FMIP controls the adipocyte lineage commitment of C2C12 cells by downmodulation of C/EBP alpha.

Fms interacting protein (FMIP) is a substrate for Fms tyrosine kinase, and a nuclear/cytoplasm shuttling protein with a leucine zipper. As the phosphorylation of FMIP is observed in insulin-stimulated preadipocytes, we examined the role of FMIP in adipocyte differentiation, using the mesenchymal multipotent stem cells, C2C12 cells, that can differentiate into adipocytes, muscle cells and osteoblasts. Ectopic expression of FMIP in C2C12 impairs the adipocyte differentiation induced by treatment with insulin, dexamethasone and 3-isobutyl-1-methylxanthine. These cells exhibit muscle phenotype with multinuclear morphology. Furthermore, knockdown of endogenous FMIP expression by small interfering RNA improves adipocytic lineage commitment of C2C12 cells, while impairing muscle differentiation. Upon stimulation with insulin, CCAAT/enhancer binding protein (C/EBP)beta, but not C/EBPalpha, is upregulated in cells expressing ectopic FMIP, whereas in FMIP knockdown cells, C/EBPalpha is constitutively expressed. Ectopic expression of C/EBPalpha counteracts the effects of FMIP, whereas C/EBPalpha knockdown partially mimics the effects of FMIP in this system. Northern blot analysis and reverse transcriptase-polymerase chain reaction study reveal that ectopic FMIP-expressing cells do not contain the polyadenylated C/EBPalpha mRNA, but contain the C/EBPalpha pre-mRNA, suggesting that FMIP plays a role in RNA processing and/or export. Indeed, a member of the THO complex that plays a role in mRNA export, THOC1, is co-precipitated with FMIP. The data we have acquired on FMIP suggest that it is a target for tyrosine kinase receptors that potentiate mRNA export.

Role of the nucleophosmin (NPM) portion of the non-Hodgkin's lymphoma-associated NPM-anaplastic lymphoma kinase fusion protein in oncogenesis.

The NPM-ALK fusion gene, formed by the t(2;5)(p23;q35) translocation in non-Hodgkin's lymphoma, encodes a 75-kDa hybrid protein that contains the amino-terminal 117 amino acid residues of the nucleolar phosphoprotein nucleophosmin (NPM) joined to the entire cytoplasmic portion of the receptor tyrosine kinase ALK (anaplastic lymphoma kinase). Here, we demonstrate the transforming ability of NPM-ALK and show that oncogenesis by the chimeric protein requires the activation of its kinase function as a result of oligomerization mediated by the NPM segment. Sedimentation gradient experiments revealed that NPM-ALK forms in vivo multimeric complexes of approximately 200 kDa or greater that also contain normal NPM. Cell fractionation studies of the t(2;5) translocation-containing lymphoma cell line SUP-M2 showed NPM-ALK to be localized within both the cytoplasmic and nuclear compartments. Immunostaining performed with both polyclonal and monoclonal anti-ALK antibodies confirmed the dual location of the oncoprotein and also indicated that NPM-ALK is abundant within both the nucleoplasm and the nucleolus. An intact NPM segment is absolutely required for NPM-ALK-mediated oncogenesis, as indicated by our observation that three different NPM-ALK mutant proteins lacking nonoverlapping portions of the NPM segment were each unable to form complexes, lacked kinase activity in vivo, and failed to transform cells. However, NPM could be functionally replaced in the fusion protein with the portion of the unrelated translocated promoter region (TPR) protein that activates the TPR-MET fusion kinase by mediating dimerization through its leucine zipper motif. This engineered TPR-ALK hybrid protein, which transformed cells almost as efficiently as NPM-ALK, was localized solely within the cytoplasm of cells. These data indicate that the nuclear and nucleolar localization of NPM-ALK, which probably occur because of transport via the shuttling activity of NPM, is not required for oncogenesis. Further, the activation of the truncated ALK protein by a completely heterologous oligomerization domain suggests that the functionally important role of the NPM segment of NPM-ALK in transformation is restricted to the formation of kinase-active oligomers and does not involve the alteration of normal NPM functions.

A new variant anaplastic lymphoma kinase (ALK)-fusion protein (ATIC-ALK) in a case of ALK-positive anaplastic large cell lymphoma.

Anaplastic lymphoma kinase (ALK)-positive lymphomas ("ALKomas") constitute a distinct molecular and clinicopathological entity within the heterogeneous group of CD30-positive large cell lymphomas. In 80-85% of cases tumor cells express a Mr 80,000 hybrid protein comprising the nucleolar phosphoprotein nucleophosmin (NPM) and the ALK. We report here the cloning and expression of a novel ALK-fusion protein from an ALK-positive lymphoma. This case was selected for molecular investigation because of (a) the absence of NPM-ALK transcripts; (b) the atypical staining patterns for ALK (cytoplasm-restricted) and for NPM (nucleus-restricted); and (c) the presence of a Mr 96,000 ALK-protein differing in size from NPM-ALK. Nucleotide sequence analysis of ALK transcripts isolated by 5'-rapid amplification of cDNA ends revealed a chimeric mRNA corresponding to an ATIC-ALK in-frame fusion. ATIC is a bifunctional enzyme (5-aminoimidazole-4-carboxamide ribonucleotide transformylase and IMP cyclohydrolase enzymatic activities) that catalyzes the penultimate and final enzymatic activities of the purine nucleotide synthesis pathway. Expression of full-length ATIC-ALK cDNA in mouse fibroblasts revealed that the fusion protein (a) possesses constitutive tyrosine kinase activity; (b) forms stable complexes with the signaling proteins Grb2 and Shc; (c) induces tyrosine-phosphorylation of Shc; and (d) provokes oncogenic transformation. These findings point to fusion with ATIC as an alternative mechanism of ALK activation.

Systemic therapy with 3BIT, a triple combination cocktail of anti-CD19, -CD22, and -CD38-saporin immunotoxins, is curative of human B-cell lymphoma in severe combined immunodeficient mice.

We demonstrate in these preclinical studies that all severe combined immunodeficient mice injected with the human B-cell lymphoma cell line Ramos are cured when treated with a combination of anti-CD19, -CD22, and -CD38-saporin immunotoxins (ITs; termed 3BIT). Each component IT used individually did not cure the majority of animals but did significantly prolong their survival compared with PBS sham-treated controls, although the majority succumbed eventually to disease. The very significant improvement obtained with the three-IT combination 3BIT was not due to an antibody or antibody-plus-IT effect. We postulate that by targeting against these three cell surface molecules, we have effectively ensured delivery of saporin to each lymphoma cell with growth potential within the tumor, thus overcoming the problems of heterogeneity of target antigen expression that can limit the therapeutic efficacy of single-IT therapy or even two-IT combination therapy. These "proof of principle" findings have an obvious important bearing on antibody-based therapies for cancer and provide the rationale needed for the design and implementation of clinical trials with such combinations.

Nucleolar localization of the nucleophosmin-anaplastic lymphoma kinase is not required for malignant transformation.

The (2;5)(p23;q35) lymphoma-associated chromosomal translocation creates a novel fusion gene that incorporates parts of the anaplastic lymphoma kinase (ALK) receptor tyrosine kinase and nucleophosmin genes. We report here that the product of this fusion gene accumulates within the nucleoli of neoplastic cells, and that previous reports of a predominantly cytoplasmic localization for the protein represent a tissue-processing artifact. However, nucleolar accumulation of nucleophosmin-ALK may not be necessary for its oncogenic action, because an ALK protein expressed in a lymphoma carrying a variant (1;2) chromosomal translocation did not accumulate in nucleoli. Furthermore, an engineered hybrid TPR-ALK protein can transform rodent fibroblasts and produce lymphomas in mice while remaining confined to the cytoplasm. We propose that the transforming action of ALK may not be reliant on its nucleolar localization, a hypothesis that may have implications for studies of other proteins involved in oncogenesis that are relocalized after the creation of fusion genes.

Biochemical differences between SUDHL-1 and KARPAS 299 cells derived from t(2;5)-positive anaplastic large cell lymphoma are responsible for the different sensitivity to the antiproliferative effect of p27(Kip1).

An inverse correlation between p27(Kip1) expression and proliferation has been recently established in tissues derived from human lymphomas. The nucleophosmin-anaplastic lymphoma kinase (NPM-ALK)/phospholipase C-gamma (PLCgamma) complex also appears to play an important role in cell proliferation and malignant transformation of anaplastic large cell lymphoma (ALCL). In this study, we report that SUDHL-1 and KARPAS 299 ALCL-derived cell lines present different sensitivity to the antiproliferative effect of recombinant adenovirus-mediated p27(Kip1) expression or to serum-starvation in culture media. The results indicate that exogenous p27(Kip1) may interact with the NPM-ALK/PLCgamma pathway in SUDHL-1 but not in KARPAS 299 cells. This interaction correlates with changes in cell cycle and cell morphology observed mainly in SUDHL-1 cells. The percentage of SUDHL-1 cells in S phase declines, whereas it is almost unchanged in KARPAS 299 cells as compared to the controls after 96 h of infection with the recombinant adenovirus. Furthermore KARPAS 299 cells are resistant to serum-starvation due to deficient p27(Kip1)-upregulation and G1 arrest, whereas SUDHL-1 cells respond with increased G1 phase and p27(Kip1)-upregulation after 48 h of serum-starvation. Both cell lines express appropriate variation of levels of cyclins E and A, and Rb-phosphorylation as expected by growing them in culture media with different FBS content. Although both cell lines express cyclin D2, SUDHL-1 cells only present high level of cyclin D3. Moreover SUDHL-1 cells express high level of PTEN and the PKB/Akt pathway is constitutively activated in both cell lines. Lastly SUDHL-1 cells show higher levels of phosphotyrosine-containing proteins that is correlated with a higher NPM-ALK-associated autophosphorylation activity compared to KARPAS 299 cells. Our study clearly identifies some of the biochemical differences that may explain the difference in sensitivity to antiproliferative stimuli shown by two cell lines derived from the same type of lymphoma.

Primary and isolated anaplastic large cell lymphoma of the bone marrow.

Anaplastic large cell lymphoma (ALCL) is a T-cell lymphoma in which the majority of patients present with advanced stage III or IV disease. Here we report a case of ALCL where bone marrow was the only site of disease, in a 60-year-old man with pyrexia and pancytopenia. The diagnosis of ALCL was made on detection of CD30-positive anaplastic cells in the bone marrow, together with prominent hemophagocytosis. Genetics confirmed the clonal nature of the disease and showed it to be anaplastic lymphoma kinase (ALK) negative. Primary isolated bone marrow ALCL should be considered in the diagnosis of pancytopenia associated with hemophagocytosis.

Identification of the CD85 antigen as ILT2, an inhibitory MHC class I receptor of the immunoglobulin superfamily.

The CD85 molecule was originally defined at the Fifth Workshop on Leucocyte Antigens in 1993 by two monoclonal antibodies, VMP55 and GHI/75. This cell-surface glycoprotein is expressed on B cells, monocytes, and subpopulations of T and natural killer (NK) cells, and particularly high levels are expressed by normal and neoplastic plasma cells and by hairy cell leukemia B cells. We affinity purified the CD85 antigen and obtained tryptic peptide sequence which indicated that this molecule might be ILT2, a recently described inhibitory major histocompatibility complex class I receptor of the immunoglobulin superfamily. This was confirmed by showing that both of the original anti-CD85 mAbs stained ILT2 transfectants. The cell signaling role demonstrated for ILT2 is consistent with the previously reported involvement of CD85 in T cell activation.

Characterization of a new monoclonal anti-Fc gamma RII antibody, AT10, and its incorporation into a bispecific F(ab')2 derivative for recruitment of cytotoxic effectors.

Fc gamma RII (CDw32) on monocytes is capable of triggering both phagocytosis and lysis of chick red blood cells (CRBC) coated with antibody of the appropriate isotype. In this report we describe the production and characterization of a mouse monoclonal IgG1 antibody specific for Fc gamma RII and compare its activity in binding studies, tissue distribution and redirected cellular cytotoxicity (RCC), with the previously identified anti-Fc gamma RII antibodies KB61 and IV.3. Immunohistochemical and flow cytometry analyses demonstrated that AT10 binds very strongly to Fc gamma RII on normal monocytes, but only weakly to that expressed on lymphocytes. This pattern does not correspond to the staining seen with either KB61 or IV.3, and appears to give an intermediate profile. The binding constant (Ka) for the Fab' fragment of AT10 was calculated at 5.3 x 10(8) M-1, four times higher than that for KB61 (1.4 x 10(8) M-1). Bispecific F(ab')2 antibodies were constructed from Fab' fragments of AT10 or KB61 thioether-linked to Fab' from an anti-CRBC monoclonal antibody. These bispecific derivatives directed monocyte cytotoxicity against CRBC as efficiently as either a monoclonal or polyclonal anti-chick erythrocyte antibody. The bispecific F(ab')2 antibodies had a distinct advantage over the conventional reagents, in that they were not blocked in the presence of human Fc gamma at 3.5 mg/ml (a concentration comparable with that provided by IgG in serum). Therefore, bispecific derivatives constructed with the high affinity anti-Fc gamma RII antibody, AT10, may be used as therapeutic reagents for targeting tumour cell lysis in vivo.

The novel monoclonal antibody By114 helps detect the early emergence of a paroxysmal nocturnal hemoglobinuria clone in aplastic anemia.

The newly described monoclonal antibody By114 has been used with flow cytometry to investigate the status of the 90-kD glycosylphosphatidyl-inositol (GPI)-anchored component of CD66 (CD66c) on neutrophils from nine patients with paroxysmal nocturnal hemoglobinuria (PNH), seven with aplastic anemia/PNH, and 63 with aplastic anemia (AA) and a negative Ham's test. We have found that By114 is a sensitive indicator for recognizing patients with PNH and has helped delineate a group of nine patients with aplastic anemia and a negative Ham's test who have evidence of a larger PNH clone than indicated by other monoclonal antibodies (mAbs). By114 is a valuable marker for detecting the emergence of a PNH clone before the Ham's test becomes positive and is a more sensitive detector of deficient GPI-anchored proteins than other mAbs.

Anaplastic large cell lymphoma of maternal origin involving the placenta: case report and literature survey.

Non-Hodgkin's lymphoma (NHL) occasionally involves the placenta, and information of such occurrence should be useful for management of the mother and fetus. We report the first case of anaplastic large cell lymphoma (ALCL) disseminated to the placenta. The diagnosis was made via excisional biopsy of cervical lymphadenopathy in a 20-year-old woman at 27 weeks' gestation. Involvement of the placenta was noted on gross examination after cesarean section delivery of a girl at 30 weeks' gestation. The ALCL was microscopically confined to intervillous spaces in a manner similar to previous reports of other NHLs. The immunophenotype was characteristic (CD30+, EMA+, BNH9+), and the now frequently associated t(2;5)(p23;q35) translocation with this lymphoma was detected by the recently produced monoclonal antibody ALK1 against the nucleophosmin/anaplastic lymphoma kinase (NPM/ALK) chimeric protein. Complete remission was induced in the mother after delivery. Both mother and child are healthy at 10 years' follow-up. The case is reported in light of the sparse literature on lymphomatous involvement of the placenta.

Mantle zone lymphoma. Immuno- and enzymehistochemical studies on the cell of origin.

Using in-situ immuno- and enzymehistochemical techniques, the phenotype of the neoplastic cells in seven cases of mantle zone lymphoma (MZL) was compared to that in seven cases of nodular poorly-differentiated lymphocytic lymphoma (NPDLL). The neoplastic nodules in MZL consisted of medium-sized lymphoid cells with slightly irregular nuclei and finely dispersed chromatin, expressing monoclonal surface IgM or IgM plus IgD, and displaying membranous alkaline phosphatase (ALP) activity. These cells proliferated around follicular centers that demonstrated a polyclonal pattern of reactivity for both types of light chains and a distorted meshwork of dendritic reticulum cells. The neoplastic nodules in NPDLL consisted of small lymphoid cells with markedly irregular nuclei and coarsely granulated chromatin, expressing monoclonal surface IgM and lacking ALP-activity. These tumor cells also frequently expressed transferrin receptor and common acute lymphoblastic leukemia-antigen (CALLA). The neoplastic nodules showed an undistorted meshwork of dendritic reticulum cells, and were occasionally bordered by remnants of polyclonal lymphocytic coronas. These results confirm the previous suggestion that NPDLL arises from a cell type that is a normal constituent of follicular centers, whereas MZL arises from the lymphocytic corona. The morphological, enzyme- and immunohistochemical features of MZL cells strongly suggest that MZL arises from marginal zone lymphocytes, a subset of corona lymphocytes that expresses ALP-activity, high IgM and low IgD-levels.

Detection of t(2;5) in anaplastic large cell lymphoma: comparison of immunohistochemical studies, FISH, and RT-PCR in paraffin-embedded tissue.

Anaplastic large cell lymphoma (ALCL) is associated with the t(2;5)(p23;q35) translocation involving the anaplastic lymphoma kinase gene (ALK) and the nucleophosmin gene (NPM), which result in expression of a novel fusion protein, NPM-ALK (p80). Clinicopathologic studies have shown that ALK expression in ALCL is associated with improved 5-year survival rates when compared with ALCL lacking ALK expression. This study used paraffin-embedded tissue to compare interphase fluorescence in situ hybridization (FISH) and reverse transcriptase-polymerase chain reaction (RT-PCR) for the detection of t(2;5) with immunohistochemical analysis for the detection of ALK protein expression in 27 patients with CD30-positive ALCLs. ALK protein expression was detected with ALK1 antibody in 14 of the 27 patients. The neoplastic cells in 13 of these 14 lymphomas reacted with the p80NPM/ALK antibody. FISH, using a two-color ALK DNA probe, correlated 100% with the immunohistochemical results: a translocation involving the ALK gene was detected in all 14 lymphomas that reacted with anti-ALK1. RT-PCR, performed on 21 lymphomas, detected NPM-ALK mRNA in five of the lymphomas, all of which reacted with anti-ALK1 and showed ALK gene rearrangement by FISH. Lymphomas showing ALK1 reactivity occurred in a younger patient population (median age, 19.5 years) and were associated with improved 5-year survival rates (84%), as compared with lymphomas lacking ALK1 reactivity (median age, 68.0 years; 5-year survival rate, 35%; p = 0.008). We conclude that immunohistochemical studies, using antibody ALK1. and FISH for ALK gene rearrangement are equally effective for identifying patients with ALCL who have a favorable clinical outcome.

Statistical evaluation of diagnostic and prognostic features of CD30+ cutaneous lymphoproliferative disorders: a clinicopathologic study of 65 cases.

Several clinical and histopathologic features of 65 CD30+ cutaneous lymphoproliferations were evaluated for their diagnostic value between CD30+ primary versus secondary cutaneous lymphomas and for their prognostic significance. Primary cutaneous disease, spontaneous regression, and absence of extracutaneous spreading (but not age < or =60 years) were associated with a better prognosis. Epithelial membrane antigen, BNH9, CD15 or CBF.78 antigen were expressed in all types of cutaneous lymphoproliferations. However, epithelial membrane antigen immunoreactivity was more frequently expressed in CD30+ secondary cutaneous large-cell lymphoma. Among CD30+ primary cutaneous large-cell lymphoma, CD15 expression was only seen in localized skin lesions. P53 expression was not associated with spontaneous regression, extracutaneous spreading, or survival. Nested reverse transcriptase-polymerase chain reaction allowed the detection of NPM-ALK transcripts in 10 of 26 CD30+ primary and in 3 of 11 secondary cutaneous large-cell lymphomas. The ALK protein was detected in only 1 of 50 primary and in 4 of 15 secondary cutaneous CD30+ lymphoproliferations. In CD30+ primary cutaneous lymphoproliferation, NPM-ALK transcripts might be expressed by very rare normal or tumoral cells that are undetectable by immunohistochemistry. However, the expression of either NPM-ALK transcripts or ALK-protein was not correlated with prognosis or age in CD30+ cutaneous lymphoproliferations.

Immunoenzymatic labeling of monoclonal antibodies using immune complexes of alkaline phosphatase and monoclonal anti-alkaline phosphatase (APAAP complexes).

A murine monoclonal antibody specific for calf intestinal alkaline phosphatase has been prepared and used in an unlabeled antibody bridge technique for labeling monoclonal antibodies. This procedure--the alkaline phosphatase monoclonal anti-alkaline phosphatase (APAAP) method--gives excellent immunocytochemical labeling of tissue sections and cell smears, comparable in clarity and intensity to that achieved with immunoperoxidase labeling. If the enzyme label is developed with a naphthol salt as a coupling agent and Fast Red or hexazotized new fuchsin as a capture agent, a vivid red reaction product is obtained which is very easily detected by the human eye. For this reason the APAAP technique was found particularly suitable for labeling cell smears (for both cytoplasmic and surface-membrane antigens) and for detecting low numbers of antigen-bearing cells in a specimen (e.g., carcinoma cells in a malignant effusion). It was found possible to enhance the intensity of the APAAP labeling reaction substantially by repeating the second and third incubation steps (i.e., the unlabelled "bridge" antibody and APAAP complexes). The APAAP technique was superior to immunoperoxidase labeling for staining tissues rich in endogenous peroxidase, and could be used in conjunction with immunoperoxidase methods for double immunoenzymatic staining. The method was also applicable to the detection of antigenic molecules following their electrophoretic transfer from SDS-polyacrylamide gels to nitrocellulose sheets ("immunoblotting").

Human B cells cannot be triggered to kill target cells through their Fc gamma RII or Fc epsilon RII receptors.

There has been some controversy as to whether or not B cells can kill target cells through their Fc receptors. To address this, we have examined the ability of human B cells from a variety of sources to lyse hybridoma cells with specificity for either the B cell Fc gamma RII or Fc epsilon RII using a reverse killing assay, as well as their ability to lyse opsonized chicken erythrocytes using a classic ADCC assay. Tonsil B cells, chronic lymphocytic leukemia B cells, and Epstein-Barr virus-induced B cells, even after preactivation with a cocktail of cytokines, all failed to lyse any of these targets. We conclude that Fc gamma RII and Fc epsilon RII on human B cells are not cytotoxic trigger molecules.

Plasmacytoid monocytes (so-called plasmacytoid T cells) in granulomatous lymphadenitis.

Immunohistochemical evidence that the plasmacytoid T cell is closely related to the blood monocyte has been reported, and the term plasmacytoid monocyte has been proposed to describe this cell. The present study was undertaken to analyze the presence and distribution of plasmacytoid monocytes in human reactive lymph nodes showing epithelioid cell reactions. Numerous plasmacytoid monocytes (detected by a panel of monoclonal antibodies) were found in the majority of the lymph nodes studies, usually in close topographical association with epithelioid cells and multinucleated giant cells. The present findings suggest that plasmacytoid monocytes may give rise to epithelioid cells. This is further supported by the ultrastructural similarities between plasmacytoid monocytes and plasmacytoid epithelioid cells, a cell type that has been identified previously in granulomas and considered a direct precursor of the classical epithelioid cell.

SCL/Tal-1 expression in T-acute lymphoblastic leukemia: an immunohistochemical and genotypic study.

A comparative study of the immunohistochemical (Stem cell leukemia/T-cell acute leukemia [SCL/TAL-1] protein expression) and genotypic (deletions in the SCL/tal-1 gene) findings in T-acute lymphoblastic leukemia (T-ALL) is presented. Formalin-fixed tissue from 50 cases of T-ALL were stained with a novel monoclonal antibody, 2TL 242, which recognizes SCL/TAL-1 protein. Twenty-four cases showed nuclear immunolabeling of leukemic cells. Nuclear positivity was not evident in any other type of leukemia or lymphoma tested with the antibody. Genotypic analysis of 25 cases of T-ALL showed a deletion involving the SCL/tal-1 gene in nine cases. These results suggest that protein expression is not dependent on derangement of the SCL/tal-1 gene, because immunohistochemical detection of the protein was noted in the presence and absence of a tal-d1 deletion.

The differential diagnosis of routinely processed anaplastic tumors using monoclonal antibodies.

The value of immunohistological labeling with a panel of monoclonal antibodies in the diagnosis of routinely processed surgical biopsies has been assessed. The cases examined consisted of an unselected series of tumor biopsies referred during a 12-month period because of doubt as to the nature of the neoplasm and are representative of the type of diagnostic problem regularly encountered in routine surgical pathology. In 30 of the 38 cases studied, reactivity with monoclonal antileukocyte antibody (and nonreactivity with monoclonal antiepithelial antibodies) indicated that the tumor was a lymphoma. Seven of the remaining eight cases gave the reverse reaction pattern and therefore were classified as carcinomas, while one biopsy was unreactive with all antibodies. Review of the clinical details in each case showed that the clinical management in several instances was influenced by establishing the correct diagnosis and it therefore is suggested that immunohistologic examination should be used more widely in the study of tumors that give rise to diagnostic difficulty.

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.