征、了解免疫组织化学检测在髓系肉瘤的诊断和鉴别诊断中的作用。方法对四川大学华西医院病理科1990年1月—2005年2月外检诊断的82例(102个样本)髓系肉瘤进行回顾性研究。收集相关临床资料并按 WHO(2001)关于淋巴造血组织肿瘤分类进行组织学分型,采用11种抗原标记的免疫组织化学检测(SP 法)并作生存分析。结果(1)本组病例的中位年龄为35.5岁,男女比为1.4:1。病变部位以淋巴结(43.1%)、皮肤(16.7%)、鼻(7.8%)、软组织(7.8%)和骨(6.9%)多见;以骨髓疾病相关性髓系肉瘤(51例,62.2%)多见,孤立性髓系肉瘤25例(30.5%);(2)82例中有79例(96.3%)为粒细胞肉瘤,其中母细胞型、幼稚型和分化型分别占51.9%、31.6%和16.5%;有3例(3.7%)为原始单核细胞肉瘤。51例(64.6%)粒细胞肉瘤之病变组织中可见数量不等的幼稚嗜酸性粒细胞,以幼稚型和分化型者多见,13例(31.7%)母细胞型粒细胞肉瘤中可见个别幼稚嗜酸性粒细胞;(3)95.9%(70/73)表达髓过氧化物酶(MPO),95.5%(63/66)表达溶菌酶,95.2%(60/63)表达 CD68_((KP1)),90.8%(59/65)表达白细胞共同抗原(LCA),85.7%(54/63)表达 CD43,77.8%(49/63)表达 CD117,58.7%(37/63)表达 CD99,54.0%(34/63)表达 CD15,22.2%(14/63)表达 CD34,4.7%(3/64)表达 CD68_((PG-M1))。Ki-67增殖指数为0.49±0.22;(4)本组资料的随访率为72.0%。患者的2年和5年生存率分别为36.1%和17.3%,未发现有意义的预后相关因素。结论髓系肉瘤可孤立出现或发生于各种骨髓增生性疾病的病程中或经治疗缓解后。病变组织中存在幼稚嗜酸性粒细胞,提示粒细胞肉瘤的诊断。免疫组织化学检测是诊断该肿瘤的重要手段。MPO 是粒细胞及其肿瘤的特异性标记,CD68_((PG-M1))是单核细胞及其肿瘤的特异性标记。全面了解患者的病史、血象和骨髓象等情况,可大大减少髓系肉瘤的漏诊和误诊。     

Ber-MAC3: new monoclonal antibody that defines human monocyte/macrophage differentiation antigen.

A new monoclonal antibody Ber-MAC3 is reported. It recognises a formol sensitive epitope of a not yet clustered monocyte/macrophage specific 140 kilodalton glycoprotein that is expressed on the cell surface and in the cytoplasm. In 30 cases of acute and chronic leukaemia, Ber-MAC3 staining was restricted to 15 myeloid leukaemias of M4 and M5 types. The tumour cells of two cases of true histiocytic malignancies were Ber-MAC3 positive, whereas those of all 280 malignancies of lymphocytic origin were negative. The latter included 52 cases of Hodgkin's disease and 41 cases of Ki-1 positive anaplastic large cell lymphomas which had previously been classified as true histiocytic lymphomas. Ber-MAC3 therefore seems to be of considerable value for selective identification of monocytes and macrophages at a certain stage of differentiation and seems to be suitable for diagnosing myelomonocytic or monocytic leukaemia and neoplasms of true histiocytic origin.     

The use of monoclonal antibody Y1/82A in the identification of acute myeloblastic and monocytic leukemias

A newly developed monoclonal antibody (Y1/82A), which binds a cytoplasmic antigen in peripheral blood monocytes and tissue macrophages, was tested for its ability to detect monocytic differentiation in acute myeloid leukemia, i.e., to distinguish French-American-British (FAB) groups M4 and M5 from FAB groups M1, M2, M3, M6 and M7. Staining was performed by the alkaline phosphatase-antialkaline phosphatase (APAAP) immunocytochemical technic on bone marrow smears from 29 cases of acute myeloid leukemia, on 17 normal peripheral blood and/or bone marrow smears, on bone marrows from 10 cases of lymphoid leukemia, and on lymph nodes of 13 patients with lymphoma. Neoplastic cells from 11 of 11 patients with either M4 or M5 leukemia had positive results, whereas only 2 out of 18 cases of M1, M2, M3, M6, and M7 leukemia had positive results. In normal samples, only peripheral blood monocytes, bone marrow macrophages, and megakaryocytes stained. Lymphoid neoplasms were unreactive. These results suggest that monoclonal antibody Y1/82A may be a useful reagent in detecting cases of M4 and M5 acute myeloid leukemia and that it offers a valuable alternative to nonspecific esterase cytochemistry.     

Human myeloid differentiation antigens identified by monoclonal antibodies to the myelomonocytic leukemia cell line RC-2A

Murine monoclonal antibodies to human myeloid cell surface differentiation antigens were prepared using the myelomonocytic leukemia cell line RC-2A as immunogen. Using a highly sensitive colorimetric assay, antibodies were selected as myeloid-associated based on their binding to RC-2A cells, but not to cells of the autologous EBV-transformed* B cell line Cess-B. Antibodies to five distinct cell surface antigens were extensively characterized for their binding to normal and leukemic hemopoietic cells, and to tissue sections. Three antibodies may identify antigens previously described in the International Leucocyte Typing Workshops (CD14, CD11b and CD31). The other two antigens appear to be expressed at low levels on the surface of RC-2A cells, and do not correspond to existing CD groups. One of these is also present on monocytes and neutrophils. Both were present on myeloid progenitor cells, as judged by depletion experiments with antibody and complement, although neither bound appreciably to myeloid leukemic cells as judged by indirect immunofluorescence. The other three antibodies bound preferentially to leukemic specimens displaying monocytic differentiation. Four of the antibodies could be demonstrated to bind to cells in frozen sections of tonsil and small intestine and all gave distinct patterns of reactivity. In particular, these antibodies differed markedly in their binding to endothelium, follicular dendritic cells and various types of tissue macrophages. These antibodies may be useful in the study of the differentiation of myeloid cells and in studies of immunologically mediated disease such as allograft rejection.     

Histologic and immunohistologic characterization of skin localization of myeloid disorders: a study of 173 cases

A retrospective analysis of 173 skin biopsy specimens of myeloid leukemia cutis (MLC) was performed to determine histologic and immunophenotypic criteria that could distinguish the varied myeloid disorders from one another. For the study, 11 relevant histologic items were scored and 12 antigens were studied (CD68 [KP1], CD163, CD14, CD4, myeloperoxidase [MPO], CD33, CD117, CD34, CD56, MIB-1, CD303, and CD123). Underlying myeloid disorders were essentially acute myeloid leukemias (65.3%), chronic myelomonocytic leukemias (11.0%), and refractory anemia (10.4%). Skin lesions were de novo in 7.5%, concurrent in 26.6%, and subsequent in 60.7%. Several morphologic characteristics (density, size of tumor cells, inflammatory background) were statistically useful in distinguishing between varied myeloid disorders. De novo MLCs displayed a specific morphologic profile. Association of CD68, CD33, and MPO could diagnose 100% of the cases of MLC. However, the immunohistochemical panel could not distinguish between the varied underlying myeloid disorders, with the exception that CD123 was particularly powerful in recognizing chronic myelomonocytic leukemia and also permitted reclassification of 4 cases as blastic plasmacytoid dendritic cell neoplasm.