Electron microscopic studies of human monocyte and lymphocyte interaction with immunoglobulin- and complement-coated erythrocytes

Cell surface distribution of Fc receptors II and III on living human neutrophils before and during antibody dependent cellular cytotoxicity

Microscopic techniques have been employed to study the cell surface distributions of the immunoglobulin Fc receptors (FcR) II and III on living human neutrophils. Fluorescein-or rhodamine-conjugated monoclonal IgG or Fab fragments directed against FcRII (CDw32) and FcRIII (CD16) were employed to label receptors. FcRII and III were found to be uniformly distributed at neutrophil surfaces during resting conditions. During neutrophil polarization and migration FcRII but not FcRIII preferentially accumulated at the uropod. Sheep erythrocytes (SRBCs) were opsonized with IgG and then incubated with neutrophils. When neutrophils were labeled prior to target addition, FcRII but not FcRIII were found to cluster at the target-effector interface. Little or no clustering of FcRs was observed if labeling was performed after target binding. SRBC oxidation was observed using Soret band illumination during transmitted light microscopy. Time-lapse studies of FcRII distribution and target oxidation were performed. FcRII formed clusters at target effector interfaces prior to target oxidation. Three lines of evidence suggest that clustering is not a general plasma membrane response. Firstly, FcRIII do not cluster lannic acid-modified erythrocytes avidly bound to neutrophils but did not trigger clustering of FcRII. Furthermore, irrelevant neutrophil membrane labels were unaffected by the presence of IgG-opsonized erythrocytes. We suggest that FcRII clustering is one important component leading to the oxidative destruction of target cells.

Influence of immune complexes on macrophage membrane fluidity: a nanosecond fluorescence anisotropy study

Time-resolved fluorescence anisotropy (TRFA) and steady-state anisotropy measurements and fluorescence intensification microscopic observations were made on RAW264 macrophages labeled with 1,6-diphenyl-1,3,5-hexatriene (DPH) or 1-[4-(trimethylammonio)phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH). Microscopic analysis revealed that the fluorescent probe DPH was found in association with plasma membranes and small vesicles. Macrophages treated with immune complexes could not be distinguished from untreated cells, indicating that the same membrane compartments were labeled. The probe TMA-DPH was exclusively localized to the plasma membrane. Steady-state anisotropy measurements indicated that in vitro culture conditions did not significantly affect membrane fluidity. TRFA measurements were conducted to determine the physical properties of macrophage membranes during immune recognition and endocytosis. Data were analyzed by iterative deconvolution to yield phi, the rotational correlation time, and r infinity, the limiting anisotropy. These parameters may be interpreted as the "fluidity" and order parameter of the membrane environment, respectively. Typical values for untreated macrophages were phi = 7.8 ns and r infinity = 0.12. Binding and endocytosis of immune complexes prepared in 4-fold antigen excess increase these values to phi = 22.1 ns and r infinity = 0.15. However, receptor-independent phagocytosis of latex beads decreases these values to phi = 2.2 ns and r infinity = 0.10. Addition of catalase before, but not after, immune complex incubation with cells diminishes the effect upon membrane structure, suggesting that H2O2 participates in fluidity changes. Pretreatment of macrophages with the membrane-impermeable sulfhydryl blocker p-(chloromercuri)benzenesulfonic acid also diminished these effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of the LAI test in bladder cancer patients

To clarify the mechanism of the leukocyte adherence inhibition (LAI) test, 30 bladder cancer patients were studied by the fractionated LAI test in which peripheral lymphocytes were separated into monocyte rich and monocyte deplete fractions. The mean LAI reactivity of 30 bladder cancer patients on the monocyte rich fraction (43.2 +/- 20.3 per cent) was significantly higher than that of the corresponding patients on the standard LAI test (30.4 +/- 12.7 per cent), whereas the mean LAI reactivity of these patients on the monocyte deplete fraction (15.6 +/- 10.7%) was significantly lower than that on the standard LAI test of the same patients (respectively p less than 0.001 and p less than 0.01). It suggests that monocytes play an important role in the capillary LAI test. To further comprehend the mechanism of the LAI phenomenon, indicator cells involved in the LAI test were observed by transmission and scanning electron microscopy. The microvilli on the cell surface of nonadherent monocytes of bladder cancer patients were decreased in number and shortened in length but other populations of nonadherent cells were not remarkably changed. These observations showed that the bladder tumor antigens in extracts from tumors appear to have an influence on the microvilli of monocytes, specifically on monocytes from bladder cancer patients. These morphological changes correlate with the results from fractionated LAI assay and may result in the tumor antigen specific LAI reactivity observed in leukocytes of bladder cancer patients.

A simple procedure for the preparation of rosetted cells for electron microscopy

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Fc receptors on rabbit lymphocytes. Existence of receptors for IgG antibody complexed with antigen; conditions for its detection

The presence of Fc receptors (FcR) on rabbit peripheral blood leukocytes is demonstrated using rosette formation with an ox erythrocyte-antibody (EoxA) complex. The receptor is specific for the Fc fragment of IgG (neither IgM nor F (ab')2 anti-Eox mediates rosette formation) that is antigen-bound (aggregated rabbit IgG inhibits the rosette formation only transiently). The receptor is species-specific: guinea pig IgG/Eox, goat IgG/Eox and sheep IgG/Eox complexes do not show rosette formation, and goat IgG aggregates do not inhibit rosette formation. The origin of the target erythrocytes is of importance. Sheep erythrocytes are not useful, and within Eox large differences between donors were found. Rosette formation was only inhibited by pretreatment of the rosette-forming cells with homologous immune complexes, whereas the size of the antigen greatly influenced the degree of inhibition. The rabbit FcR is pronase-resistant, unlike the human and murine RcR. The interaction of IgG and the FcR is not inhibited by isolated C gamma 3 domains. Further evidence for the requirement of the whole Fc region was obtained in experiments where inhibition of the rosette formation was observed using antisera directed to the C gamma 3 and the C gamma 2 domain, respectively. Anti-Fab antiserum did not inhibit rosette formation. Results are discussed in relation to the mechanism of allotypic suppression.

The characterization and functional significance of plasma membrane Fc Receptors

The importance of various components of the plasma membrane in the generation of the immune response has long been recognized. The identification and characterization of functional membrane receptors are essential for an understanding of the molecular basis of the immune response. The Fc receptor can be operationally defined as a site on the plasma membrane which is capable of binding the Fc portion of IgG. The Fc receptor has been reported on both lymphoid and nonlymphoid cell types. The functional significance of the receptor on these cell populations, as well as the biochemistry of the receptor, is not well established and is currently an important area of investigation. In this review, the Fc receptor will be discussed, primarily in human and murine lymphoid and macrophage cell populations, as a model of membrane immunoreceptors. The review will be divided into four sections. In the first section, consideration will be given to the binding assays used to study Fc receptor-ligand interactions and the class and subclass specificity of the receptor. The possibility of receptor-receptor interaction and quantitation of receptor sites will be discussed. The second phase of the review will be concerned with the fractionation and biochemistry of this receptor system, emphasizing the differences reported in receptor composition from different cell sources. In the third section of the review, the biologic significance of the receptor will be examined. The importance of the Fc receptor in opsonization and phagocytosis by mononuclear phagogytes, B-cell activation, antibody-dependent cell cytotoxicity, and the possible relationship of Fc receptors to the histocompatibility-linked immune response genes will be discussed. Finally, in the fourth section, the possible mechanisms of receptor regulation will be considered. Cell fusion experiments which have been performed and the expression of receptor activity on the hybrid cell clones will be discussed. Receptor regulation at the physiologic level will include the effects of cyclic nucleotide levels and cell cycle on receptor expression. It is the intent of this review to provide a detailed analysis of the Fc receptor and to emphasize its importance in microbiology, cell biology, and immunology.

Hypotonic unmasking of erythrocyte receptor sites

The study reports on plasmalemmal perturbation of erythrocytes under osmotic stress. In comparison with isotonic human erythrocytes a 10 minutes incubation in 150 mosm sodium cacodylate pH 7.4 at 20 degrees C results in an increase of the anti AH P binding rate by a factor of two. 0.1 M N-acetyl galactosamine inhibits the binding of anti-AH P of both isotonic and hypotonic red cells. Contrary to isotonic mouse erythrocytes the agglutination with peritoneal murine leukocytes of hypotonic red cells is greatly enhanced provided the erythrocytes have been incubated in autologous serum. The findings are considered evidence of the unmasking of binding sites due to nonspecific rearrangement of membrane constituents.

Rat endo- and mesothelium lack Fc receptors

The present study is concerned with the interaction of rat endo- and mesothelium with homologous erythrocytes under various conditions of pretreatment and incubation. Its findings show rat endo- and mesothelial cells a) nonadhesive to native or pretreated erythrocytes irrespective of the presence of gamma-globulin in the medium, b) devoid of primary or cryptic receptors sensitive to the Fc segment of the IgG molecule, and c) provided with binding sites at the oxidized glycocalyx which together with receptor groups of modified erythrocytes share the same class of IgG.

Phagocytosis: a review

Primitive unicellular organisms depend greatly on internalization of particulate matter for nourishment. In metazoa, this process is further developed to play a major role in mechanisms of defense. This review analyzes, mainly in mammalian systems, the various phenomena surrounding the phagocytic act. Much of the emphasis is placed on experimental work which has recently elucidated some of its features. Both the structural and functional aspects of phagocytosis are considered throughout the review, which is subdivided into an examination of chemotaxis and the various agents inducing it, the mode of recognition of particles to be phagocytized, and the mechanisms of ingestion. The last includes a discussion of the possible means whereby recognition is translated into ingestion, the modes of adhesion of particles onto the surface of phagocytes, the formation and fusion of pseudopodia during engulfment and ingestion, and process and significance of degranulation. In addition, the metabolic changes in phagocytes during the processes of chemotaxis, ingestion, and digestion are described. A discussion of the various ways phagocytes may destroy microorganisms incorporates an appreciation of the importance of the microbicidal action of the acidic environment of the phagosome, the various lysosomal contents, hydrogen peroxide, superoxide, singlet oxygen, and chemiluminescence. The interdependence and interrelationship of the induction and cooperation of these mechanisms are examined.

II. Ultrastructural differences in attachment patterns of indicator cells to target cells in the rosette-forming process

A comparison was made of the electron microscopic appearances of rosettes formed between mouse spleen lymphocytes and indicator cells with the ligands exposed on their surfaces either in clusters or in continuity. Sheep red blood cells (SRBC) coated with protein A of Staphylococcus aureus or human IgG by the chromium chloride technique were used as indicator cells with cluster distribution of the ligand. RBC coated with rabbit IgG anti-sheep red blood cells or staphylococci were used as indicator cells with uniform distribution of the ligand. Results show that the appearance of the zones of contact (point attachment or broad zone attachment) between lymphocytes and indicator cells are mainly influenced by the distribution of the specific ligands on the surface of the indicator cells and do not reflect the pattern of distribution of receptors on lymphocytes.

Demonstration of the Fc-receptor of blood cells by soluble peroxidase-anti-peroxidase (PAP) complexes

The Fc-receptor of normal human leukocytes, of CLL-cells, and of hematopoietic cell lines was demonstrated with soluble peroxidase-anti-peroxidase (PAP) complexes. In about 9% of normal lymphocytes an almost continuous, strong labeling of the cell membrane was established. Some of these lymphocytes were characterized by a peculiar uniform fine structure. The percentage of PAP-labeled monocytes was in the range of 25%, neutrophils nearly 100%, eosinophils 0%, CLL-cells 10%. Labeled portions of the membrane were interiorized from monocytes. The lymphoid cell-line Daudi established from a Burkitt's lymphoma appeared almost negative, the cell line K562 established from a myeloid leukemia in 75% of the cells strongly positive. PAP-labeling was not influenced by preincubation with trypsine or with neuraminidase; it was negative when PAP-F(ab)2 was used. Results of PAP-labeling were not always in agreement with EA-rosettes or with agg-Ig.

Identification of rosette-forming cells in permanent preparations

A method is described for the identification of leucocytes in permanent cytocentrifuge rosette preparations made with the fluorescent methyl green pyronin-SITS (MPS) staining technique. The percentages of rosettes in stained slides agree well with the results obtained with the conventional haemocytometer method. Application of the MPS staining to cytocentrifuge preparations permits reliable morphological differentiation between free and rosetting leucocytes, and should be particularly valuable in studies on lymphocyte subpopulations in patients.

Ultrastructural studies of leucocytes which form rosettes with homologous erythrocytes in human auto immune haemolytic anaemia

Leucocytes which form rosettes with himologous erythrocytes in auto-immune haemolytic anaemia, infectious mononucleosis and following the stimulation of lymphocyte cultures with PHA have been studied by electron microscopy. The studies showed that the predominant homologous rosette forming cell was lymphocytic and the evidence favoured the conclusion that they were non-immune in nature. This identification does not classify the lymphocyte as thymus or bone marrow derived. Just under half (44%) of the total lymphocytic RFC had perinuclear microfilaments and limited clearing of the plasma of ribosomes close to the cell membrane. These features are consistent with activated T lymphocytes. The remainder of the lymphocytic RFC had no features which allowed their identification as T or B cells. The form of contact between lymphocytic RFC and erythrocyte was mainly of a pointlike nature, with little deformation or invasion of the attached erythrocytes. Monocytes were the only other type of cell encountered with any frequency. Their prime distinguishing feature was the deformation of attached red cells which they caused.

[Haematological and immunological findings in bone marrow aplasia (author's transl)]

The cellularity of the bone marrow, the number of blood cells and the immunoglobulins were investigated in 51 patients suffering from bone marrow aplasia. In this disease not only is a haematopoietic organ disturbed, but disorders of the lymphocyte and of the monocyte-systems can be detected too: the majority of patients show lymphocytopenia and monocytopenia. Immunologic reactions seem to be involved in the pathogenesis of bone marrow aplasia. The plasma cells of the bone marrow are elevated in nearly all of the patients, lymphocytes in every second case. One or several fractions of immunoglobulins are increased in about 50% and diminished in 25% of the patients.

Sheep red cell binding to human lymphocytes treated with neuraminidase; enhancement of T cell binding and identification of a subpopulation of B cells

Neuraminidase treatment of normal human lymphocytes enhances their capacity to form SRBC rosettes; more red cells are bound and the rosettes are more stable. Under these conditions approximately 90% of peripheral blood lymphocytes form rosettes. In addition to the effects on T cells, another population of lymphocytes which possess surface immunoglobulin and have the Fc receptor acquire the rosette-forming property after neuraminidase. This subpopulation of 'B' cells represents approximately half of the lymphocytes with surface immunoglobulin but is not found among the leukemic lymphocytes of patients with chronic lymphocytic leukemia. Electron microscope observations indicate close approximation and intimate association of the red cell and lymphocyte membranes after neuraminidase.