Determinant selection and macrophage function in genetic control of the immune response

The immune response to insulin, in both mouse and guinea pig, is under control of H-linked immune response genes. When immunized with either pork or beef insulin in CFA, both strain 2 and 13 guinea pigs respond by antigen-specific lymphocyte proliferation and synthesis of specific antibody. The specificities of the elicited antibodies and indistinguishable between these inbred strains. By constrast, strain 2 T cells recognized a distinct region of the A chain alpha loop consisting of amino acid residues 8, 9 and 10, while strain 13 T cells see an as yet undefined region of the B chain. H2b (A chain alpha loop responder) and H2d (B chain responder) mice similarly discriminate which areas of the molecule are recognized by their T lymphocytes. The function of the Ir gene in both the guinea pig and mouse appears to be an intramolecular selection of discrete regions within the antigen for recognition by the T cell. The data presented suggest that this function operates at the level of the macrophage.

Analogous functions of macrophages and Langerhans cells in the initiation in the immune response

Langerhans cells constitute a minor cell population within the mammalian epidermis. This paper defines these cells immunologically and functionally and supports the concept that Langerhans cells are closely related to cells from the monocyte-macrophage-histiocyte series. Both cell types bear surface receptors for Fc-IgG and C3 and express surface glycoproteins, termed Ia antigens, encoded for by immune-response genes (Ir genes) of the major histocompatibility complex of the species. The expression of Ia antigens by Langerhans cells and macrophages is intimately associated with important functions of both cell types, including the capacity to present immunologically relevant antigen to the T lymphocyte and to cause proliferation to allogeneic T lymphocytes in mixed leukocyte reactions.

Adherent cell function in murine T lymphocyte antigen recognition. I. A. macrophage-dependent T cell proliferation assay in the mouse

The data in this report describe a T cell proliferation assay with nylon wool column-purified murine lymph node lymphocyte from animals immunized by footpad injection of antigen in CFA. It was found that the in vitro immune response of sensitized T cells to soluble protein antigens was functionally dependent on the presence of adherent cells, more specifically macrophages, at all concentrations of in vitro antigen challenge. The response was due to T cells in that cytotoxic treatment of the immune lymphocyte cells with anti-Thy 1.2 serum and complement effectively eliminated the antigen-specific DNA synthetic responses. The antigen-specific proliferation of murine lymphocytes depleted of adhereent cells could not be reconstituted with either guinea pig macrophages nor murine fibroblasts, indicating the existence of species and cell type specificity. In contrast to previous observations in the guinea pig, soluble products of cultured adherent cells could at least partially replace the function of intact macrophages in the response to antigen.

Genetic control of the immune response to insulin: its dependence upon a macrophage mediated selection of distinct antigenic sites

The immune response to insulin, in both mouse and guinea pig , is under control of H-linked immune response genes. When immunized with either pork or beef insulin to CFA, both strain 2 and 13 guinea pigs respond by antigen-specific lymphocyte proliferation and synthesis of specific antibody. The specificity of the elicited antibodies are indistinguishable between these inbred strains. By contrast, strain 2 T cells recognize a distinct region of the A chain alpha loop consisting of amino acids residues 8, 9 and 10, while strain 13 T cells see an as yet undefined region of the B chain. H2b (A chain alpha loop responder) and H2d (B chain responder) mice similarly discriminate which area of the molecule are recognized by their T lymphocytes. The function of the Ir gene, in both the guinea pig and mouse appears to be an intramolecular selection of discrete regions within the antigen for recognition by the T cell. The data presented suggest that this function operates at the level of the macrophage.

Function of macrophages in genetic control of immune responsiveness

Macrophages serve an essential but poorly understood role in the cellular and molecular events that underlie immune competence. Antigenic proteins are now known to bind initially to macrophages prior to their recognition by T lymphocytes. Antigen uptake by macrophages is a metabolism-dependent event that results in an association of the antigen or a fragment thereof with a product of genes linked to the major histocompatibility complex of the species. For recognition of this associative form of antigen and self to result in cell proliferation, a direct physical interaction of antigen-bearing macrophage and lumphocyte must occur. Soluble forms of the altered antigen complexed to self may, however, function in nonproliferative T cell activation phenomenon. Using antigens of defined structure, it is possible to derive data which indicate that genetic control of immune responsiveness resides at the level of the antigen-presenting cell, thus indicating that these latter cells have profound discriminatory influences on host immune competence.

Antigen handling by guinea pig macrophages: further evidence for the sequestration of antigen relevant for activation of primed T lymphocytes

Guinea pig macrophages can take up sufficient 2,4 dinitrophenyl guinea pig albumin during a brief in vitro exposure at 37 degrees C to trigger proliferation and lymphokine production with primed T lymphocytes on subsequent co-culture. Treatment of such antigen-bearing macrophages with trypsin, a procedure which removes surface antigen, does not alter the ability of such macrophage to initiate the release of migration inhibition factor from sensitized T lymphocytes. In addition, formation of antigen-specific rosettes between primed T cells and antigen-bearing macrophages is not blocked by high concentrations of antibody directed against the antigen mediating this interaction. Similarly, primed T lymphocyte DNA synthesis induced by antigen-bearing macrophages is not inhibited by specific antibody to that antigen. These data support the conclusion that the fraction of macrophage-associated antigen which is relevant to T lymphocyte activation does not reside on the macrophage surface but rather remains in a restricted compartment from which it is accessible to the T cell but unavailable to either blockade by specific antibody or removal by proteolytic enzymes.

Determinant selection is a macrophage dependent immune response gene function

Immune response (Ir) genes are linked to the species histocompatibility complex and define as yet uncharacterised phenotypic products which control the immune response to thymus dependent antigens. Antibody formation and antigen induced T lymphocyte proliferation are two examples of immune phenomena which, in vivo and in vitro, operate under Ir gene influence. To clarify their mechanism of action and cellular location, we have examined the contribution of antigen structure (amino acid sequence and conformation to Ir gene control of antigen recognition by T lymphocytes) as well as to the critical role played by the antigen presenting macrophage in expression of that control. We report that immune response gene control of antigen recognition operates at least in part at the level of the macrophage.

Independent populations of primed F1 guinea pig T lymphocytes respond to antigen-pulsed parental peritoneal exudate cells

Thymus-dependent (T) lymphocytes from (2 x 13)F1 hybrid guinea pigs immunized to ovalbumin (OVA) in complete Freund's adjuvant can be stimulated to proliferate in vitro by antigen-pulsed peritoneal exudate cells (PECs) derived from either strain 2 or strain 13 donors. In this communication, we show that the population of primed F1 T lymphocytes which can be activated by antigen-pulsed strain 2 PECs is largely independent of the population of cells that can be activated by antigen-pulsed strain 13 PECs. This was demonstrated by both positive and negative selection procedures. In the former, T lymphocytes from OVA-primed (2 x 13)F1 donors were enriched by initial culture with OVA-pulsed strain 2 or strain 13 PECs for 1 wk. Cells selected by culture with OVA-pulsed strain 2 PECs responded well to OVA-pulsed strain 2 PECs and poorly to OVA-pulsed strain 13 PECs. If positive selection had been carried out with OVA-pulsed strain 13 PECs, the selected F1 T cells responded well to OVA-pulsed 13 PECs and poorly to OVA-pulsed 2 PECs. Negative selection was achieved by short term culture with antigen-pulsed PECs and by eliminating proliferating cells by treatment with bromodeoxyuridine and light. This procedure demonstrated that the population of primed F1 T lymphocytes which are responsive to OVA or to purified protein derivative of tuberculin can be divided into subpopulations uniquely responsive to antigen on either strain 2 or strain 13 PECs. Evidence was presented to indicate that this selective responsiveness was not the result of the action of alloantigen-specific suppressor cells. The results are considered in terms of current concepts of the genetic and molecular regulation of the interaction of PECs and T lymphocytes.

Immune response gene control of determinant selection. I. Intramolecular mapping of the immunogenic sites on insulin recognized by guinea pig T and B cells

T-cell DNA synthesis and T-helper cell function in response to isolated insulin chains and naturally occurring insulin variants was assessed in insulin immune guinea pigs. Two distinct antigenic determinants, recognized by T cells, were defined. One localized in the B chain and the other one constituted by amino acids A8, A9, and A10 of the insulin A-chain loop. Recognition of the B-chain determinant is under the control of Ir genes linked to the strain 13 major histocompatibility complex. This was shown by studying the response to isolated insulin B chain in F1(2 x 13) guinea pigs, as well as serologically defined backcrosses and outbred animals. Insulin recognition through the A-chain loop determinant is specific for strain 2 guinea pigs. These animals recognize this region of the molecule even when displaying different amino acid sequences. The strain differences observed in those antigenic sites eliciting T-cell recognition was not found at an antibody level. No differences could be detected in the ability of the different insulin variants to inhibit the binding of 125I-labeled pork insulin to strain 2 guinea pig anti-pork insulin or to strain 13 guinea pig anti-pork insulin.

The induction and regulation of guinea pig B-lymphocyte proliferation in vitro

Conditions for the in vitro induction of proliferation have been examined in a population of guinea pig lymph node lymphocytes enriched for B lymphocytes. Known B cell mitogens such as bacterial lipopolysaccharide and tuberculin-purified protein derivative induced DNA synthetic responses in this B lymphocyte population as did a number of dinitrophenyl hapten-protein conjugates, all in the apparent absence of T cell participation. B cell proliferation occurred most efficiently in serum-free medium with both heterologous and homologous sera inhibiting maximum responses. In vivo immunization with hapten-protein conjugates failed to enhance subsequent in vitro B cell responsiveness to these materials beyond that owing to recruitment by contaminating antigen-primed T cells. Macrophage-associated antigen, which efficiently triggered T cell proliferation was much less effective at initiating B cell DNA synthesis than was soluble antigen not bound to macrophages. Furthermore, although accessory cells were required for the development of T cell DNA synthetic responses, macrophages of factors produced by them inhibited spontaneous or induced B cell 3H-thymidine incorporation.

Macrophage-lymphocyte interaction. III. Site of alloantiserum inhibition of T lymphocyte proliferation induced by allogeneic or aldehyde-bearing cells

Inhibition by anti-Ia sera of guinea pig T lymphocyte proliferation induced by allogeneic macrophages (MLR) and NaIO4 or neuraminidase-galactose oxidase-treated macrophages has been investigated in order to identify the target cell upon which the antisera act. Anti-2 and anti-13 alloantisera were found to inhibit both MLR and aldehydeinduced T cell reactivity when directed against the specificity of the stimulatory macrophage. Little or no inhibition was observed when these antisera were directed against the T lymphocyte specificity when cultures were harvested at the time of peak proliferation. In addition, anti-2 serum was found to inhibit macrophage-lymphocyte rosett formation at 20 hr between neuraminidase-galactose oxidase-treated strain 2 macrophages and strain 13 lymphocytes. These findings demonstrate that inhibition of T cell proliferation can be produced by anti-Ia sera directed against the macrophage and raise the possibility that Ir gene products may function in part at the level of the macrophage.

Phytohemagglutinin-induced proliferation of guinea pig thymus-derived lymphocytes. II. Accessory cell function

Accessory cell participation in PHA-induced thymus-derived lymphocyte DNA synthesis encompasses two distinct functions. The first consists of maintenance of the functional integrity of resting lymphocytes, and the second involves the direct induction and/or support of T cell proliferation in response to this mitogen. Whereas the reducing agent 2-mercaptoethanol can support an Mphi-depleted population of resting lymphocytes so that the latent biologic activity is maintained, it is not itself sufficient to allow the induction of lymphocyte proliferation in response to PHA. This latter function requires intact accessory cells.

Spontaneous and induced membrane hyperpolarizations in macrophages

The electrophysiological properties of guinea pig peritoneal macrophages cultured in vitro were studied using standard intracellular recording techniques. The mean transmembrane potential, input resistance and time constant recorded from these cells were -13.1 mV, 143 Mohms, and 18 msec respectively. The majority of macrophages exhibited spontaneous hyperpolarizations (HA) of 4-8 seconds in duration and 10-50 mV in amplitude. Mouse peritoneal macrophages and human monocyte-derived macrophages manifested similar HA. HA could be induced by either mechanical stimulation or application of hyperpolarizing currents of 2-8 namps. HA had a mean reversal potential of -53 mV. Increasing the extracellular [K+] 10-fold resulted in a 50 mV shift in reversal potential. Addition of EGTA (1.5 mM) inhibited both spontaneous and evoked macrophage HA in the presence of excess Mg++. The divalent cation ionophore, A23187 induced prolongation of HA at low concentration (0.6 X 10(-6) M) and resulted in sustained hyperpolarization at higher concentration (2.0 X 10(-6) M). Addition to EGTA to cells treated with A23187 abolished HA. These data indicate that: (1) cultured macrophages from a variety of species exhibit spontaneous and induced HA, (2) development of HA is related to an increase in membrane permeability to K+, and (3) Ca++ may regulate the spontaneous and evoked electrical activity of the macrophage membrane presumably by affecting K+ permeability.

Isolation and partial characterization of human eosinophil granules. Comparison to neutrophils

Human blood eosinophils obtained from untreated patients with large numbers of circulating eosinophils were purified and lysed. An eosinophil contains 2.65 times as much peroxidase, 2.44 times as much beta-glucuronidase, approximately two times as much acid beta-glycerophosphatase, and 1.2 times as much protein as a neutrophil. Lysate filtration allowed isolation of eosinophil granules by isopycnic ultracentrifugation in sucrose. The granules had a mean density of rho 1.24 g/ml, and contained peroxidase, beta-glucuronidase, and acid beta-glycerophosphatase. They totally lacked muramidase and alkaline phosphatase. Electron micrography confirmed the isolation.

Temporal dependence of the inhibition by cytochalasin B of antigen-initiated migration inhibition factor production

The effects of cytochalasin B on the antigen recognition process have been examined using an in vitro assay of macrophage-inhibition factor (MIF) production by activated guinea pig T lymphocyte-enriched populations. The data indicate that cytochalasin B inhibits MIF production if added at the initiation of culture but not if added 2 hr after antigen. These data are interpreted as consistent with either an inhibition by cytochalasin B of the physical assoication of antigen-bearing marcrophage and lymphocytes or with an inhibition of the access of antigen to the T lymphocyte receptor.

The requirement for macrophage-lymphocyte interaction in T lymphocyte proliferation induced by generation of aldehydes on cell membranes

Guinea pig T lymphocyte proliferation induced by sodium periodate (NaIO4) or neuraminidase-galactose oxidase (NG) occurs when lymphocytes and macrophages are cultured together after treatment of either purified T lymphocytes or macrophages with these agents. Regardless of which cell initially bears the modified surface carbohydrate, lymphocyte proliferation requires the presence of viable homologous macrophages and fails to occur when they are replaced with fibroblasts, erythrocytes, L2C leukemia cells, thymocytes, PMN, line I hepatoma cells, or murine macrophages. Lymphocyte proliferation resulting from NaIO4 or NG treatment of lymphocytes is diminished when these cells are treated with proteolytic enzymes or aged in in vitro culture for 48 hr. By contrast, proteolytic enzyme treatment or in vitro aging has no effect on the ability of NaIO4 or NG-treated macrophages to induce lymphocyte proliferation. The requirement for macrophage-lymphocyte interaction in NaIO4 or NG-induced lymphocyte proliferation is indicative of a central role for the macrophage in the initiation of T lymphocyte proliferation.

Inhibition of macrophage-lymphocyte interaction by cytochalasin B during antigen recognition by T lymphocytes

The effects of cytochalasin B on functional and physical macrophage-lymphocyte interaction have been examined. Cytochalasin B, an inhibitor of a variety of membrane activities blocks antigen-dependent bindings of immune lymphocytes to macrophages and antigen-triggered lymphocytes proliferation if added at the initiation of culture. Cytochalasin B becomes progressively less inhibitory if addition is delayed by increasing intervals from the onset of culture. Under these conditions neither antigen handling by macrophages nor the proliferative response of lymphocytes to PHA is inhibited by cytochalasin B. These data are interpreted to suggest that cytochalasin B inhibits antigen-specific macrophage-lymphocyte interaction either by inhibition of an initial antigen-independent phase of macrophage-lymphocyte interaction or by interfering with a lymphocyte membrane event necessary for the interaction of the antigen-specific lymphocyte receptor with the macrophage-bound antigenic signal.

Macrophage-lymphocyte interaction: antigen-independent binding of guinea pig lymph node lymphocytes by macrophages

The antigen independent binding of guinea pig lymph node lymphocytes by glass-adherent macrophages was investigated. Binding was found to be mediated by a trypsin digestible, divalent cation-dependent, temperature-sensitive macrophage receptor mechanism that was not competitively inhibited by excess immunoglobulin. Data are presented to indicate that in the absence of antigen, macrophages were capable of binding both thymus-derived and bone marrow-derived lymphocytes without apparent selectivity, and further, that the binding of neither cell was mediated by surface membrane-associated immunoglobulin.

Macrophage-lymphocyte interaction and antigen recognition

The functional and morphologic aspects of immunologically relevant macrophage-lymphocyte interaction have been characterized in inbred guinea pigs. Antigen-dependent initiation of in vitro DNA synthesis in lymphocytes taken from animals previously immunized with that antigen has been shown to be macrophage dependent. Expression of this in vitro correlate of in vivo established cellular immunity requires that antigen is initially bound to macrophages antecedent to any interaction with the specific lymphocyte. In view of the failure of supernatants from macrophages briefly exposed to antigen to initiate DNA synthesis in immune lymphocytes and the critical density requirements for lymphocyte proliferation, it is reasonable to assume that a direct physical interaction occurs between the antigen-bearing macrophage and lymphocyte. Using an in vitro assay of lymphocyte binding to macrophage monolayers, we have characterized what appear to be sequential events in macrophage-lymphocyte interaction. The initial event is an antigen-independent interaction between macrophage and lymphocyte whose characteristics are rapid reversibility, species but not strain specificity, and dependence on macrophage metabolism. If macrophages bear antigen for which a given lymphocyte possesses a specific receptor, then a second nonreversible antigen-dependent stabilization of binding occurs. This latter step requires tht macrophage and lymphocyte be histocompatible. These observations parallel functional studies of the histocompatibility dependence of macrophage-associated antigen initiation of lymphocyte DNA synthesis in guinea pigs. A model sequence of the physical events correlating with functional macrophage-lymphocyte interaction is proposed.

Quantitative and immunologic aspects of the handling of 2,4 dinitrophenyl guinea pig albumin by macrophages

Studies correlating quantitative aspects of the handling of dinitrophenyl guinea pig albumin (DNP-GPA) by guinea pig macrophages with the potential of cell-associated antigen to initiate proliferation of immune T lymphocytes have examined the nature of immunologically relevant antigen. After the loss of 75% of cell-bound DNP-GPA during the first 24 hr of in vitro culture, the remaining antigen persists qualitatively unchanged throughout further culture. However, coincident immunogenicity of the macrophage-associated NDP-GPA progressively deccreases, suggesting loss of accessibility of the antigen to responding immune lymphocytes. There is a small, stable, surface antigen pool but these studies suggest that the immunologically critical fraction of DNP-GPA, as regards guinea pig T cell activation, is resistant to trypsinization and inaccessible to antibody.

Macrophage activation of allogeneic lymphocyte proliferation in the guinea pig mixed leukocyte culture

The role of the macrophage in the guinea pig mixed leukocyte culture was investigated. Macrophages obtained from oil-induced peritoneal exudates, peritoneal wash-out cells, spleen, and alveolar washings were found to be effective stimulators of allogeneic lymph node and splenic lymphocyte DNA synthesis. The stimulatory properties of macrophages proved radioresistant but viability dependent. Unfractionated lymph node cells or adherence column purified lymph node lymphocytes and thymocytes were only minimally active as stimulators, even in the presence of macrophages syngeneic to the responder lymphocytes. Allogeneic fibroblasts, polymorphonuclear leukocytes, L2C leukemia cells, and xenogeneic (murine) macrophages failed to simulate. These data provide evidence that the macrophage is the predominant stimulator of the mixed leukocyte culture in the guinea pig.

Macrophage-lymphocyte interaction. II. Antigen-mediated physical interactions between immune guinea pig lymph node lymphocytes and syngeneic macrophages

The effect of specific antigen on the development of physical interactions between lymph node lymphocytes (LNL) obtained from animals which had been immunized to that antigen and macrophages was examined. We found that the presence of antigen, either limited to the macrophage () or free in the medium, profoundly increased the degree of ) or free in the medium, profoundly increased the degree of Mphi-LNL interaction observed. This enhanced interaction was dependent on the coincidence in the cultures of Mphi bearing antigen and LNL from animals specifically immunized to that antigen. Although antigen-independent interactions developed equally well between syngeneic and allogeneic combinations of lymphocytes and macrophages, antigen mediated interactions required that macrophages and lymphocytes be syngeneic. Prolongation of antigen-mediated Mphi-LNL interactions resulted in the induction of LNL DNA synthesis, initially involving those lymphocytes physically associated with antigen-bearing Mphi. These studies are interpreted to indicate that physical interaction between immune lymphocytes and antigen-bearing Mphi represents a morphological correlate of the functional activation of immune lymphocytes. Further, it is suggested that the physical events involved in lymphocyte proliferation may proceed sequentially from antigen-independent reversible binding of lymphocytes by macrophages to prolonged antigen-stabilized interaction eventuating in the triggering of specifically immune lymphocytes.

Separation and characterization of human neutrophil granules

Human blood neutrophilic leukocytes were separated and purified by modifications of the Hypaque/Ficoll and dextran separation methods, resulting in a suspension which was greater than 96% neutrophils. Neutrophils were prepared in 0.34 M sucrose containing heparin and were clarified of nongranular debris by sequential passage through polycarbonate filters of pore size 5 mu and 2 mu. Isopycnic sucrose gradients of such filtrates revealed three major bands. The gradient separated fractions were studied by electron microscopy including peroxidase cytochemistry and by enzyme assay for myeloperoxidase (MPO), beta-glucuronidase, muramidase alkaline phosphatase and acid phosphatase utilizing both p-nitrophenylphosphate (pnp) and beta-glycerophosphate as substrates. Peroxidase-positive granules were observed at both density 1.22 (band A) and density 1.20 (band B). Three peroxidase-negative granules were identified: the round or oval peroxidase-negative granule of density 1.22 (band A) and two smaller granules, distinguishable by size and shape at density 1.18 (band C). Band C granules contain crystalloid inclusions. Peaks of muramidase activity coincided with bands A and C, suggesting the presence of muramidase in the peroxidase-negative granules of density 1.22 and in one or both of the peroxidase-negative granules at density 1.18. beta-Glucuronidase was distributed like MPO, with a major peak in band B and a minor peak in band A. Acid beta-glycerophosphatase was largely in band A. Acid pnp phosphatase was nonspecifically associated with soluble nongranular protein which always remained at the origin of sucrose gradients. Alkaline phosphatase was not granule associated and sedimented alone to density 1.145, which is highly suggestive of a cytoplasmic membrane localization for this enzyme.