Expression of the innate defense receptor S5D-SRCRB in the urogenital tract.

S5D-SRCRB is a novel mouse secretory glycoprotein belonging to the ancient and highly conserved scavenger receptor cysteine-rich superfamily of protein receptors. Available evidence indicates that S5D-SRCRB interacts with conserved microbial cell wall components, as well as with some endogenous proteins, and presents a restricted tissue expression pattern. This study further analyzes the expression of S5D-SRCRB along the mouse urogenital tract. Immunohistochemical staining for S5D-SRCRB was observed in spermatocytes from seminiferous tubules and in the epithelial surface from urethra and bladder, as well as in kidney tubules, mainly from medulla and papilla. Double stainings showed that S5D-SRCRB is expressed in both principal (P) and intercalated (IC) cells from renal collecting ducts (CD). By using an in vitro cell model of IC cell differentiation, preferential expression of S5D-SRCRB was observed in the apical border of terminally differentiated IC. Colocalization of S5D-SRCRB with galectin-3 (Gal-3) was also observed in kidney and bladder, but not in testis, supporting concurrent biochemical studies demonstrating the carbohydrate-dependent interaction of Gal-3 and S5D-SRCRB. Furthermore, upregulation of S5D-SRCRB expression was observed in in vitro and in vivo models of bacterial aggression, reinforcing the emerging view that CD, and specially IC, are important players in innate defense of the urinary tract against infection. Taken together, the results indicate that S5D-SRCRB is an integral component of the urogenital tract involved in innate immune functions.

Circadian rhythm and the influence of physical activity on circulating surfactant protein D in early and long-standing rheumatoid arthritis.

Surfactant protein D (SP-D) belongs to the collectin family and has pro-and anti-inflammatory capacities depending on its oligomerization. Previously, circulating SP-D was shown to be decreased in early rheumatoid arthritis (RA) and negatively correlated to disease activity. This study aimed at assessing the diurnal rhythmicity and the influence of physical activity on circulating SP-D in patients with RA at different stages compared with healthy individuals. Patients with early RA (ERA) with disease duration <6 months and with long-standing RA (LRA) with disease duration 5-15 years were included in two sub-studies. Healthy individuals served as controls. Diurnal variation: blood samples were collected every 3 h from 7 a.m to 10 p.m and the following morning. Physical activity: blood sampling was done before and after standardized physical challenge. SP-D was measured by ELISA. SP-D exhibited diurnal variation in healthy controls (n = 15) and in patients with ERA (n = 9) and LRA (n = 9) with peak values at 10 a.m. and nadir in the evening (controls: P < 0.001, ERA: P = 0.004 and LRA: P = 0.009). Three hours after cessation of physical activity, SP-D decreased below pre-exercise levels in both ERA (n = 10), LRA (n = 10) and controls (n = 13) (ERA: P < 0.001, LRA: P < 0.001 and controls: P = 0.005). In patients with RA, the decline was already observed 1 h post-exercise. Circulating SP-D exhibits diurnal variation both in patients with RA at different stages and in healthy controls. SP-D in serum decreases following physical activity in health and RA disease. This study underscores the need of standardized blood sampling conditions in future studies on SP-D.

Increasing antiviral activity of surfactant protein d trimers by introducing residues from bovine serum collectins: dissociation of mannan-binding and antiviral activity.

Collectins contribute to host defence through interactions with glycoconjugates on pathogen surfaces. We have prepared recombinant trimeric neck and carbohydrate recognition domains (NCRD) of collectins, and we now show that the NCRD of bovine conglutinin and CL-46 (like that of CL-43) have greater intrinsic antiviral activity for influenza A virus (IAV) than the human SP-D NCRD (hSP-D-NCRD). The three serum collectins differ from SP-D by having insertions adjacent to amino acid 325 and substitution of hydrophobic residues for arginine 343. We previously showed that a three amino acid (RAK) insertion, as found in CL-43, increases antiviral activity and mannan-binding activity of the hSP-D-NCRD, while the substitution of valine at 343, as in conglutinin, more strongly increased these activities. Mannan-binding activity of collectins has been considered to predict for ability to bind to high mannose glycans on viruses or other pathogens. We now show, however, that combined mutants containing the RAK insertion and R343V or R343I substitutions have greatly increased mannan-binding ability, but lower IAV binding or inhibiting activity than mutants containing R343V or R343I substitutions only. These findings indicate differences in the recognition of glycan structures of mannan and IAV by the NCRD and emphasize the importance of the flanking sequences in determining the differing interactions of human SP-D and bovine serum collectins with mannose-rich glycoconjugates on IAV and other pathogens. Of interest, we show conservation of some monoclonal antibody-binding epitopes between bovine collectin NCRD and hSP-D, suggesting shared structural motifs.

Elevated plasma surfactant protein D (SP-D) levels and a direct correlation with anti-severe acute respiratory syndrome coronavirus-specific IgG antibody in SARS patients.

Pulmonary SP-D is a defence lectin promoting clearance of viral infections. SP-D is recognized to bind the S protein of SARS-CoV and enhance phagocytosis. Moreover, systemic SP-D is widely used as a biomarker of alveolar integrity. We investigated the relation between plasma SP-D, SARS-type pneumonia and the SARS-specific IgG response. Sixteen patients with SARS, 19 patients with community-acquired pneumonia (CAP) (Streptococcus pneumonia) and 16 healthy control subjects were enrolled in the study. Plasma SP-D and anti-SARS-CoV N protein IgG were measured using ELISA. SP-D was significantly elevated in SARS-type pneumonia [median (95% CI), 453 (379-963) ng/ml versus controls 218 (160-362) ng/ml, P < 0.05] like in patients with CAP. SP-D significantly correlated with anti-SARS-CoV N protein IgG (r(2) = 0.5995, P = 0.02). The possible re-emergence of SARS or SARS-like infections suggests a need for minimal traumatic techniques for following the alveolar compartment, e.g. during testing of antivirals. We suggest that monitoring systemic SP-D may be useful in monitoring the alveolar integrity in SARS-type pneumonia. The significant correlation between plasma SP-D and anti-SARS-CoV-specific antibodies support the role for SP-D in interlinking innate and adaptive immune pathways.

Circulating surfactant protein D is decreased in early rheumatoid arthritis: a 1-year prospective study.

Innate immune system abnormalities, e.g., mannan-binding lectin (MBL) genotype variants, have been demonstrated to modify the disease course of rheumatoid arthritis (RA). Surfactant protein D (SP-D) shares important structural and functional properties with MBL suggesting that SP-D may be an additional RA disease modifier. The Met11Thr polymorphism in the N-terminal part of SP-D is an important determinant for the SP-D serum level, but this polymorphism is also essential to the function and assembly into oligomers. We aimed to compare the serum levels of SP-D in a cohort of newly diagnosed untreated RA patients with healthy matched controls, and to investigate if there was an association to core measures of disease activity within the first year after disease onset. Secondly, we aimed to investigate whether the Met11Thr polymorphism was associated with RA. Serum SP-D was significantly lower in DMARD naive RA patients compared with healthy controls (P = 0.016). Median SP-D concentration at inclusion was 878 ng/ml (95% CI: 730-1033) and 1164 ng/ml (95% CI: 1093-1366) in RA patients and matched controls, respectively. SP-D increased during Methotrexate treatment (P < 0.0001), and at 1-year follow-up median SP-D was 1032 ng/ml (95% CI: 777-1255). SP-D levels did not correlate with traditional disease activity measures. The Thr11/Thr11 genotype and the Thr11 allele tended to be more frequent in RA patients. In conclusion, the low serum level of SP-D and the lack of correlation with traditional disease activity measures indicate that SP-D reflects a distinctive aspect in the RA pathogenesis.

SALSA-A dance on a slippery floor with changing partners.

It is becoming increasingly clear that the connections between our immune system and the microbiota colonizing us have a tremendous impact on human health. A number of innate molecular defence mechanisms cooperate to selectively target unwanted microorganisms at the mucosal surfaces. Amongst others these include the complement system, IgA and the SALSA molecule. The salivary scavenger and agglutinin (SALSA), also known as deleted in malignant brain tumors 1 (DMBT1), salivary agglutinin (SAG) or gp340 is a multifunctional molecule with important functions in innate immunity, inflammation and epithelial homeostasis. The SALSA protein is expressed at most mucosal surfaces, where it is one of the most abundant proteins. In the fetal meconium and infant intestine it may constitute even up to 10% of the total protein amount. SALSA is found either directly associated with the epithelial surface or secreted into the lining fluids. In the fluid-phase SALSA interacts with a number of bacterial and viral organisms, as well as with endogenous ligands, including IgA, lactoferrin, surfactant proteins and complement components. While complement has been shown to impact the mucosal environment, this remains an area of limited research. The multiple interactions of the SALSA molecule provide a scaffold, where this potent defence system may engage in cooperative microbial clearance together with corresponding mucosal host ligands. With its high abundance, and multiple effects on both host and microbes, the SALSA molecule is a key player in maintaining the immunological balance at the mucosal surfaces. This is further supported by observations linking the expression of different SALSA isoforms to the development of chronic inflammatory conditions, such as Crohn's disease and ulcerative colitis. This review describes the latest advances in understanding functions of SALSA and its different isoforms. Recently recognized functions are related to complement activation and regulation, endothelial development and epithelial homeostasis. In addition, we suggest mechanisms how SALSA regulates inflammation at the mucosal surfaces.

Association between microfibrillar-associated protein 4 (MFAP4) and micro- and macrovascular complications in long-term type 1 diabetes mellitus.

AIMS: To evaluate microfibrillar-associated protein 4 (MFAP4) as a marker of micro- and macrovascular complications in patients with type 1 diabetes. METHODS: This cross-sectional study included 203 persons with a long duration of type 1 diabetes from a population-based cohort ascertained in the former Funen County, Denmark. Detection of plasma-MFAP4 (pMFAP4) was performed by the AlphaLISA Technique. Diabetic retinopathy (DR) was graded in accordance with the Early Treatment Diabetic Retinopathy Study adaptation of the modified Airlie House classification. A monofilament test was used to test for neuropathy, and nephropathy was evaluated in a single spot urine sample. Data describing macrovascular disease were obtained from the Danish National Patient Register. RESULTS: Median age and duration of diabetes were 58.7 and 43 years, respectively, and 61% were males. High levels of pMFAP4 were found in participants of old age, in women and in non-smokers (p < 0.05). In a multiple logistic regression model, patients with high levels of pMFAP4 were more likely to have diabetic neuropathy (OR 2.47 for quartile 4 versus quartile 1, 95% CI 1.01-6.03). No association was found between pMFAP4 and proliferative diabetic retinopathy, nephropathy or macrovascular disease. CONCLUSIONS: No association between pMFAP4 and macrovascular vascular complications was found. However, high levels of pMFAP4 correlated independently with diabetic neuropathy. Further studies on the predictive value of increased circulating MFAP4 in diabetic neuropathy are warranted.

DMBT1 encodes a protein involved in the immune defense and in epithelial differentiation and is highly unstable in cancer.

The gene deleted in malignant brain tumors 1 (DMBT1) has been proposed as a candidate tumor suppressor for brain, gastrointestinal, and lung cancer. It codes for a protein of unknown function belonging to the superfamily of scavenger receptor cysteine-rich proteins. We aimed at getting insights into the functions of DMBT1 by expression analyses and studies with a monoclonal antibody against the protein. The DMBT1 mRNA is expressed throughout the immune system, and Western blot studies demonstrated that isoforms of DMBT1 are identical to the collectin-binding protein gp-340, a glycoprotein that is involved in the respiratory immune defense. Immunohistochemical analyses revealed that DMBT1 is produced by both tumor-associated macrophages and tumor cells and that it is deregulated in glioblastoma multiforme in comparison to normal brain tissue. Our data further suggest that the proteins CRP-ductin and hensin, both of which have been implicated in epithelial differentiation, are the DMBT1 orthologs in mice and rabbits, respectively. These findings and the spatial and temporal distribution of DMBT1 in fetal and adult epithelia suggest that DMBT1 further plays a role in epithelial development. Rearrangements of DMBT1 were found in 16 of 18 tumor cell lines, and hemizygous deletions were observed in a subset of normal individuals, indicating that the alterations in tumors may be a result of both pre-existing deletions uncovered by a loss of heterozygosity and secondary changes acquired during tumorigenesis. Thus, DMBT1 is a gene that is highly unstable in cancer and encodes for a protein with at least two different functions, one in the immune defense and a second one in epithelial differentiation.

Deleted in Malignant Brain Tumors 1 is a versatile mucin-like molecule likely to play a differential role in digestive tract cancer.

Deleted in Malignant Brain Tumors 1 (DMBT1) has been proposed as a candidate tumor suppressor gene for brain, lung, and digestive tract cancer. In particular, alterations of the gene and/or a loss of expression have been observed in gastric, colorectal, and esophageal carcinomas. Initial evidence has accumulated that DMBT1 may represent a multifunctional protein. Because the consequences of a loss of DMBT1 function may be different depending on its original function in a particular tissue, we wondered if it is appropriate to assume a uniform role for DMBT1 in digestive tract carcinomas. We hypothesized that a systematic characterization of DMBT1 in the human alimentary tract would be useful to improve the understanding of this molecule and its role in digestive tract carcinomas. Our data indicate that the expression pattern and subcellular distribution of DMBT1 in the human alimentary tract is reminiscent of epithelial mucins. Bovine gallbladder mucin is identified as the DMBT1 homologue in cattle. An elaborate alternative splicing may generate a great variety of DMBT1 isoforms. Monolayered epithelia display transcripts of 6 kb and larger, and generally show a lumenal secretion of DMBT1 indicating a role in mucosal protection. The esophagus is the only tissue displaying an additional smaller transcript of approximately 5 kb. The stratified squamous epithelium of the esophagus is the only epithelium showing a constitutive targeting of DMBT1 to the extracellular matrix (ECM) suggestive of a role in epithelial differentiation. Squamous cell carcinomas of the esophagus show an early loss of DMBT1 expression. In contrast, adenocarcinomas of the esophagus commonly maintain higher DMBT1 expression levels. However, presumably subsequent to a transition from the lumenal secretion to a targeting to the ECM, a loss of DMBT1 expression also takes place in adenocarcinomas. Regarding DMBT1 as a mucin-like molecule is a new perspective that is instructive for its functions and its role in cancer. We conclude that DMBT1 is likely to play a differential role in the genesis of digestive tract carcinomas. However, although DMBT1 originally has divergent functions in monolayered and multilayered epithelia, carcinogenesis possibly converges in a common pathway that requires an inactivation of its functions in the ECM.

The genomic structure of the DMBT1 gene: evidence for a region with susceptibility to genomic instability.

Increasing evidence has accumulated for an involvement of the inactivation of tumour suppressor genes at chromosome 10q in the carcinogenesis of brain tumours, melanomas, and carcinomas of the lung, the prostate, the pancreas, and the endometrium. The gene DMBT1 (Deleted in Malignant Brain Tumours 1) is located at chromosome 10q25.3-q26.1, within one of the putative intervals for tumour suppressor genes. DMBT1 is a member of the scavenger-receptor cysteine-rich (SRCR) superfamily and displays homozygous deletions or lack of expression in glioblastoma multiforme, medulloblastoma, and in gastrointestinal and lung cancers. Based on these properties, DMBT1 has been proposed to be a candidate tumour suppressor gene. We have determined the genomic sequence of DMBT1 to allow analyses of mutations. The gene has at least 54 exons that span a genomic region of about 80 kb. We have identified a putative exon with coding potential for a transmembrane domain. Our data further suggest that alternative splicing gives rise to isoforms of DMBT1 with a differential utilization of SRCR domains and SRCR interspersed domains. The major part of the gene harbours locus specific repeats. These repeats may point to the DMBT1 locus as a region susceptible to chromosomal instability.

Structural characterisation of human proteinosis surfactant protein A.

Human surfactant protein-A (SP-A) has been purified from a proteinosis patient and characterised by a combination of automated Edman degradation and mass spectrometry. The complete protein sequence was characterised. The major part of SP-A was shown to consist of SP-A2 gene product, and only a small amount of SP-A1 gene product was shown to be present. A cysteine extension to the N-terminal was indicated by sequence data, but was not definitely proven. All proline residues in the Y position of Gly-X-Y in the collagen-like region were at least partially modified to hydroxy-proline, but no lysine residues were found to be modified. A complex N-linked glycosylation was found on Asn-187 showing great heterogeneity as variants from a mono-antennary to penta-antennary glycosylation with varying amounts of attached pentose were identified. The disulfide bridges in the carbohydrate recognition domain were identified to be in the 1-4, 2-3 pattern common for collectins. Interchain disulfide bridges were discovered between two Cys-48 residues and cysteine residues in the N-terminal region. However, the exact disulfide bridge connections within the bouquet-like ultrastructure could not be established.

Lung surfactant proteins (SP-A and SP-D) in non-adaptive host responses to infection.

The lung surfactant proteins A and D (SP-A and SP-D) are collectins composed of C-type lectin domains attached to collagen regions. SP-A and SP-D are mainly found in the surfactant covering the pulmonary epithelial cells, but are also produced by cells lining the gastrointestinal tract. The main role of SP-A and SP-D is to interact directly with carbohydrate on the surface of microbial pathogens, thereby initiating a variety of effector mechanisms. This review focuses on the non-adaptive host responses of SP-A and SP-D to infection. Interaction of SP-A and SP-D with phagocytes is discussed and the structure and function of the putative receptors for SP-A and SP-D is presented. SP-A and SP-D seem to be regulated in a way similar to acute-phase proteins in the course of inflammation and evidence for the involvement of SP-A and SP-D as immunomodulators as well as their role in clearing allergens and modulating effector mechanisms in allergic reactions is discussed.

Affinity and kinetic analysis of the bovine plasma C-type lectin collectin-43 (CL-43) interacting with mannan.

Collectins are C-type lectins which have been implied to play an important role in the innate immune defence against microorganisms. The critical discriminatory event in the opsonization of microorganisms by collectins is the interaction of the C-type lectin domain with microbial carbohydrates. Surface plasmon resonance measurements allow for quantitative real-time measurements of binding interaction between immobilized carbohydrate and unlabelled lectin in solution. Binding analysis were carried out with purified collectin-43 (CL-43) which structurally is the simplest collectin consisting of only three polypeptides each terminating in a C-type lectin domain. The target was immobilized yeast mannan. The molecular mass of native CL-43 was determinated by mass spectroscopy to 99.8 kDa. The dissociation rate (kdiss) of the C-type lectin-carbohydrate binding was fast (1.19-1.36 x 10(-2) second-1), and the association rate (kass) was 4.37-5.07 x 10(5) M-1 second-1. The equilibrium constant for dissociation (Kd) was 2.68-2.72 x 10(-8) M.

Calcium-dependent and calcium-independent signals in the conglutinin-binding assay (KgBa) for immune complexes. Influence of anti-collagen-antibodies.

A solid phase ELISA conglutinin-binding assay (KgBa) was evaluated for the detection of circulating immune complexes. ELISA wells were coated with purified bovine conglutinin and incubated with test sera. Bound IgG was detected with enzyme labelled anti-immunoglobulin. Heat aggregated IgG which had been "solubilized" (i.e., complement treated by incubation with serum) was employed as a reference. The binding of the complement-reacted IgG to solid phase conglutinin was found to be calcium-dependent and inhibitable with N-acetyl-D-glucosamine (GlcNAc). Prolonged incubation (4 days) of aggregated IgG with serum at 37 degrees C abolished the binding to conglutinin, a finding consistent with the complete degradation of deposited C3b to C3c and C3d. The solubilized IgG that bound to solid phase conglutinin was found by gel chromatography to be of high molecular weight (greater than 600 kDa). Binding of IgG to solid phase bovine conglutinin was also observed to a variable degree in normal and pathological sera. However, in this situation the IgG binding was largely calcium-independent, was not inhibited by GlcNAc and did not decrease after prolonged incubation of the serum at 37 degrees C. The reactive IgG eluted on gel chromatography at the position of monomeric IgG suggesting binding via the antigen binding sites. Binding of this IgG was inhibited by both collagen type II and purified conglutinin. These observations suggest that the assay detects cross-reacting autoantibodies against collagen epitopes, or, alternatively, antibodies against the dietary antigen, bovine conglutinin.

Difference and ratio plots: simple tools for improved presentation and interpretation of scientific data. Unexpected possibilities for the use of the conglutinin binding assay in inflammatory rheumatic diseases.

11111onglutinin-binding assay (KgBa) has gained widespread use for the detection of circulating immune complexes. A recent paper questioned the interpretation of the results obtained by this method and the validity of the assay (Holmskov et al. (1992) J. Immunol. Methods 148, 225). We now present hitherto unnoted differences between controls and patients with either rheumatoid arthritis or systemic lupus erythematosus. For this we use simple, but unconventional, graphic representations of the data, based on difference plots and ratio plots. Differences between patients with Burkitt's lymphoma and systemic lupus erythematosus from another previously published study (Macanovic, M. and Lachmann, P.J. (1979) Clin. Exp. Immunol. 38, 274) are also represented using ratio plots. Our observations indicate that analysis by regression analysis may often be misleading.

A time-resolved immunofluorometric assay for quantification of collectin-43.

CL-43 is a serum collectin involved in the innate immunity of cattle and variability of serum CL-43 may relate to disease in cows. A high capacity time-resolved immunofluorometric assay (TRIFMA) for the bovine collectin-43 (CL-43) was developed. The TRIFMA was constructed as a noncompetitive sandwich based on polyclonal antibodies and a novel monoclonal antibody (mab) raised against CL-43 and was set up to run on an automatic analyser designed for the TRIFMA detection system. The polyclonal antibodies were immobilized on microtiter plate wells and incubated with diluted plasma samples, including quality controls (QC) and dilutions of a plasma with known CL-43 concentration. CL-43 was sandwiched between the capture antibodies and the monoclonal antibody and the detection was optimised with biotin-labelled secondary antibodies and streptavidin-Eu3+. Plates were washed four times between each step and finally incubated with enhancement solution before measuring the fluorescence. The assay detection limit was 0.24 ng/ml and the working range was 0.54-22 ng/ml. Recovery was 92.3% when samples were spiked with 2.0 ng/ml of CL-43. Intraplate and interplate coefficients of variation were in the range of 1.11-2.36% and 0.70-1.35%, respectively. No circadian rhythm (24-h variation) in CL-43 plasma levels was observed, indicating that plasma levels were not influenced by e.g. feeding. Samples could be stored at -20 degrees C and were not sensitive to repeated freezing and thawing. In conclusion, the developed TRIFMA for CL-43 is specific and reliable over a measurement range covering most situations.

A time-resolved immunofluorometric assay for quantification of the bovine collectin conglutinin.

A high capacity time-resolved immunofluorometric assay (TRIFMA) for the bovine collectin conglutinin was developed. The TRIFMA was constructed as a non-competitive sandwich assay based on polyclonal antibodies as the capture reagent and a novel monoclonal antibody raised against conglutinin as the detection reagent and was set up to run on an automatic analyzer designed for the TRIFMA detection system. Polyclonal antibodies immobilized on microtiter plate wells were incubated overnight at 4 degrees C with diluted plasma samples, including quality controls (QC) and dilutions of a plasma with known conglutinin concentration. Conglutinin was sandwiched between the capture antibodies and the monoclonal antibody and the detection optimised with biotin-labelled secondary antibodies and streptavidin-Eu(3+). Plates were washed four times between each step and finally incubated with enhancement solution before measuring the fluorescence. The assay detection limit was 0.34 ng/ml and the working range 0.80 ng/ml-0.20 microg/ml. Intra-plate and inter-plate coefficients of variation (CV) were in the range of 5.0-8.3% and 6.2-7.2%, respectively, at concentrations of 3.4 and 150 ng/ml. Recovery was 90.9+/-2.4% and 98.8+/-2.5% when samples were spiked with 20 ng/ml and 100 ng/ml purified bovine conglutinin (BK). No circadian rhythm (24-h variation) in conglutinin plasma levels was observed across animals, indicating that the plasma levels were not influenced by, e.g. feeding. Samples could be stored at -20 degrees Celsius and were not sensitive to repeated freezing and thawing. In conclusion, the developed TRIFMA for bovine conglutinin is specific and reliable over a measurement range covering most situations.

Structural aspects of collectins and receptors for collectins.

The collectins are oligomeric molecules composed of C-type lectin domains attached to collagen regions via alpha-coiled neck regions. Five members of the collectins have been characterized. Mannan-binding lectin (MBL), conglutinin and collectin-43 (CL-43) are serum proteins produced by the liver. Lung surfactant protein A (SP-A) and lung surfactant protein D (SP-D) are mainly found in the lung, where they are synthesized by alveolar type II cells and secreted to the alveolar surface. The collectins are believed to play an important role in innate immunity. They bind oligosaccharides on the surface of a variety of microbial pathogens. After binding of the collectins to the microbial surface effector mechanisms such as agglutination, neutralizing or opsonization of the microorganisms for phagocytosis are initiated. SP-A and SP-D stimulate chemotaxis of phagocytes and once bound to the phagocytes, the production of oxygen radicals can be induced. In the case of MBL the opsonization can be further enhanced by complement activation via the MBLectin pathway while conglutinin interacts with the complement system by binding to the complement degradation product iC3b. A number of receptors and binding molecules interacting with the collectins are found on the membrane or in association with the membrane of various cells responsible for phagocytosis and clearance of microorganisms. This paper focus on the structural aspects of the collectins and the receptors for collectins.

Immune complex binding to erythrocyte-CR1 (CD 35), CR1 expression and levels of erythrocyte-fixed C3 fragments in SLE outpatients.

Erythrocytes (E) from a cross-sectional group of 22 outpatients with systemic lupus erythematosus (SLE) and/or mixed connective tissue disease (MCTD), the majority without active disease (n = 14), were analyzed for CR1 antigen expression and capacity to bind complement opsonized, radiolabelled immune complexes (IC). Furthermore, E-bound C3 fragments and the plasma C3d concentration were determined. E-bound C3b/iC3b fragments were not elevated in patients with SLE, whereas E from 11 out of 22 SLE patients had increased C3d levels which correlated with the plasma C3d concentration (Rs 0.73, p less than 0.001). E-fixed C3d fragments did not affect the binding of Mab or preopsonized IC to E-CR1 and were not correlated with disease activity or medical treatment. Antigen expression of E-CR1 measured by ELISA or agglutination showed positive correlation with the IC binding capacity of E-CR1 (Rs 0.92 and 0.72 respectively, p less than 001). The IC binding capacity of E-CR1 from SLE patients was significantly reduced (p less than 0.005), whereas the antigen expression of CR1 (ELISA) on E from the patients did not differ from that of E from healthy donors (p greater than 0.1). E-CR1 antigen was measured by Mab reacting with an epitope outside the IC-binding site of E-CR1. E-CR1 antigen expression or IC binding showed no correlation either with disease activity or prednisolone treatment. However, 4 og 5 patients with MCTD and 4 of 5 patients receiving Imurel were found to have low E-CR1 expression and capacity to bind IC. Thus, measurement of antigenic E-CR1 in a cross-sectional group of SLE outpatients by use of Mab reacting with an epitope outside the ligand-binding region of CR1 did not reveal a significantly reduced CR1 expression. However, an assay for CR1-mediated IC binding showed a clearly reduced E-CR1 function.

Immunohistochemical detection of salivary agglutinin/gp-340 in human parotid, submandibular, and labial salivary glands.

Salivary agglutinin is a Streptococcus mutans binding protein and a member of the scavenger receptor cysteine-rich superfamily. It is identical to lung gp-340 and brain DMBT1, which possibly play a role in innate immunity and tumor suppression, respectively. The goal of this study was to localize salivary agglutinin in human salivary glands. Two monoclonal antibodies, directed against gp-340, were characterized. mAb 213-1 reacted with sialic acid epitopes and cross-reacted with MUC7. The reaction with mAb 213-6 disappeared after reduction, suggesting that a protein epitope was recognized. In the parotid gland, immunohistochemical labeling with mAb 213-6 was found in the duct cells. In the submandibular gland and labial gland, both serous acini and demilune cells were labeled. In the labial gland, labeling was found at the luminal side of the duct cells. Salivary agglutinin was distinctly localized in salivary glands, but in distinct glandular secretions, no differences in electrophoretic behavior were observed.