Upregulation of neuropeptides and neuropeptide receptors in a murine model of immune inflammation in lung parenchyma.

The lung is richly supplied with peptidergic nerves that store and secrete substance P (SP), vasoactive intestinal peptide (VIP), and other neuropeptides known to potently modulate leukocyte function in vitro and airway inflammation in vivo. To investigate and characterize neuromodulation of immune responses compartmentalized in lung parenchyma, neuropeptide release and expression of neuropeptide receptors were studied in lungs of antigen-primed C57BL/6 mice after intratracheal challenge with sheep erythrocytes. The concentrations of cytokines in bronchoalveolar lavage (BAL) fluid rose early and peaked on day 1 for interleukin (IL)-2, interferon gamma, and IL-10; days 1 to 2 for IL-6; and day 3 for IL-4, whereas the total number and different types of leukocytes in BAL fluid peaked subsequently on days 4 to 6 after i.

Changes in adhesion molecule expression during distinct patterns of immune cell migration in the inflamed lung.

In response to antigen inhalation, immune cells including alveolar macrophages expressing a VIP1 receptor subtype (VIP1R), lymphocytes and leukocytes participate in the inflammatory event, migrating into and from vascular regions in lung tissue of sensitized mice. To analyze these migratory mechanisms of immune cells, we immunohistochemically examined the expression of the following: cellular adhesion molecules, lymphocyte function-associated antigen-1 (LFA-1) very late activation antigen-4 (VLA-4), and the alpha V (alpha v) subunit and their respective ligands, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and fibronectine; the examination was carried out in pulmonary tissue from days 0, 2, 6 and 12 following intratracheal administration of sheep red blood cells (SRBC) as an antigen to previously sensitized mice. Two days following the antigen challenge, VIP1R-positive macrophages strongly expressing the alpha v integrin subunit were found clustered on the endothelial surface and among the aggregates of perivascularly infiltrated leukocytes.

Role of CD8+ lymphocytes in host defense against Pneumocystis carinii in mice.

An improved understanding of host defense against Pneumocystis carinii could provide novel therapeutic modalities directed against this opportunistic pathogen. Immunodeficient mouse models confirm the role of CD4+ lymphocytes in defense against P. carinii, but the role of CD8+ lymphocytes is controversial.

Neuropeptide signaling of lymphocytes in immunological responses.

Peptidergic nerves in immune organs and lymphoid tissues of the lungs and gastrointestinal tract end on or in close proximity to lymphocytes, mast cells and macrophages. Vasoactive intestinal peptide, substance P and some other neuropeptides, that are recognized by distinct sets of cell surface receptors, regulate aspects of T cell differentiation in the thymus, such as negative selection, and contribute to mediating compartmental immune responses. The latter effects include stimulating expression of adhesive proteins by lymphocytes, enhancement of lymphocyte and macrophage migration in vascular and connective tissues, and modulation of proliferative and synthetic responses of lymphocytes to diverse antigens.

Hypersensitivity pneumonitis.

Although the cause and development of most inflammatory and fibrotic interstitial lung diseases are unknown, both the antigenic stimuli and the immunopathogenic mechanisms that produce the syndrome of hypersensitivity pneumonitis have been well described. Hypersensitivity pneumonitis is a group of related inflammatory and fibrotic interstitial lung diseases that result from hypersensitivity immune reactions to the repeated inhalation of antigens derived from fungal, bacterial, animal protein, and reactive chemical sources. Immune complex-induced inflammatory reactions initiate acute lung injury; T cell-mediated hypersensitivity reactions perpetuate it and induce chronic inflammatory, granulomatous, and fibrotic responses in the interstitium of the lungs.

Pulmonary lymphocyte recruitment: depletion of CD8+ T cells does not impair the pulmonary immune response to intratracheal antigen.

CD8+ T cells predominate in the lungs in hypersensitivity and human immunodeficiency virus-related lymphocytic pneumonitis, but their role in the immunopathogenesis of lung disease is unknown. We have shown that in immunized mice depleted of CD4+ T cells, CD8+ T cells are recruited into the lungs in response to intratracheal antigen challenge with sheep red blood cells (SRBC) (J. Clin.

Requirement of CD4-positive T cells for cellular recruitment to the lungs of mice in response to a particulate intratracheal antigen.

To determine whether CD4+ T cells participate in the recruitment of other lymphocyte subsets to the lungs, we examined pulmonary immune responses in C57BL/6 mice treated in vivo with the MAb GK1.5, either intact (which depletes CD4+ cells) or as F(ab')2 fragments (which block CD4 molecules). After intratracheal challenge with sheep erythrocytes, antigen-primed mice treated with intact GK1.

Inflammatory responses to Pneumocystis carinii in mice selectively depleted of helper T lymphocytes.

Pneumocystis carinii is the most important pulmonary pathogen in patients with the acquired immunodeficiency syndrome, but host defenses against P. carinii are not well characterized. We recently reported an experimental model of P.

Histologic analysis of an immune response in the lung parenchyma of mice. Angiopathy accompanies inflammatory cell influx.

To determine the histologic changes occurring during a pulmonary immune response, the lungs of antigen-primed C57BL/6 mice were examined on various days after intratracheal challenge with 10(8) sheep erythrocytes. The response was characterized by 1) dense perivascular aggregates composed largely of mononuclear cells; 2) endothelial cell hypertrophy and subendothelial inflammatory cell collections in vessels of a variety of sizes; 3) variable degrees of focal, reversible vascular injury (angiopathy) of both muscular arteries and small veins; and 4) increased cellularity of alveolar walls. Inflammatory cells appeared to emanate from small veins and venules and from minute thin-walled vessels adjacent to large arteries.

Characterization of bronchoalveolar lymphocytes during a specific antibody-forming cell response in the lungs of mice.

The goal of this study was to characterize the total numbers and phenotypes of lymphocyte subpopulations recovered by bronchoalveolar lavage during an experimental immune response in the lung parenchyma. Inbred mice (C57BL/6) were primed systemically and then challenged intratracheally with sheep red blood cells, a T-cell-dependent antigen. At various days later, we performed differential cell counts, measured the concentrations of specific antibody-forming cells, and determined lymphocyte phenotypes in bronchoalveolar lavage fluid by flow cytometry, distinguishing lymphocytes by light scatter parameters.

Expression of Ia by murine alveolar macrophages is upregulated during the evolution of a specific immune response in pulmonary parenchyma.

These studies were performed to test the hypothesis that the evolution of a specific immune response in lung parenchyma upregulates the expression of Ia on surface membranes of murine alveolar macrophages. A secondary antibody-forming cell response to sheep erythrocytes was generated in lung parenchyma by intratracheal antigen challenge of systemically primed mice. During the immune response, alveolar macrophages were retrieved by bronchoalveolar lavage, and the percentages and total numbers of Ia-positive macrophages were measured by indirect immunofluorescence.

The mechanism of appearance of specific antibody-forming cells in lungs of inbred mice after immunization with sheep erythrocytes intratracheally. II. Dose-dependence and kinetics of appearance of antibody-forming cells in hilar lymph nodes and lungs of unprimed and primed mice.

We are conducting studies designed to define the cellular basis for the appearance and accumulation of specific antibody-forming cells (AFC) in lung parenchyma of mice after intrapulmonary deposition of sheep erythrocytes (SRBC). This study was performed: to compare qualitatively the AFC responses to intratracheally administered antigen among unprimed mice and among mice primed either by adoptive transfer of sensitized lymphocytes or by systemic immunization, and to define quantitatively the relationship between the appearance of AFC in hilar lymph nodes (HLN) and in lung parenchyma in these 3 groups of mice. Both antigen dose-response and kinetic analyses of the appearance of AFC in the HLN and lung parenchyma were performed.

The capacity of normal murine alveolar macrophages to function as antigen-presenting cells for the initiation of primary antibody-forming cell responses to sheep erythrocytes in vitro.

The precise role of resident alveolar macrophages (AM) in the induction of immune responses to inhaled antigens is not known. In order to gain insight into the immune functions of AM in vivo, the present studies were performed to characterize several immune functional capacities of normal murine AM, to compare these with normal peritoneal macrophages (PM), and to determine the capacity of AM to serve as antigen-presenting cells for the induction of primary antibody-forming cell (AFC) responses to sheep erythrocytes (SRBC) in vitro. We compared the capacities of normal murine AM and of PM to: elaborate interleukin-1 (IL-1), express surface membrane Ia antigen, serve as accessory cells for mitogen-induced blastogenesis, and induce generation of primary AFC responses to SRBC in Mishell-Dutton cultures.

The distribution of procoagulant and plasminogen activator activities among density fractions of normal rabbit alveolar macrophages.

Rabbit alveolar macrophages can directly stimulate either coagulation or fibrinolysis by producing tissue thromboplastin and plasminogen activator activities, respectively. However, it is not known whether these 2 opposed physiologic activities are expressed by the same or different cells within a population of alveolar macrophages. This study was undertaken to determine the distribution of procoagulant and plasminogen activator activities among density-defined populations of rabbit alveolar macrophages.

Heterogeneity of immunologic function among subfractions of normal rat alveolar macrophages. II. Activation as a determinant of functional activity.

Previous studies have demonstrated differences in immunologic function among density-fractionated alveolar macrophages. The present study was undertaken to correlate these functional differences among alveolar macrophage density fractions with parameters of macrophage activation. Alveolar macrophages were lavaged from normal rats and separated into 5 density fractions by density gradient centrifugation.

The effect of pulmonary surface-active material on the generation and expression of murine B- and T-lymphocyte effector functions in vitro.

We demonstrated previously that surface-active material potently suppresses early proliferative responses of lymphocytes to a wide variety of immune stimuli in vitro. It is now evident that in vivo, effector B and T lymphocytes can be recruited into lung parenchyma subsequent to their generation in extrapulmonary lymphoid tissues. The purpose of the present study was to examine the effects of surface-active material on proliferation, differentiation, and expression of effector functions of cytotoxic T cells and antibody-forming B cells in vitro in order to gain insight into the potential immune regulatory role of surface-active material in vivo.

Heterogeneity of immunologic function among subfractions of normal rat alveolar macrophages.

Rat alveolar macrophages were examined for the presence of subpopulations with different capacities for modulation of mitogen-induced lymphocyte proliferation and production of the monokine, Interleukin-1 (IL-1). Alveolar macrophages lavaged from normal rats were separated into 5 density fractions by centrifugation through a continuous gradient of isosmotic colloidal silica (Percoll). Measurement of cell size and endogenous peroxidase suggested that the cells fractionated by density represented alveolar macrophages at different levels of cell maturation.

Prostaglandin E is required for the augmentation of procoagulant activity of LPS-stimulated rabbit alveolar macrophages.

We demonstrated previously that rabbit alveolar macrophages stimulated in vitro by bacterial lipopolysaccharide (LPS) have markedly enhanced procoagulant activity (PCA), caused by increased production of a cell-associated tissue thromboplastin. The present study examined the role of arachidonic acid metabolites in modulating the expression of this PCA. Alveolar macrophages lavaged from normal rabbits were incubated in vitro with LPS, indomethacin, and purified prostaglandins, and the resultant PCA was measured.

Procoagulant activity of rabbit alveolar macrophages.

Alveolar macrophages are thought to participate in the clearance of fibrin from the injured lung, but their ability to facilitate the conversion of fibrinogen to fibrin (procoagulant activity) has not been described. In order to characterize their procoagulant properties, unstimulated alveolar macrophages obtained from normal rabbits were tested for their ability to accelerate the coagulation of plasma in a one-stage clotting assay. Compared with control assays containing no macrophages (coagulation times greater than 500 s), intact cells (10(6)/ml) were shown to display procoagulant activity (coagulation time, 153.

The mechanism of appearance of specific antibody-forming cells in lungs of inbred mice after intratracheal immunization with sheep erythrocytes.

Immunization, ablation, and adoptive transfer studies were performed in inbred mice to define in vivo the cellular mechanisms for the appearance of specific antibody-forming cells (AFC) in pulmonary parenchyma. Mice were immunized locally or systemically with sheep erythrocytes (SRBC), and the concentrations of IgM- and IgG-producing AFC were measured in lung and extrapulmonary lymphoid tissues with a hemolytic-plaque assay. Splenectomized mice and recipients of adoptively transferred, sensitized lymphocytes were examined.

Immune functions of murine alveolar macrophages: binding of lymphocytes and support of lymphocyte proliferation.

Interactions between alveolar macrophages and lymphocytes may be important in the generation of pulmonary immune responses or in the induction of immunologic lung disease. We compared the relative abilities of normal murine alveolar macrophages and peritoneal macrophages to bind primed lymphocytes and to support antigen-induced lymphocyte proliferation. Alveolar macrophages were obtained by lung lavage and peritoneal macrophages by peritoneal lavage of normal mice.

Hyporesponsiveness of canine bronchoalveolar lymphocytes to mitogens: II. Analysis of macromolecular synthesis, T-cell antigen, and mitogen-binding.

Canine bronchoalveolar lymphocytes (BAL) and peripheral blood lymphocytes (PBL) were prepared by filtration over nylon wool columns and were studied for their ability to: (a) synthesize protein, RNA, and DNA after mitogen stimulation; (b) express T-cell antigen; and (c) bind radiolabeled mitogen. Bronchoalveolar lymphocytes were shown to be markedly hyporesponsive to mitogen stimulation as assessed by DNA synthesis after 72 hr of culture or by protein and RNA synthesis after 24 hr of culture. The hyporesponsiveness of BAL was not due to a decrease in the number of T-cells; results of an indirect immunofluorescent assay employing a rabbit antiserum indicated similar percentages of T-cells in BAL (78%) and PBL (79%).