Dual fluorochrome analysis of human B lymphocytes: phenotypic examination of resting, anti-immunoglobulin stimulated, and in vivo activated B cells

B cell-enriched preparations were prepared from human peripheral blood and lymphoid tissues by the depletion of T cells and monocytes. Only B cells by virtue of their staining with anti-B1 conjugated to fluorescein were additionally examined. Dual fluorescence staining and flow cytometric analysis demonstrated that the majority of "resting" human peripheral blood and splenic B cells co-express the B cell-restricted B1 and B2 antigens and lack B5, a B cell-restricted activation antigen, and interleukin 2 receptor (IL 2R). In contrast, nearly 2/3 and 1/3 of B1+ cells isolated from lymph node expressed IL 2R and B5 antigens, respectively. When B1+ B cells from peripheral blood and spleen were "activated" by anti-Ig, they lost the B2 antigen and acquired the B5 and/or IL 2R antigens. 2/3 of B1+ cells strongly expressed IL 2R, and up to 1/2 of B1+ cells co-expressed B5. Delineation of increased numbers of B1+ cells that co-express B5 and/or IL 2R within lymphoid tissues obtained from patients with diseases characterized by "activated" B cells provides in vivo confirmation that these phenotypic changes correlate with B cell activation. We believe that the identification and isolation of these and similar subsets of cells defined by differing cell surface phenotypes should further our understanding both of normal B cell activation and the pathophysiology of B cell disease states.     

Identification of effector cell protease receptor-1. A leukocyte-distributed receptor for the serine protease factor Xa

Mitogenesis, cell differentiation and immune-inflammatory responses are regulated by the coordinated assembly of proteases with specific cellular receptors. We have investigated the possibility that immune effector cells may express a high-affinity protease receptor. To address this hypothesis, we have generated mAb to factor V and its activated form Va, a circulating plasma protein that binds the serine protease of the coagulation cascade, factor Xa. Further, by flow microfluorimetry screening, we have isolated a panel of these mAb that recognize a surface molecule expressed on transformed monocytic cells. We now show that these mAb bind to blood monocytes, to CD3- CD16+ CD56+ NK cells, and with considerable heterogeneity, to neutrophils. A small subset of CD3+ cells (5 to 10%) was also identified by these probes and further phenotypically characterized by two-color flow microfluorimetry as predominantly coexpressing CD2, CD4 or CD8, CD57, CD11b, and alpha/beta TCR. This subset of CD3+ cells was expanded in vitro by both lectin- or Ag-specific stimulation. In addition, long term alloreactive stimulation resulted in approximately 8- to 10-fold increased expression of the molecule recognized by these mAb. Functional analyses were performed on a selected T cell clonal derivative of the transformed cell line HuT 78. These cells bound 125I-factor Xa in a specific reaction saturated at 194,000 +/- 26,000 molecules/cell with a Kd approximately 10 to 20 nM and inhibited by the mAb panel described above. These data suggest that immune effector cells express a dynamically regulated protease receptor that is immunologically related to the plasma coagulation protein factor V and its activated form Va. We propose the term effector cell protease receptor-1 to tentatively identify this molecule, and we speculate on its possible involvement in specialized protease-mediated effector functions.     

4F2 monoclonal antibody recognizes a surface antigen on spread human fibroblasts of embryonic but not of adult origin

The 4F2 monoclonal antibody (mAb) has been shown to recognize a 120- kilodalton glycoprotein expressed on the cell surface of human peripheral blood monocytes, activated (but not resting) T or B cells, and T and B lymphoblastoid cell lines. In this report we show that 4F2 mAb specifically binds to the surface of adherent human embryonic fibroblasts but fails to bind to normal adult fibroblasts. Moreover, 4F2 antigen was expressed on sarcoma-derived or SV40-transformed adult fibroblastic cells. Finally, addition of 4F2 mAb inhibited the growth of cultured HT-1080 fibrosarcoma cell line, but had no inhibitory effect on various embryonic and adult normal or transformed fibroblasts.     

Enhancement of human neutrophil functions by a monoclonal antibody directed against a 19-kDa antigen.

A mouse IgG mAb termed P1C3 was raised against A23187-treated human peripheral blood neutrophils and has been shown to recognize an Ag with an apparent molecular mass of 19 kDa, herein named p19. This p19 Ag was weakly expressed at the cell surface of resting human peripheral blood neutrophils and monocytes, but its cell surface expression was dramatically increased upon activation of these cell types with different secretagogues, including FMLP, PMA, and the calcium ionophores A23187 and ionomycin. A large latent pool of p19 molecules became accessible by immunofluorescence flow cytometry after cell permeabilization of resting neutrophils. A practically total translocation of the intracellular pool of this p19 molecule to the plasma membrane was achieved under appropriate cell stimulation, which induced an almost total degranulation of neutrophil secretory granules. The p19 Ag was absent from platelets, PBL, as well as from the human promyelocytic cell line HL-60, the human promonocytic cell line U937, and the human lymphoid cell lines Daudi and Jurkat. The p19 Ag was also expressed by circulating and/or interstitial neutrophils and monocytes in distinct tissues examined. The mAb P1C3 was found to enhance several neutrophil responses, such as chemotaxis, cell adhesion, phagocytosis, and respiratory burst. These data indicate that the mAb P1C3 recognizes an intracellular Ag in human resting mature neutrophils and monocytes, which upon cell activation is translocated to the cell surface and is able to affect cell functionality.     

Biochemical basis of HLA-DR and CR3 modulation on human peripheral blood monocytes by lipopolysaccharide

The biochemical events leading to enhanced membrane expression of HLA-DR and CR3 by human peripheral blood monocytes (MO) following exposure to bacterial lipopolysaccharide (LPS) were examined. In a previous study we demonstrated that an increase in intracellular calcium was necessary, but not sufficient, for MO to increase membrane expression of both antigens within 1 hr of addition of LPS. The present study was initiated to examine the other biochemical requirements which lead to the MO response to LPS. Enhanced expression of both antigens following addition of LPS was dependent on microfilament function, but independent of microtubule function and of protein synthesis. Inhibition of formation of cyclooxygenase or lipoxygenase metabolites of arachidonic acid had no effect on HLA-DR or CR3 modulation by LPS. A role for phosphatidylinositol metabolism was suggested by the inhibition of the MO response to LPS by dibutyryl cAMP and theophylline and by the enhanced expression of both antigens following addition of phorbol diesters. However, H-7, a putative inhibitor of protein kinase C, did not alter the MO response to LPS or phorbol diesters. These results suggest that LPS enhances expression of HLA-DR and CR3 by inducing redistribution of these antigens from an intracellular pool. The data also support a role for the generation of hydrolysis products of phosphatidylinositol, leading to calcium redistribution and activation of protein kinase C or other kinases, in the MO response to LPS.     

Molecules involved in the adhesion and cytotoxicity of activated monocytes on endothelial cells.

Our study was designed to investigate the surface molecules involved in the adhesion and cytotoxicity of activated human monocytes on resting and IL-1-stimulated endothelial cells (EC). Monocytes, exposed to the prototypic activating stimuli IFN-gamma and LPS, showed increased binding to resting and IL-1-treated EC. Activated monocytes were cytotoxic for resting and IL-1-treated EC in a 24- to 48-h [3H]TdR release assay. Anti-CD18 mAb significantly inhibited binding of monocytes on EC: in particular they caused 59 and 22% inhibition of adhesion of activated monocytes to resting and IL-1-stimulated EC, respectively. Anti-VLA4 mAb had little or no effect on binding when used alone, but combined use with anti-CD18 revealed an important role for this adhesion pathway: in particular, VLA4-dependent adhesion accounted for 40% of the binding of activated monocytes on IL-1-treated EC. Anti-CD18 mAb caused similar inhibition (77 and 81%) of the cytotoxicity of activated monocytes on resting and IL-1-treated EC in spite of the fact that this pathway accounted for only 22% of binding to activated EC. Moreover, anti-VLA4 mAb, alone or in combination with anti-CD18, had no effect on cytotoxicity. These results suggest that adhesion of activated monocytes to activated EC involves the CD18- and VLA4-dependent pathways, but that the former is dominant for the expression of cytotoxicity. Thus, in the ensemble of adhesion molecules available for interaction between endothelium and activated monocytes, the hierarchy of their importance may vary for different functions.     

Chemokine-like receptor 1 expression and chemerin-directed chemotaxis distinguish plasmacytoid from myeloid dendritic cells in human blood

Plasmacytoid dendritic cells (pDCs) are versatile cells of the immune response, secreting type I IFNs and differentiating into potent immunogenic or tolerogenic APCs. pDCs can express adhesion and chemokine receptors for lymphoid tissues, but are also recruited by unknown mechanisms during tissue inflammation. We use a novel mAb specific for serpentine chemokine-like receptor 1 (CMKLR1) to evaluate its expression by circulating leukocytes in humans. We show that CMKLR1 is expressed by circulating pDCs in human blood, whereas myeloid DCs (mDCs) as well as lymphocytes, monocytes, neutrophils, and eosinophils are negative. We identify a major serum agonist activity for CMKLR1 as chemerin, a proteolytically activated attractant and the sole known ligand for CMKLR1, and we show that chemerin is activated during blood coagulation and attracts pDC but not mDC in ex vivo chemotaxis assays. We conclude that CMKLR1 expression and chemerin-mediated chemotaxis distinguish circulating pDCs from mDCs, providing a potential mechanism for their differential contribution to or regulation of immune responses at sites of bleeding or inflammatory protease activity.     

Monoclonal antibodies against human myelomonocytic cells: detection of certain lineage-specific antigens on CFU-GM progenitor cells

A series of monoclonal antibodies (mAb) were raised against nonlymphoid leukemic cell lines. Three of them have been characterized in detail. mAb H8 (IgG2), mAB U2 (IgG1), and mAb ML143 (IgM) were established with HEL, an erythroleukemia cell line, U937, a monocytoid (histiocytic) line, and ML-1, a myeloid cell line as immunogen, respectively. A 65 to 75 KD polypeptide was precipitated from monocytes by mAb H8, a 160 KD protein from monocytes by mAb U2, and two broad bands in the regions of 150 and 195 KD from granulocytes by mAb ML143. All three mAb stained peripheral blood monocytes and granulocytes, but not lymphocytes, platelets, and erythrocytes. The mAb reacted with immature myeloid cells in bone marrow, ranging from myeloblasts to mature myelomonocytic cells. They also were reactive with various nonlymphoid cell lines and leukemia of myelomonocytic origin. They did not react with B cell lines and B cell CLL cells. By complement-mediated cytolysis and/or an immune rosette method, antigens H8 and U2 were found to be expressed on the vast majority of CFU-GM (14 days) progenitors but not on BFU-E. Antigen ML143 was not expressed by either progenitor. Furthermore, ML143 antigen was found on T leukemia cell lines, a subpopulation of mitogen-activated T cells, and certain non-T/non-B ALL cells. This reactivity was not found with mAb H8 and U2. The relationship between these mAb and those reported are discussed. The possibility of using these mAb to obtain a markedly enriched CFU-GM progenitor population is also raised.     

A monoclonal antibody detects macrophage maturation antigen which appears independently of class II antigen expression. Reactivity of monoclonal EBM11 with bovine macrophages

A mAb EBM11, raised against human macrophages [M phi] was found to detect a bovine M phi diameter-subpopulation. The Ag was strictly intracellular and was expressed in M phi only at a certain state of maturation. Its expression was regulated independently of the activation state of the cells, as revealed by treating M phi in vitro with bovine rIFN-alpha I1, IFN-gamma, or TNF-alpha, all potent M luminal diameter activators. Such treatment had no apparent effect on Ag expression. The Ag was present in 1 to 5% of peripheral blood leukocytes, i.e., up to 20% of circulating blood monocytes, in both normal noninfected cattle and in cattle persistently infected with bovine viral diarrhoea virus. Blood monocytes of the latter group were activated in vivo, but apparently did not reach a more mature state than found in noninfected animals. After an acute infection with bovine herpes virus type 1, the frequency and total number of EBM11+ cells decreased dramatically in inverse relationship to an equally significant increase in frequency and total number of circulating monocytes. In cryostat sections of normal tissues, the EBM11 mAb reacted with sinus M phi and M phi in germinal centers of lymphoid tissues, with alveolar M phi and liver Kupffer cells. In skin it reacted with few scattered M phi in the dermis, but not with epidermal Langerhans cells. This latter feature distinguishes the bovine system from the human. In virus-induced inflammatory processes in skin and keratinized epithelia EBM11+ cells constituted a subpopulation of the infiltrating M phi. The data obtained suggest that EBM11 mAb could be useful both for the elucidation of differentiation/maturation pathways of cells of the monocyte-macrophage lineage as well as for studies of M phi-virus interactions in virus infections. In either aspect cattle could provide a useful comparative model.     

Identification and characterization of a hamster monoclonal antibody anti-2.28 directed against a 70-kilodalton activation antigen on human monocytes

Hamster mAb against activated human monocytes were examined for their reactivities against monocyte activation Ag. One mAb, anti-2.28, stained only monocytes activated with LPS plus IFN-gamma, but not unactivated peripheral blood monocytes, polymorphonuclear leukocytes, lymphocytes, RBC, and platelets. However, it stained peripheral blood T cells activated with PMA plus anti-CD3 and peripheral blood and tonsillar B cells activated with PMA plus anti-mu. Of the 35 cell lines of diverse origin examined for immunofluorescence staining by anti-2.28, only EBV-transformed cell lines showed strong staining by this mAb. One pre-B cell line, Nalm-12, could be induced by PMA to exhibit intermediate staining. Immunoprecipitation studies identified the 2.28 Ag as a 70- to 85-kDa monomer. Immunofluorescence staining, immunoprecipitation, and peptide mapping studies indicated that 2.28 was different from a number of monocyte and lymphocyte surface Ag including Mo3e, B-4 (CD19), B-5, CD39, and the G28-8 Ag Bgp 95. These studies suggest that 2.28 may be a novel hemopoietic non-lineage-specific activation Ag.     

Implication of HLA class I molecule from monocyte in T-cell activation by CD2 or CD3 monoclonal antibodies

The role of monocytes in human T-cell activation by monoclonal antibodies (mAb) recognizing CD3 molecule or by 2 mAb pairs directed against different epitopes of CD2 "GT2+T11(1)" or "D66+T11(1)" has been studied. It appears that HLA-cl I molecules from monocytes are involved in the early activation phase of T-cells stimulated by CD3 or CD2 when direct contacts between T-cells and monocytes are required. Thus, pretreatment of monocytes with HLA-cl I mAb inhibited IL 2 receptor appearance and IL 2 synthesis on T-cells stimulated by CD3 mAb or CD2 "GT2+T11(1)" mAb pair.     

Functional effects of a monoclonal antibody directed against a distinct epitope on 4F2 molecular complex in human peripheral blood mononuclear cell activation.

The 4F2 antigenic complex is expressed on most human cell lines in culture, on monocytes and activated lymphocytes, but not on resting T and B lymphocytes. Monoclonal antibody (mAb) CB43 recognizes an epitope of the 4F2 heterodimer either located on the light chain or dependent on the conformation of the molecule. The binding of CB43 mAb to peripheral blood mononuclear cells (PBMC) induced a dose-dependent comitogenic effect in the presence of submitogenic concentrations of anti-CD3 mAb. Significant amounts of interleukin (IL)-1 beta but not IL-2 or interferon-gamma were released in the supernatant. Pretreatment of monocytes with CB43 mAb increased the phytohemagglutinin-induced T lymphocyte proliferation. However, CB43 mAb did not exert agonistic effects on activated T lymphocytes. Depletion of CB43+ cells from PBMC decreased the proliferation and generation of cytotoxic effector cells induced by a mannoprotein (MP) derived from Candida albicans cell wall but not by recombinant IL-2. Furthermore, depletion of CB43+ cells from PBMC preactivated with MP or rIL-2 led to a significant decrease in their cytotoxic activity. CB43 mAb did not inhibit the growth of cell lines nor the proliferation of T cells. Thus CB43 mAb identifies a distinct functional epitope on the 4F2 molecular complex and might be useful in further studying the role of this molecule in cellular activation.     

A DC-specific cytolytic T lymphocyte line is OKT8+1

A human cytotoxic T lymphocyte (CTL) line, A9, was generated by limiting dilution and was selected because of its apparent DC specificity. A9 is 100% OKT3+, 90% OKT4+, and 10% OKT8+, but by negative selection the CTL present are entirely OKT8+. These OKT8+ CTL are totally inhibitable by Genox 3.53, an anti-DC1 monoclonal antibody (mAb), and Leu-10, an anti-DC subgroup mAb, but are not inhibitable by a panel of anti-HLA-DR mAb. These CTL are also inhibitable by anti-OKT3 and anti-LFA-2 but not by OKT4 or OKT8 mAb. These findings extend previous studies that showed that OKT8+ CTL recognize HLA-A,B antigens, whereas OKT4+ CTL recognize HLA-DR and SB antigens. It is possible that an as yet undefined T cell surface molecule is involved in DC recognition.     

High-dose leptin activates human leukocytes via receptor expression on monocytes

Leptin is capable of modulating the immune response. Proinflammatory cytokines induce leptin production, and we now demonstrate that leptin can directly activate the inflammatory response. RNA expression for the leptin receptor (Ob-R) was detectable in human PBMCs. Ob-R expression was examined at the protein level by whole blood flow cytometry using an anti-human Ob-R mAb 9F8. The percentage of cells expressing leptin receptor was 25 +/- 5% for monocytes, 12 +/- 4% for neutrophils, and 5 +/- 1% for lymphocytes (only B lymphocytes). Incubation of resting PBMCs with leptin induced rapid expression of TNF-alpha and IL-6 mRNA and a dose-dependent production of TNF-alpha and IL-6 by monocytes. Incubation of resting PBMCs with high-dose leptin (250 ng/ml, 3-5 days) induced proliferation of resting cultured PBMCs and their secretion of TNF-alpha (5-fold), IL-6 (19-fold), and IFN-gamma (2.5-fold), but had no effect on IL-4 secretion. The effect of leptin was distinct from, and additive to, that seen after exposure to endotoxin or activation by the mixed lymphocyte reaction. In conclusion, Ob-R is expressed on human circulating leukocytes, predominantly on monocytes. At high doses, leptin induces proinflammatory cytokine production by resting human PBMCs and augments the release of these cytokines from activated PBMCs in a pattern compatible with the induction of Th1 cytokines. These results demonstrate that leptin has a direct effect on the generation of an inflammatory response. This is of relevance when considering leptin therapy and may partly explain the relationship among leptin, proinflammatory cytokines, insulin resistance, and obesity.     

Antigens associated with the activation of murine mononuclear phagocytes in vivo: differential expression of lymphocyte function-associated antigen in the several stages of development

Two well-characterized antigens [Mac-1 and lymphocyte-function-associated antigen (LFA-1)], expressed on a variety of leukocytes, are members of a family of surface proteins associated with multiple recognition functions. To analyze expression of these proteins during macrophage development, we utilized both radioimmunoassay and flow cytometry. As previously reported, Mac-1 is expressed on murine macrophages in all stages of development. We found LFA-1 to be present on murine mononuclear phagocytes but only in certain stages of their development. Specifically, we found LFA-1 was expressed on murine tissue macrophages but only on those activated in vivo by bacillus Calmette Guerin (BCG) or, to a lesser extent, primed by pyran copolymer. Although LFA-1 was absent on inflammatory (responsive) and resident tissue macrophages it was also present on blood-borne monocytes. Activated macrophages also selectively expressed the H-11 and Ly-6 antigens. Thus, these data indicate that LFA-1 is selectively expressed on mononuclear phagocytes of the tissues but only on those in the primed and activated stages of development.     

Characterization of mononuclear phagocyte subpopulations in the human lung by using monoclonal antibodies: changes in alveolar macrophage phenotype associated with pulmonary sarcoidosis

Current concepts of pulmonary sarcoidosis suggest that the alveolar macrophage plays a central role in the pathogenesis of the disease. To help define the population of alveolar macrophages in sarcoidosis, we compared the surface phenotype of alveolar macrophages from patients with sarcoidosis and from normal individuals by using monoclonal antibodies (63D3, OKM1, M phi P-9, M phi S-1, 61D3, and M phi S-39) that detect surface antigens on cells of monocyte/macrophage lineage. Although almost all blood monocytes expressed surface antigens detected by each of these antibodies, only a minority of normal alveolar macrophages expressed the same surface antigens (p less than 0.05, each comparison). However, in sarcoidosis, the percentage of alveolar macrophages expressing these surface antigens was increased (p less than 0.05, each comparison with normal alveolar macrophages). Several findings supported the conclusion that the increased expression of these monocyte-lineage surface antigens on sarcoid alveolar macrophages resulted from increased recruitment of monocytes to the lung in sarcoidosis and not from abnormal "activation" of alveolar macrophages. First, alveolar macrophages expressing these antigens had an immature morphology. Second, in vitro cultivation of blood monocytes and alveolar macrophages in the presence of immune and inflammatory mediators, including mediators known to be present in the lung in sarcoidosis, did not prevent the loss of expression of monocyte-lineage surface antigens from monocytes or induce reexpression of monocyte-lineage surface antigens on alveolar macrophages. Third, the expression of monocyte-lineage surface antigens was only increased on sarcoid macrophages from patients whose lower respiratory tract contained an increased number of T lymphocytes, cells known to release monocyte chemotactic factor in sarcoidosis. Consistent with the knowledge that corticosteroids usually suppress the alveolitis of active sarcoidosis, when the expression of alveolar macrophage surface antigens was evaluated before and during therapy, the percentage of alveolar macrophages expressing monocyte-lineage surface antigens returned to normal after 1 to 3 mo of therapy.(ABSTRACT TRUNCATED AT 400 WORDS)     

14-3-3 zeta protein secreted by tumor associated monocytes/macrophages from ascites of epithelial ovarian cancer patients

Tumor associated monocytes/macrophages (MO/MA) are known contributors to the immune-inflammatory cell environment of advanced epithelial ovarian carcinoma (EOC). The secreted proteome of ascitic MO/MA was examined as an aid to the discovery of novel proteins in EOC that are likely to have biological relevance in the inflammatory pathways of EOC. Ascitic fluid MO/MA were isolated from EOC patients, grown short-term in serum-free media. MO/MA supernatants were analyzed for secreted proteins by HPLC fractionation followed by LC-tandem mass spectrometric analysis. The 14-3-3 zeta adaptor protein was identified in supernatants of three of three EOC patients but not in supernatants of buffy coat monocytes isolated from normal donors or the established monocyte cell line THP1. Moreover, 14-3-3 zeta was identified in ascitic fluids in eight of eight chemotherapy-naïve patients by both immunoblot and mass spectrometric analysis. Immunofluorescent staining for 14-3-3 zeta demonstrated expression of the protein on ascitic and peritumoral macrophages in EOC patients. 14-3-3 zeta was also expressed on endothelial cells in the peritumoral stroma and partially on tumor cells. Uptake of 14-3-3 zeta was observed in EOC cell lines co-cultured with the recombinant protein expressed in E. coli. It is demonstrated for the first time that the important adaptor protein 14-3-3 zeta is common to the secretome of ascitic MO/MA and the ascites of advanced EOC patients.     

CD14 contributes to the adherence of human monocytes to cytokine-stimulated endothelial cells.

Monocyte adherence to endothelial cells (EC) is selectively increased during inflammation. The mechanisms underlying monocyte-EC interaction indicated the involvement of surface-adhesion molecules on monocytes and EC. In earlier studies we noticed that the monocyte-specific mAb, designated mAb 63D3, in contrast to mAb against the beta 2-integrin molecules, inhibited the monocyte binding to monolayers of rIL-1 alpha-stimulated venous EC. The aim of the present study was to further characterize the Ag recognized by mAb 63D3 and to investigate the specific contribution of this Ag to the adherence of monocytes to cultured human macrovascular venous or arterial EC. Flow cytometric analysis demonstrated that the 63D3 Ag is expressed exclusively on the surface of peripheral blood monocytes. SDS-PAGE analysis of mAb 63D3 immunoprecipitates of 125I-labeled human monocyte surface proteins revealed that the target Ag for mAb 63D3 is a 52- to 55-kDa molecule identical to the myeloid differentiation protein CD14. Stimulation of EC with rIL-1 alpha or rTNF-alpha for 4 or 24 h or rIFN-gamma for 24 h increased (p less than 0.005) the number of monocytes bound to both types of EC. This cytokine-induced increase in monocyte adherence was significantly (p less than 0.0005) inhibited when the monocytes were coated with various mAb against CD14. The binding of monocytes to nonstimulated venous or arterial EC was not inhibited by anti-CD14 mAb. Our results lead to the conclusion that CD14 molecules, which on basis of their structure and m.w. are not related to the beta 2-integrin family of heterodimeric leukocyte adhesion molecules, participate in the binding of monocytes to cytokine-stimulated EC.