Epithelia from many tissues express protease-activated receptors (PARs) that play a major role in several different physiological processes. In this study, we examined their capacity to modulate IL-6, IL-8, and PGE2 production in both the A459 and BEAS-2B cell lines and primary human bronchial epithelial cells (HBECs). All three cell types expressed PAR-1, PAR-2, PAR-3, and PAR-4, as judged by RT-PCR and immunocytochemistry. Agonist peptides corresponding to the nascent N termini of PAR-1, PAR-2, and PAR-4 induced the release of cytokines from A549, BEAS-2B, and HBECs with a rank order of potency of PAR-2 > PAR-4 > PAR-1 at 400 μM. PAR-1, PAR-2, and PAR-4 also caused the release of PGE2 from A549 and HBECs. The PAR-3 agonist peptide was inactive in all systems tested. PAR-1, PAR-2, or PAR-4, in combination, caused additive IL-6 release, but only the PAR-1 and PAR-2 combination resulted in an additive IL-8 response. PAR peptide-induced responses were accompanied by changes in intracellular calcium ion concentrations. However, Ca2+ ion shutoff was ∼2-fold slower with PAR-4 than with PAR-1 or PAR-2, suggesting differential G protein coupling. Combined, these data suggest an important role for PAR in the modulation of inflammation in the lung.

SummaryImmunohistochemical analysis of challenge sites such as skin and the peritoneal cavity has identified neutrophils as virtually the sole cellular participants in acute bacterial inflammation, peak influx occurring 24-48 h in advance of mononuclear cell populations associated with adaptive immunity This study challenges the general applicability of this paradigm. We demonstrate here that the earliest detectable cellular response after inhalation ofMoraxdla catarrhalis organisms is the recruitment of putative class II major histocompatibflity complex-bearing dendritic cell (DC) precursors into the airway epithelium, the initial wave arriving in advance of the neutrophil influx. Unlike the neutrophils which rapidly transit into the airway lumen, the DC precursors remain within the epithelium during the acute inflammatory response where they differentiate, and develop the dendriform morphology typical of resident DC found in the normal epithelium. During the ensuing 48-h period, these cells then migrate to the regional lymph nodes. No comparable DC response was observed after epidermal or intraperitoneal challenge, and it may be that mucosal surfaces are unique in their requirement for rapid DC responses during acute inflammation. We hypothesize that the role of the DC influx during acute inflammation may be surveiUance for opportunistic viruses, and that this covert protective mechanism is operative at a restricted number of mucosal tissue sites. p revious reports from this laboratory have established the importance of dendritic cells (DC) as APC within normal lung tissue (1, 2), and have additionally shown that a functionally and morphologically identical DC population exists within the epithelial lining of the conducting airways of both humans (3) and rodents (4, 5), where they form a contiguous network analogous to the Langerhans cell (LC) population in the epidermis.We have also recently presented evidence that the density, distribution, and surface phenotype of airway DC populations reflects the level of stimulation provided by inhalation of airborne irritant stimuli (5). Moreover, brief exposure to aerosolized bacterial LPS was demonstrated to induce a transient increase (,o50%) in the density of airway intraepithelial DC during the 24-48-h period after exposure, suggesting active participation of DC in the acute inflammatory response (5). The present study sought to further elucidate the role of DC in acute inflammation in the airways, employing a much more potent inhaled stimulus in the form of whole bacteria. Materiah and MethodsAnimals. Specific pathogen-free (SPF) adult PVG rats were used in these experiments. They were barrier housed under dust-free conditions, as detailed previously (5).Aerosol Exposure The animals were exposed for 60 rain to an aerosol of heat-killed MoraxeUa catarrhalis organisms (clinical hospital isohte) suspended in normal saline at '~109 CFU/ml.Antibodies and Iraraunostaining. The mAbs Ox6 (Ia), Ox19 (CDS; pan T cell), Ox12 (r light chains; pan B cell) (6), and Ox 42 (~ cha...

A key rate-limiting step in the adaptive immune response at peripheral challenge sites is the transmission of antigen signals to T cells in regional lymph nodes. Recent evidence suggests that specialized dendritic cells (DC) fulfill this surveillance function in the resting state, but their relatively slow turnover in most peripheral tissues brings into question their effectiveness in signaling the arrival of highly pathogenic sources of antigen which require immediate mobilization of the full range of host defenses for maintenance of homeostasis. However, the present report demonstrates that recruitment of a wave of DC into the respiratory tract mucosa is a universal feature of the acute cellular response to local challenge with bacterial, viral, and soluble protein antigens. Consistent with this finding, we also demonstrate that freshly isolated respiratory mucosal DC respond in vitro to a variety of CC chemokines as well as complementary cleavage products and N-formyl-methionyl-leucine-phenylalanine. This suggests that rapid amplification of specific antigen surveillance at peripheral challenge sites is an integral feature of the innate immune response at mucosal surfaces, and serves as an “early warning system” to alert the adaptive immune system to incoming pathogens.

Sialoadhesin is a macrophage‐restricted adhesion molecule of 185 kDa that mediates sialic acid‐dependent binding to cells. It is expressed strongly by macrophages in lymphoid and haemopoietic tissues where it is likely to mediate cell‐cell interactions. Here we report the molecular cloning of murine sialoadhesin and show that it is a new member of the immunoglobulin (Ig) superfamily with 17 Ig‐like domains. COS cells transfected with a cDNA encoding full‐length sialoadhesin bound mouse bone marrow cells in a sialic acid‐dependent manner. Alternatively spliced cDNAs, predicting soluble forms of sialoadhesin containing the first three or 16 Ig‐like domains of sialoadhesin, were expressed in COS cells and the respective proteins purified. When immobilized on plastic, the 16‐domain form bound cells in a sialic acid‐dependent manner, suggesting that sialoadhesin can function in both secreted and membrane‐bound forms. The most similar proteins in the database were CD22, myelin‐associated glycoprotein, Schwann cell myelin protein and CD33. Like sialoadhesin, CD22 mediates sialic acid‐dependent cell adhesion. The sequence similarity of sialoadhesin to CD22 and related members of the Ig superfamily indicates the existence of a novel family of sialic acid binding proteins involved in cell‐cell interactions.

Macrophage subpopulations in the mouse express a lectin‐like receptor, sialoadhesin (originally named sheep erythrocyte receptor, SER), which selectively recognizes sialoglycoconjugates and is likely to be involved in cellular interactions of stromal macrophages in haematopoietic and lymphoid tissues. In this report we describe the purification and ligand specificity of sialoadhesin isolated from mouse spleen. Purified sialoadhesin, a glycoprotein of 185 kd apparent Mr, agglutinated sheep or human erythrocytes at nanomolar concentrations in a sialic acid‐dependent manner. Low angle shadowing and electron microscopy showed that sialoadhesin consisted of a globular head region of approximately 9 nm and an extended tail of approximately 35 nm. To investigate the specificity for sialic acid, we studied the interaction of sialoadhesin with derivatized human erythrocytes, glycoproteins, and glycolipids. In conclusion, sialoadhesin specifically recognizes the oligosaccharide sequence Neu5Ac alpha 2‐‐‐‐3Gal beta 1‐‐‐‐3GalNAc in either sialoglycoproteins or gangliosides. These findings imply that specific sialoglycoconjugates carrying this structure may be involved in cellular interactions between stromal macrophages and subpopulations of haematopoietic cells and lymphocytes.