A monoclonal antibody to a differentiation antigen present on mature human macrophages and absent from monocytes

A monoclonal antibody is described that has been generated in the mouse against cultured human blood monocytes/macrophages. The antibody, designated 25F9, belongs to the IgG1 subclass, detects antigens of m.w. 86,000, and does not react with freshly isolated blood monocytes but reacts with monocytes after 3 days of culture. The expression of the 25F9 antigen on macrophages increases with culture time. Furthermore, the antibody is negative on platelets, granulocytes, lymphocytes, and a large number of human cell lines except the two melanoma lines MeWo and Mel 57. In cryostat sections of normal human tissue (skin, lung, liver, thymus) and of inflammatory or neoplastic tissue (cutaneous lymphoma, eczema, BCG-granuloma, and melanoma), the antibody reacts with scattered macrophages in the dermis but not with epidermal Langerhans cells, with alveolar macrophages, with liver Kupffer cells, and with scattered macrophages in the cortex and medulla of thymus. In eczema, BCG-granuloma, and cutaneous lymphoma, only a few infiltrating macrophages were stained. On the other hand, a large number of macrophages and melanophages reacted positively in melanoma. In some cases melanoma cells also stained weakly positive. Thus, the antibody detects a differentiation antigen preferentially expressed on mature, tissue-fixed macrophages and absent from blood monocytes.     

A monoclonal antibody to a novel differentiation antigen on human macrophages associated with the down-regulatory phase of the inflammatory process

A monoclonal antibody (RM3/1), raised by immunizing mice with human monocytes, is described which detects a surface antigen on about 20% of freshly isolated peripheral blood monocytes and is increasingly expressed upon cultivation, reaching a maximum between day 2 and 3. By incubation of monocytes with interferon-gamma, 12-O-tetradecanoylphorbol-13-acetate and lipopolysaccharide, antigen expression is decreased but strongly enhanced after incubation with dexamethasone. In cryostat sections of normal tissue, the antibody detects histiocytes in the skin, Kupffer cells in the liver, few alveolar macrophages in the lung, macrophages in the red pulp of the spleen and in the cortex of the thymus, and many macrophages in the placenta. In acute inflammatory tissue, e.g. gingivitis, the antigen is preferentially expressed by macrophages appearing late in the inflammatory process. In chronic inflammation, e.g. BCG granulomas and rheumatoid arthritis, RM3/1-positive macrophages are seen to varying degrees. Double-staining experiments with the antigen 25F9, specific for resting mature macrophages, revealed that RM3/1 and 25F9 are expressed by distinct populations in normal and acute inflammatory tissues. From this it is concluded that the antibody RM3/1 specifically detects a macrophage phenotype which seems to be associated with the healing phase of the inflammatory process.     

Production and characterization of a monoclonal antibody (A1-3) that binds selectively to activated monocytes and inhibits monocyte procoagulant activity

We describe the generation and characterization of a new monoclonal antibody, A1-3, which possesses two unique properties. First, A1-3 binds selectively to stimulated human monocytes. Secondly, A1-3 inhibits the procoagulant activity expressed by stimulated monocytes and by human brain tissue factor. Unstimulated human peripheral blood cells (granulocytes, lymphocytes, monocytes, red blood cells, and platelets), prepared in the absence of detectable endotoxin, express no procoagulant activity and fail to bind A1-3. Stimulation of peripheral blood monocytes. alveolar macrophages, or the monocyte-like cell line U937, however, results in the expression of procoagulant activity and the binding of A1-3. The surface antigen recognized by A1-3 was recovered from endotoxin-stimulated human monocyte vesicles by immune precipitation and demonstrated an apparent m.w. of approximately 52,000. It is proposed that the monoclonal antibody A1-3 detects a differentiation antigen on human monocytes that is expressed in response to stimuli for monocyte activation.     

Macrophage colony-stimulating factor enhances monocyte and macrophage antibody-dependent cell-mediated cytotoxicity

In vitro culture of either human peripheral blood monocytes or murine peritoneal macrophages for 72 hr in the presence of macrophage colony-stimulating factor (M-CSF) dramatically increased their subsequent ability to mediate antibody-dependent cellular cytotoxicity (ADCC). The M-CSF-treated cells were more effective in ADCC at lower effector to target cell ratios and in the presence of lower concentrations of tumor-specific monoclonal antibody than the untreated control cells. Two other hematopoietic cytokines, granulocyte-macrophage colony-stimulating factor and interleukin-3, reported to enhance other macrophage effector functions were ineffective in promoting the development of ADCC by cultured human monocytes. All three hematopoietic growth factors were capable of enhancing the ability of the cultured monocytes to secrete TNF alpha; however, TNF alpha is unlikely to be an important cytotoxic factor in ADCC because neutralizing antibodies against TNF alpha had no affect on ADCC in vitro. Further, much higher concentrations of M-CSF were required to augment monocyte TNF alpha release (20-100 ng/ml) than ADCC capacity (1-10 ng/ml). These results suggest that M-CSF administration might prove effective in increasing the tumoricidal activities of tumor-specific monoclonal antibodies by enhancing the capacity of monocytes and macrophages to mediate ADCC.     

Human recombinant migration inhibitory factor activates human macrophages to kill tumor cells.

A recombinant form of human migration inhibitory factor (rMIF) obtained from COS-1 cells transfected with MIF-specific cDNA is able to activate cultured human peripheral blood monocytes and monocyte-derived macrophages, in a dose-dependent manner to become cytotoxic for tumor cells in vitro. The cytotoxicity exhibited by macrophages treated with rMIF is > or = 30% above that of cells incubated with control supernatants or with media and peaks 72 hr after the addition of tumor targets. rMIF also induces macrophages to produce tumor necrosis factor (TNF-alpha) and interleukin-1 beta (IL-1 beta). These results demonstrate that rMIF is able to modulate macrophage functions and plays a role in cell-mediated immune response.     

Aggregation in Dictyostelium discoideum

Cultured peritoneal macrophages have previously been shown to release a potent mitogen for mesenchymal cells. Peritoneal macrophages are derived from peripheral blood monocytes, one of the principal inflammatory cells associated with numerous tissue responses to injury. Cultured human monocytes can be activated by endotoxin or concanavalin A to secrete a potent growth factor(s) that is active on human smooth muscle cells, human fibroblasts and 3T3 cells. The optimal conditions for activation of monocyte release of this monocyte-derived growth factor(s) (MDGF) were to expose 5-day-old monocyte cultures (initially plated at 6.8 × 10⁵ cells/ml medium) to 10 μg/ml endotoxin or 6 μg/ml concanavalin A for approximately 20 hr. Monocytes can secrete MDGF into serum-free medium supplemented with 0.15% bovine serum albumin. MDGF stimulates both DNA synthesis and increase in cell number and is trypsin-sensitive, heat labile and nondialyzable. The relationship of MDGF to other monocyte products and its potential importance in wound repair and atherogenesis are discussed.     

A bovine 'Ia-like' antigen detected by a xenogeneic monoclonal antibody

A monoclonal antibody termed B2 Val 7C7, was produced by the fusion of xenoimmune mouse spleen cells with Sp2/0.Ag 14 myeloma cells. This antibody is specific for a polymorphic lymphocyte antigen; it was detected on cells from 138 out of 177 cattle by both 125I-labelled protein A (solid-phase radioimmunoassay, SPRIA) and gold-labelled protein A (immunogold). Its binding was tested on various cell types (peripheral blood lymphocytes, monocytes, polymorphonuclear cells (PMN), thymocytes) from a variety of normal bovine donors. On the one hand, B2 Val 7C7 detects a determinant present on all IgG-bearing lymphocytes, on 20% of the non-IgG-bearing lymphocytes and on the majority of the monocytes. On the other hand, no binding occurs on any PMN or thymocytes. The detected membrane antigen was isolated by immunoprecipitation from an NP 40 extract of 3H-leucine-labelled cells. On SDS-PAGE, it appears to be composed of two sub-units: a 32 000-dalton and a 27 000-dalton chain. These results show that B2 Val 7C7 recognizes an alloantigenic specificity present on an Ia-like antigen.     

A monoclonal antibody against an antigen present on mouse macrophages and absent from monocytes

Summary A monoclonal antibody (BM8) raised in the rat against cultured mouse bone marrow-derived macrophages reacted only with macrophages and not with granulocytes, mast cells, platelets, lymphocytes, fibroblasts, and endothelial cells. BM8 did not detect blood monocytes. In cultured bone-marrow cells, expression of BM8-antigen was found on a few macrophages after one day of culture and reached its maximum level with 80% positive macrophages after 7–10 days of culture. The antibody BM8 belonged to the IgG_2a subclass, was non-cytotoxic and directed against a 125 kD membrane antigen. In cryostat sections of normal mouse tissues (spleen, lymph node, thymus, liver, skin) BM8 detected tissue-fixed macrophages and Langerhans cells in the skin. In spleen and lymph node, BM8 reacted with macrophages in the red pulp and in the medullary cords, respectively, but not with heavily phagocytosing marginal-zone macrophages, as revealed by in-vivo phagocytosis of colloidal carbon. In granulomata induced by complete Freund's adjuvant, BM8 detected inflammatory macrophages but not epithelioid cells. Thus, antibody BM8 detected a differentiation antigen expressed only on mature, tissue-fixed macrophages.     

Monoclonal antibodies that inhibit activation and proliferation of lymphocytes. I. Expression of the antigen on monocytes and activated lymphocytes

It has been shown previously that HBJ127 and HBJ98 monoclonal antibodies raised against a human bladder cancer cell line, and B3 monoclonal antibody against a rat bladder cancer cell line recognized unique cell surface antigens abundant in proliferating cells of the corresponding species. Distribution of the antigens and kinetics of the appearance on human and rat lymphoid cells were examined by means of flow cytometry. Rat macrophages and human peripheral blood monocytes were stained strongly with the B3 and HBJ127 monoclonal antibodies, respectively. With regard to lymphocytes, the expression of the B3-defined antigen on rat lymphocytes was found to have a negative correlation with the maturation of the lymphocytes; the antigen was most abundant in bone marrow cells, less abundant in thymocytes, and least abundant in spleen, lymph node, and peripheral blood lymphocytes. Similarly, the HBJ127-defined antigen on human peripheral lymphocytes was negligible. On activation with Con A or alloantigens, however, both rat and human T lymphocytes did strongly express these antigens. Activation of human or rat B cells with lipopolysaccharide also resulted in the augmented expression of these antigens. Kinetics studies revealed that the antigen expression was readily manifested within 12 hr on activation of rat or human T cells with Con A, was augmented progressively with culture time, and reached a plateau within 36 hr. This somewhat earlier appearance of these antigens apparently preceded the manifestations of the IL 2 receptor (Tac antigen) and the augmented DNA synthesis. The B3-defined antigen on Con A-stimulated T cells was more rich on the lymphocytes in S and G2/M phases than those in G1 phase, and the expression was not significantly affected by the addition of hydroxyurea, but was moderately inhibited by the addition of sodium butylate. These results suggest that the appearance and expression of the B3-defined antigen and probably also those of the HBJ127/HBJ98-defined antigen are correlated with lymphocyte activation and subsequent progression through the cell cycle.     

Isolation and characterization of monoclonal antibodies reactive with endothelial cells

Monoclonal antibodies were generated to antigens on cultured human umbilical vein endothelial cells. Spleen cells from BALB/c mice, immunized with low passage cultures of human umbilical vein endothelial cells, were fused with the non-secretory myeloma line, P3 x 63Ag 8.653. Hybridoma supernatants were screened for the desired immunological reactivity using ELISA binding assays. Hybridomas secreting antibodies reacting with the immunizing endothelial cells, but not with peripheral blood mononuclear cells, were cloned by limiting dilution and three stable clones were chosen for study. Further testing by ELISA revealed that each antibody displayed a unique pattern of reactivity. One antibody, 14E5, reacted with the macrophage-like cell line DHL-2, cultured macrophages derived from peripheral blood monocytes, and macrophages derived from malignant effusions. The antibody failed to react with fibroblasts or bovine endothelial cells. The second antibody, 12C6, reacted with human and primate fibroblasts and endothelial cells derived from bovine arteries, but not with mature macrophages. The third clone, 10B9, reacted only with the immunizing endothelial cells and the immature-macrophage line U-937. All three antibodies failed to react with long-term human B or T lymphoblastoid cell lines, leukemic cell lines, or murine macrophage lines. None of the antibodies reacted with a battery of human epithelial derived cell lines or primary cultures of human epithelial cells. Indirect immunofluorescence assays revealed that the antigens were expressed on the cell surface. These antibodies should prove useful as differentiation markers of human endothelial cells and in studies of endothelial cell function.     

A bovine 'Ia-like' antigen detected by a xenogeneic monoclonal antibody

A monoclonal antibody termed B2 Val 7C7, was produced by the fusion of xenoimmune mouse spleen cells with Sp2/0.Ag 14 myeloma cells. This antibody is specific for a polymorphic lymphocyte antigen; it was detected on cells from 138 out of 177 cattle by both ¹²⁵I-labelled protein A (solid-phase radioimmunoassay, SPRIA) and gold-labelled protein A (immunogold). Its binding was tested on various cell types (peripheral blood lymphocytes, monocytes, polymorphonuclear cells (PMN), thymocytes) from a variety of normal bovine donors. On the one hand, B2 Val 7C7 detects a determinant present on all IgG-bearing lymphocytes, on 20 % of the non-IgG-bearing lymphocytes and on the majority of the monocytes. On the other hand, no binding occurs on any PMN or thymocytes. The detected membrane antigen was isolated by immunoprecipitation from an NP 40 extract of ³H-leucine-labelled cells. On SDS-PAGE, it appears to be composed of two sub-units: a 32 000-dalton chain and a 27 000-dalton chain. These results show that B2 Val 7C7 recognizes an alloantigenic specificity present on an Ia-like antigen     

Tumor-stimulated release of tumor necrosis factor-alpha by human monocyte-derived macrophages.

Tumor necrosis factor-alpha (TNF) release by monocytes and macrophages may be an important determinant of the physiologic response of the host to neoplastic disease; however, the mechanisms which regulate TNF release by macrophages in hosts with neoplastic diseases are poorly understood. The purpose of this study was to determine if cell membranes and growth medium from human leukemia cell lines and solid tumor cell lines induced TNF release by cultured human blood monocyte-derived macrophages. The capacity for TNF release and direct tumor killing was highest in monocytes cultured for 7 to 11 days. Cell membranes and culture media from K562 erythroleukemia and several small cell lung carcinoma cell lines, including H82, induced the release of up to 1500 TNF units per 10(6) macrophages over 24 hr. By contrast, allogeneic peripheral blood lymphocytes, cell membranes from normal mixed donor peripheral blood leukocytes, or growth medium from normal embryonic lung fibroblasts induced the release of little or no TNF during culture up to 24 hr, suggesting that this macrophage response was specific for tumor cells. Release of TNF by tumor-stimulated macrophages was gradual, peaking 24 hr following the addition of stimuli. Induction of macrophage TNF release was concentration dependent, with half-maximal TNF levels induced by 12.5 and 25 micrograms/ml cell membranes prepared from K562 and H82, respectively. Pretreatment of tumor cell membranes with polymixin B, which inhibits many of the actions of endotoxin, failed to neutralize tumor induction of TNF, suggesting that endotoxin was not responsible for this activity. Depletion of macrophages by treatment with 3C10 monoclonal antibody and complement abrogated tumor-induced TNF release, indicating that macrophages were the source of the secreted TNF. HPLC analysis of H82 growth medium demonstrated a single peak of macrophage activating activity with approximate 40-kDa molecular weight. We have demonstrated that cell membranes and growth medium from some human leukemia and solid tumor cell lines, but not from normal human cells, induce human peripheral blood monocytes and monocyte-derived macrophages to release functionally active TNF. This process may contribute to the host response to some neoplastic diseases.     

Mechanism of human monocyte activation via the 40-kDa Fc receptor for IgG

It is shown that a mAb specific for the human 40-kDa FcR (FcRII) leads to activation of human monocytic cells but that extensive cross-linking of the receptor is required. Calcium mobilization can be induced in immature monocytic cells (undifferentiated U937 cells) and peripheral blood monocytes with an intact IgG1 anti-FcRII antibody (CIKM5) but not by F(ab')2 fragments of this antibody. The intact antibody can bind in a tripartite manner by its two F(ab') sites and its Fc-binding site whereas the F(ab')2 fragments of this antibody can only bind in a divalent fashion. A rise in intracellular free calcium ion concentration occurs when F(ab')2 fragments are cross-linked with F(ab')2 anti-mouse Ig indicating that more extensive cross-linking of FcRII is required rather than an obligatory requirement for an Fc-FcRII interaction. Calcium mobilization in response to intact or cross-linked F(ab')2 fragments of CIKM5 is associated with superoxide production only in IFN-gamma-primed peripheral blood monocytes and IFN-gamma differentiated U937 cells indicating that the activation signal produced via FcRII is inadequate to fully stimulate non-"primed" cells. A second mAb reactive with FcRII (2E1) does not cause calcium mobilization in monocytes or U937 cells, and partially blocks the effects of CIKM5. 2E1 also blocks CIKM5 superoxide production in IFN-gamma-primed monocytes and differentiated U937 cells. This may be explained in part by the fact that 2E1 is an IgG2a antibody and can only participate in bipartite binding with FcRII. When 2E1 is cross-linked with F(ab')2 anti-mouse Ig there is a small calcium response. This does not cause superoxide generation in IFN-primed monocytes but does do so in IFN-gamma differentiated U937 cells. FcRII is also expressed on granulocytes and some B cells but the effects of cross-linking the receptor on these cells differ from those seen in monocytes.     

Expression of E10 antigen on functionally distinct human T-cell subpopulations: comparison with 3A1 defined subsets

Using PWM-driven immunoglobulin synthesis, we studied the regulatory effects of the peripheral blood T-lymphocyte subpopulations defined by the E10 antigen. This previously described antigen (E10) is present on 60% of TPBL, of T4+, and of T8+ cells. The helper activity on PWM-driven B-cell differentiation appears to be highly increased in E10- T cells. This higher capacity does not apparently reflect a different susceptibility to suppressor influences as comparable results were obtained when such suppressor influences are minimized either by removal of T8+ cells from E10- and E10+ T cells, or by removal of monocytes from responding B-cell populations. In contrast, the relative function of T-cell subsets defined by the related antigen 3A1 are influenced by the presence of suppressor cells. It is only in the presence of both T8+ cells and monocytes that 3A1+ cells exhibit a higher inducer effect. Our results suggest that E10 and 3A1 antigens--although showing strong distribution homologies--define different regulatory T-cell populations.     

Effects of human peripheral blood monocytes,monocyte-derived macrophages,and spleen mononuclear phagocytes on Toxoplasma gondii

In vitro effects of human peripheral blood monocytes, peripheral blood monocyte-derived macrophages, and spleen mononuclear phagocytes on Toxoplasma gondii were studied. In almost all instances, over 80% of human monocytes and monocyte-derived macrophages infected with Toxoplasma in vitro destroyed the organism. Degeneration of intracellular Toxoplasma was not due to decreased viability of organisms in the challenge inoculum. Human monocytes did not elaborate into the culture medium substances which altered the capacity of Toxoplasma to survive and replicate within mouse macrophages. The early reduction in intracellular Toxoplasma was not affected by inhibitors of various intracellular processes or by diseases associated with altered cellular immunity (sarcoidosis, infectious mononucleosis, or lymphoma.) The Toxoplasma that remained after 6 hr within human monocytes and macrophages multiplied. This multiplication was observed both microscopically and in a radioassay which detects uptake of [³H]uracil or [³H]deoxyuridine into nucleic acids of intracellular Toxoplasma. Intracellular Toxoplasma in monocytes cultured with poly(I:C) or in monocyte-derived macrophages cultured with lymphokines showed decreased uptake of radiolabeled precursors into nucleic acids of intracellular Toxoplasma. Treatment of monocytes with endotoxin did not alter nucleic acid synthesis of surviving intracellular Toxoplasma. These results suggest that human mononuclear phagocytes in peripheral blood and in tissue (spleen) have the capacity to eliminate a large percentage of the Toxoplasma that they ingest or that invade them. The inhibition of nucleic acid synthesis of remaining Toxoplasma by exposure of monocyte-derived macrophages to lymphokines suggests that lymphocyte products may be important for elimination of the Toxoplasma that remain and multiply within a small proportion of mononuclear phagocytes.     

Anti-T cell monoclonal antibodies in vivo. I. Inhibition of delayed hypersensitivity but not cutaneous basophil hypersensitivity reactions

As part of a study of the therapeutic potential of anti-T cell monoclonal antibodies, we studied the biologic effects of 8BE6, a mouse anti-guinea pig (GP) pan-T cell monoclonal antibody, on blood and tissue T cells and on the prototypic T cell-mediated reactions, classic delayed hypersensitivity (DH) and cutaneous basophil hypersensitivity (CBH). 8BE6 reacts to a 68,000 m.w. protein probably homologous with human CD5 (T1) and murine Lyt-1. A single dose of 1.8 to 3.4 mg 8BE6 caused lymphopenia and greater than 90% depletion of 8BE6+ peripheral T cells 1 to 72 hr later, and a significant but lesser decrease of lymphocytes reacting with another pan-T cell monoclonal antibody (p less than 0.02 at 24 hr). Free serum 8BE6 was detected for up to 48 hr after administration. Immunoperoxidase stains of tissue revealed that lymphocytes in lymph nodes and spleen were coated with mouse immunoglobulin 1 hr after antibody treatment and displayed in situ capping. Subsequently, there was a loss of T cells in all tissues (spleen, lymph node, liver, and kidney) except the thymus, with normal 8BE6 antigen staining returning by 72 hr. Areas of induration of DH reactions to PPD were reduced in 8BE6-treated GP, compared with pretreatment reactions in the same GP or in control-treated GP (p less than 0.001 for both). The numbers of infiltrating T cells and fibronectin-receptor-positive macrophages were also reduced. In contrast, 8BE6 had no effect on CBH reactions, as judged by erythema and basophil counts in 1-micron sections, although fewer T cells were found in reaction sites. There were no differences in IgM, fibronectin, or Ia staining between 8BE6-treated GP and controls. In vivo administration of a single dose of anti-T cell monoclonal antibody results in a transient, highly specific depletion of T cell populations in peripheral blood and tissues except the thymus. This treatment inhibits DH but not CBH reactions by systemic and local depletion of T cells.     

Human mononuclear phagocyte-associated antigens: I. Identification and characterization

Rabbit antisera were produced against a lymphokine-activated human macrophage cell line, U937 (αU937), and human peritoneal macrophages (αPEMØ). After absorption with AB erythrocytes, pooled platelets, and B-lymphoblastoid cell lines, both antisera reacted by microcytotoxicity, indirect immunofluorescence (IF), and radioimmunoassay (RIA) with adherence-purified human peripheral blood monocytes, splenic and peritoneal macrophages, and leukemic myelomonoblasts. A panel of normal human T lymphocytes, B lymphocytes, and erythroid-myeloid or lymphoblastoid cell lines failed to react with both αU937 and αPEMØ. Although both heteroantisera reacted against polymorphonuclear leukocytes (PMNs), after absorption with PMNs specific reactivity against mononuclear phagocytes remained. Absorption of αU937 and αPEMØ with myelomonoblastic leukemia cells (AMML) removed IF and RIA activity against both PMNs and monocytes but not against splenic and peritoneal macrophages. In contrast, absorptions of both heteroantisera preparations with splenic macrophages abolished their IF and RIA reactivity not only to splenic and peritoneal macrophages but also to peripheral blood monocytes and leukemic myelomonoblasts. These results are consistent with (1) both antisera defining specific monocyte/macrophage-associated antigens(s) which are distinct from MHC-coded HLA-A,B,C, and DR antigens, and (2) expression of common monocyte/macrophage-associated antigen(s) and uniquely associated antigen(s) selectively expressed on tissue macrophages. These reagents will be useful in delineating human monocyte/macrophage differentiation as well as the immunological functions of mononuclear phagocytes.     

Species-dependent regulation of monocyte/macrophage Ia antigen expression and antigen presentation by prostaglandin E

The expression of Ia antigen by various murine and human macrophage populations and the ability of prostaglandins of the E series to regulate Ia antigen expression were explored. Monocytes and macrophages from human and murine populations demonstrated a dichotomy in the expression of Ia antigen. Both human monocytes and macrophages expressed elevated levels of Ia antigen compared to their murine counterpart. Murine macrophages appear to express elevated levels of Ia antigen only when actively interacting with T lymphocytes in vivo or with lymphokines in vitro. Prostaglandins of the E series can suppress murine macrophage Ia antigen expression, but have little effect on the expression of Ia antigen by human monocytes and macrophages. Also, prostaglandins of the E series do not modulate the ability of human monocytes to present antigen to autologous lymphocytes when studied over a broad concentration range. These data suggest that prostaglandin E compounds do not profoundly affect human monocyte/macrophage Ia antigen expression or human monocyte antigen presenting activity.     

Recombinant interferon-gamma induces interleukin 2 receptors on human peripheral blood monocytes

The present report describes the inducibility of IL 2 receptors on human peripheral blood monocytes. Although freshly isolated monocytes are IL 2 receptor negative, approximately one-third of the cells react with the anti-Tac antibody within 18 hr of culture. IFN-gamma is found to double both the number of positive cells and the number of binding sites, whereas IL 2 has no influence on the IL 2 receptor expression on monocytes. Anti-Tac precipitates from monocyte lysates several protein bands of similar m.w. to those previously found with activated T and B cells. Finally, IFN-gamma-induced, but not resting, monocytes are found to bind recombinant IL 2. We conclude that IFN-gamma induces peripheral blood monocytes to express IL 2 receptors similar in structure to those found on activated T and B lymphocytes.     

Human ferritin: effects of antigen source and fixation on leucocyte staining by immunoperoxidase technique

The localization of ferritin was studied in peripheral blood cells and variously fixed tissues with the antibodies against ferritins isolated from human heart and spleen. The unlabelled antibody enzyme method (PAP) was used to detect the binding sites of antibodies. In peripheral blood cell smears both antisera gave rise to strong staining of polymorphonuclear (PMN) cell cytoplasm, whereas the monocytes stained relatively weakly. There were no staining differences between the two antisera. In human spleen sections the spleen ferritin antiserum stained the PMN cells and sinusoidal lining cells, whereas the heart ferritin antiserum stained only PMN cells. Neither of the two antisera stained monocytes in the spleen sections. This finding was observed in specimens fixed in Bouin's fixative, Baker's fixative and neutral formalin. However, the immunoreactivity of ferritin was totally destroyed by some other fixatives (Carnoy's fixative, formol sucrose and glutaraldehyde). These results suggest that ferritin is more readily released from monocytes than from PMN cells, and that mature spleen macrophages contain antigenic determinants of ferritin that are recognized only by anti-spleen ferritin antiserum.