Expression Of Complement Receptors Research Articles

Complement receptor 2 is up regulated in the spinal cord following nerve root injury and modulates the spinal cord response.

BackgroundActivation of the complement system has been implicated in both acute and chronic states of neurodegeneration. However, a detailed understanding of this complex network of interacting components is still lacking.MethodsLarge-scale global expression profiling in a rat F2(DAxPVG) intercross identified a strong cis-regulatory influence on the local expression of complement receptor 2 (Cr2) in the spinal cord after ventral root avulsion (VRA). Expression of Cr2 in the spinal cord was studied in a separate cohort of DA and PVG rats at different time-points after VRA, and also following sciatic nerve transection (SNT) in the same strains. Consequently, Cr2−/− mice and Wt controls were used to further explore the role of Cr2 in the spinal cord following SNT. The in vivo experiments were complemented by astrocyte and microglia cell cultures.ResultsExpression of Cr2 in naïve spinal cord was low but strongly up regulated at 5–7 days after both VRA and SNT. Levels of Cr2 expression, as well as astrocyte activation, was higher in PVG rats than DA rats following both VRA and SNT. Subsequent in vitro studies proposed astrocytes as the main source of Cr2 expression. A functional role for Cr2 is suggested by the finding that transgenic mice lacking Cr2 displayed increased loss of synaptic nerve terminals following nerve injury. We also detected increased levels of soluble CR2 (sCR2) in the cerebrospinal fluid of rats following VRA.ConclusionsThese results demonstrate that local expression of Cr2 in the central nervous system is part of the axotomy reaction and is suggested to modulate subsequent complement mediated effects.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-015-0413-6) contains supplementary material, which is available to authorized users.

Abstract A08: Distribution, cutoff, and functional significance of a potential biomarker for Imprime PGG, an experimental cancer immunotherapeutic, in a healthy subject population

Abstract Imprime PGG (Imprime) is a yeast-derived beta-1,3/1,6 glucan that binds complement receptor 3 (CR3) on innate immune cells and enables these cells to exert anti-tumor activity against tumor cells that have been opsonized by iC3b following targeting by anti-tumor antibodies. Following incubation with whole blood (WB) from healthy subjects, Imprime was shown to bind to neutrophils and monocytes via CR3 and modulate complement receptor expression, activation marker expression, and interleukin-8 (IL-8) production. These effects, however, differed widely among subjects. It was subsequently observed that Imprime-induced functional activities occurred predominantly in individuals with higher levels of endogenous immunoglobulin G (IgG) or IgM anti-beta-glucan antibodies (ABA) and that ABA are a prerequisite for opsonizing Imprime to allow its binding to CR3. A small pilot study (n=32) with healthy subjects using prototype enzyme-linked immunosorbent assays (ELISAs) to measure IgG and IgM ABA suggested correlations between ABA levels, Imprime binding to neutrophils in WB, and consequent induction of functional responses. The objectives of this study were to further optimize and qualify the prototype ELISAs and, in a larger cohort of healthy subjects (n=143), to confirm the significance of elevated ABA levels with respect to binding of Imprime to neutrophils and monocytes and Imprime–induced functional changes. Qualification of the IgG and IgM ABA ELISAs yielded good inter-assay precision (coefficients of variation <10%), linearity (recovery 97-112%), and dynamic range (2.5 logs). Incubation of WB samples with Imprime resulted in high binding to neutrophils (>5% of cells) in samples from 52% of the subjects. Samples from these same subjects also exhibited high Imprime binding to monocytes. ABA levels in the high binding individuals were significantly greater than those in the low binding individuals (p<0.0001 for IgG and p=0.01 for IgM). IgG ABA levels were more highly correlated with Imprime binding to neutrophils and monocytes (r=0.64 and r=0.61, respectively) than IgM ABA levels (r=0.22 and r=0.33, respectively). There was no correlation of ABA levels with age, gender, or total serum immunoglobulin concentration. Receiver operator characteristic (ROC) curve analysis comparing sensitivity and specificity of ABA levels vs. Imprime binding to neutrophils yielded an area under the curve (AUC) of 0.89 for IgG and 0.70 for IgM and generated several options for cutoffs. At one proposed ABA cutoff set at 95% specificity for binding, 36% of subjects had IgG ABA levels ≥ the cutoff, 20% had IgM ABA levels ≥ the cutoff, and 46% had levels ≥ either cutoff. The sensitivity to detect high Imprime binding to neutrophils was 64% for IgG and 33% for IgM, with a combined sensitivity of 80%. Similar correlations were seen with Imprime binding to monocytes. In subsets of the healthy population in which functional evaluations were also performed following in vitro exposure to Imprime, IgG ABA levels at or above vs. below the cutoff correlated with higher C4a (n=32; p=0.0003), C5a (n=32; p<0.0001), and SC5b-9 (n=32; p<0.0001) production, increased production of IL-8 (n=129; p<0.0001), and increased neutrophil and monocyte CR3 expression (n=40; p=0.006 and n=37; p=0.009 respectively). Data presented here, using the further optimized ELISAs for measurement of IgG and IgM ABA in WB samples from a larger healthy population, confirm that serum ABA levels correlate with in vitro neutrophil as well as monocyte binding and response to Imprime. Furthermore, ABA cutoffs at high specificity could identify the majority of healthy individuals whose cells demonstrated this response. The use of ABA as a clinical biomarker for Imprime response in cancer patients is under investigation. Citation Format: Diane McMurray, Ben Harrison, Katie Ertelt, Richard Walsh, Lindsay Wurst, Steven Leonardo, Nadine Ottoson, Adria Bykowski Jonas, Xiaohong Qiu, Nandita Bose, Peter Maimonis. Distribution, cutoff, and functional significance of a potential biomarker for Imprime PGG, an experimental cancer immunotherapeutic, in a healthy subject population. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr A08.

Tobacco and e-cigarette products initiate Kupffer cell inflammatory responses.

Kupffer cells are liver resident macrophages that are responsible for screening and clearing blood of pathogens and foreign particles. It has recently been shown that Kupffer cells interact with platelets, through an adhesion based mechanism, to aid in pathogen clearance and then these platelets re-enter the general systemic circulation. Thus, a mechanism has been identified that relates liver inflammation to possible changes in the systemic circulation. However, the role that Kupffer cells play in cardiovascular disease initiation/progression has not been elucidated. Thus, our objective was to determine whether or not Kupffer cells are responsive to a classical cardiovascular risk factor and if these changes can be transmitted into the general systemic circulation. If Kupffer cells initiate inflammatory responses after exposure to classical cardiovascular risk factors, then this provides a potential alternative/synergistic pathway for cardiovascular disease initiation. We aimed to elucidate the prevalence of this potential pathway. We hypothesized that Kupffer cells would initiate a robust inflammatory response after exposure to tobacco cigarette or e-cigarette products and that the inflammatory response would have the potential to antagonize other salient cells for cardiovascular disease progression. To test this, Kupffer cells were incubated with tobacco smoke extracts, e-cigarette vapor extracts or pure nicotine. Complement deposition onto Kupffer cells, Kupffer cell complement receptor expression, oxidative stress production, cytokine release and viability and density were assessed after the exposure. We observed a robust inflammatory response, oxidative stress production and cytokine release after Kupffer cells were exposed to tobacco or e-cigarette extracts. We also observed a marginal decrease in cell viability coupled with a significant decrease in cell density. In general, this was not a function of the extract formulation (e.g. tobacco vs. e-cigarette products or the formulation of the cigarette product). These results indicate that Kupffer cells are responsive to classical cardiovascular risk factors and that an inflammatory response is initiated that may pass into the general systemic circulation.

Abstract 447: β-cyclodextrin Reduces Cholesterol Crystal-induced Inflammation Through Modulating Complement Activation

Atherosclerosis is an inflammatory condition and the underlying cause for cardiovascular disease. Cholesterol crystals (CC) are found to be abundant in atherosclerotic plaques and we have previously shown that CC initiate an inflammatory response via the complement system and inflammasome activation. Cyclic oligosaccharide 2-hydroxypropyl-β-cyclodextrin (BCD) is a compound that solubilizes lipophilic substances and is commonly used in pharmaceuticals or drug delivery. BCD is reported to increase cholesterol solubility and to promote the removal of cholesterol from foam cells. However, it remains unknown whether BCD has any effect on crystalline cholesterol. We here show that BCD attenuates the CC -induced inflammatory cytokine response as well as regulates a range of CC-related genes in human peripheral blood mononuclear cells. BCD binds to CC and prevents deposition of complement factors on CC in human plasma. Furthermore, BCD also decreases the formation of soluble terminal complement complex (TCC) and the expression of complement receptor 3 in response to CC stimulation in human whole blood. Induction of TCC by mono sodium urate crystals or zymosan was not affected by BCD. Of interest, after 1 hr of incubation, BCD is starting to dissolve the CC. These data demonstrate that BCD is a strong inhibitor of CC-induced inflammation, which might be explained by BCD-mediated attenuation of complement activation. These data suggest that BCD is a potential candidate for treatment of atherosclerosis.

Inhibitory Effects of Areca Nut Extract on Expression of Complement Receptors and Fc Receptors in Human Neutrophils

Chewing of areca quid increases the prevalence of periodontal diseases. Areca nut extract (ANE) inhibits the phagocytic activity of human neutrophils. This in vitro study investigates the effects of ANE on complement- and antibody-opsonized phagocytosis by neutrophils. Expression of complement receptors, Fc receptors, and F-actin in ANE-treated neutrophils is also analyzed. The viability of ANE-treated neutrophils was determined using the propidium iodide staining method. The possible effects of ANE on the expression of complement receptors and Fc receptors were examined using an immunofluorescence staining method followed by flow cytometry and confocal laser scanning microscopy. The phagocytic activity of neutrophils against complement or immunoglobulin (Ig)G-opsonized fluorescent beads was analyzed using flow cytometry. Expression of F-actin was determined using confocal laser scanning microscopy. ANE significantly inhibited the production of complement receptors (CR1, CR3, and CR4) and Fc receptors (FcγRII and FcγRIII) in a concentration-dependent manner. Treatment of neutrophils with ANE significantly impaired their ability to phagocytose fluorescent beads. ANE also inhibited phagocytosis of fluorescent beads that were opsonized by complement or IgG. Moreover, expression of F-actin was inhibited after ANE treatment. ANE inhibits the complement- and IgG-mediated neutrophil phagocytosis that may result from reduction of the expression of complement receptors, Fc receptors, and F-actin formation after ANE treatment. The findings suggest that areca nut chewing may jeopardize the defensive functions of neutrophils and affect periodontal health.

Endogenous anti-β-glucan antibodies as a potential predictive biomarker for clinical response to imprime PGG immunotherapy in non-small cell lung cancer (NSCLC) patients.

3045 Background: Imprime PGG (IPGG) is a yeast-derived β-1,3/1,6 glucan that primes innate immune cells to kill antibody-targeted cancer cells via a complement receptor 3 (CR3)-dependent mechanism. In humans, naturally occurring anti-β-glucan antibodies (ABA) are required for binding of IPGG to CR3 and subsequent changes in innate cell functions. Methods: In a 32-donor healthy volunteer study, using a qualified quantitative ELISA assay, ABA levels and the threshold for binding and modulation of innate immune functions were evaluated, including a) complement activation, b) complement receptor expression, c) activation marker modulation, and d) selective chemokine production. The potential of the ABA level as a clinical biomarker for clinical response to IPGG was evaluated in a Phase 2 clinical trial by retrospectively segregating subjects into populations at or above the ABA threshold (biomarker positive; BM+) or below the ABA threshold (biomarker negative; BM-). Advanced NSCLC patients received cetuximab,...

Endogenous anti-β-glucan antibodies, a potential predictive biomarker for the efficacy of soluble yeast β-1,3/1,6 glucan (Imprime PGG®) immunotherapy in cancer patients (VAC3P.947)

Abstract The innate immune response to Imprime PGG® (Imprime PGG) is being leveraged to develop a novel cancer immunotherapy in conjunction with anti-tumor monoclonal antibodies. Previous research has demonstrated the presence of endogenous anti-β-glucan antibodies (ABA) as a necessary prerequisite for the binding and functional activity of Imprime PGG in innate immune cells. In this study, healthy donors with varying levels of ABA were evaluated to determine the threshold of ABA above which binding and modulation of functions were observed. Donors who had ABA levels above the threshold showed Imprime PGG binding (> 5%) to their neutrophils and monocytes with significant modulation of functions, including, a) activation of complement (C5a), b) increased surface expression of complement receptor 3, c) modulation of activation markers (CD62L), and d) production of selective chemokines (IL-8). The potential of the ABA level being a clinical biomarker was then evaluated in a non-small cell lung cancer trial by segregating patients into biomarker (BM) positive or negative populations based on the established ABA threshold. The BM positive patients showed a significantly increased objective response rate and marked survival benefit not seen in the BM negative patients. These results demonstrate a successful translation of biomarker discovery in healthy donors to clinical utility in cancer patients. ABA is a potential predictive biomarker for efficacy of Imprime PGG immunotherapy.

Expression and regulation of complement receptors by human natural killer cells

Integration of cellular and humoral arms of the innate immune response is fundamental to the development of powerful effector functions in host defence as well as aberrant immune responses. Here, we provide evidence in support of the relationship between complement activation and NK cell functional modulation. We demonstrate that human NK cells and both CD56brightCD16− and CD56dimCD16+ populations express receptors known to detect the biologically active peptides C3a and C5a (i.e. C3aR, C5aR, C5L2) and the covalently-bound fragments C3b and metabolites iC3b and C3d which serve in immune adhesion (e.g. CR3, CR4). We also show that several pathogen- or tumour/inflammation-related stimuli differentially regulated those complement receptor expression. Furthermore, our results suggest that C3 fragments (C3a, iC3b) have a negative regulatory effect on IFN-γ production in NK cells. This work provides extensive information of human complement receptors relevant to the integrated actions of complement and NK cells which has been suggested by animal studies. The observations may act as a resource that allows further understanding and exploitation of role of complement in human health and immune mediated diseases.

In vitro activation of mouse neutrophils by recombinant human interferon-gamma: Increased phagocytosis and release of reactive oxygen species and pro-inflammatory cytokines

Here, we investigated the ability of IFN-γ to modulate the functions of mouse neutrophils in vitro. Neutrophils incubated in the presence of IFN-γ showed enhanced phagocytosis in response to zymosan, opsonized zymosan or precipitated immune complexes of IgG and ovalbumin. The effect of IFN-γ was dose-dependent with an initial response at 10 U/ml and a maximal response at 150 U/ml; 2 h of incubation were required to reach the optimal response level. These stimuli can also induce IFN-γ-pretreated neutrophils to release reactive oxygen species (ROS), such as superoxide anion, hydrogen peroxide and hypochlorous acid, as well as granule lysosomal enzymes and the pro-inflammatory cytokines TNF-α and IL-6. We found that increased expression of FcγR, dectin-1 and complement receptors (CRs) correlated with these effects in these cells. The enhancing effect of IFN-γ on the respiratory burst was found to be associated with up-regulation of the gp91(phox) and p47(phox) subunits of NADPH oxidase, as measured by their mRNA levels. The enhancing effect of IFN-γ on phagocytosis and ROS release may not only be relevant for the efficient killing of invading microorganisms, but may also produce oxidative stress on adjacent cells, resulting in a possible inflammatory role that could also be favored by the liberation of the pro-inflammatory cytokines TNF-α and IL-6.

Malaria Inhibits Surface Expression of Complement Receptor 1 in Monocytes/Macrophages, Causing Decreased Immune Complex Internalization

Complement receptor 1 (CR1) expressed on the surface of phagocytic cells binds complement-bound immune complexes (IC), playing an important role in the clearance of circulating IC. This receptor is critical to prevent accumulation of IC, which can contribute to inflammatory pathology. Accumulation of circulating IC is frequently observed during malaria, although the factors contributing to this accumulation are not clearly understood. We have observed that the surface expression of CR1 on monocytes/macrophages and B cells is strongly reduced in mice infected with Plasmodium yoelii, a rodent malaria model. Monocytes/macrophages from these infected mice present a specific inhibition of complement-mediated internalization of IC caused by the decreased CR1 expression. Accordingly, mice show accumulation of circulating IC and deposition of IC in the kidneys that inversely correlate with the decrease in CR1 surface expression. Our results indicate that malaria induces a significant decrease on surface CR1 expression in the monocyte/macrophage population that results in deficient internalization of IC by monocytes/macrophages. To determine whether this phenomenon is found in human malaria patients, we have analyzed 92 patients infected with either P. falciparum (22 patients) or P. vivax (70 patients) , the most prevalent human malaria parasites. The levels of surface CR1 on peripheral monocytes/macrophages and B cells of these patients show a significant decrease compared with uninfected control individuals in the same area. We propose that this decrease in CR1 plays an essential role in impaired IC clearance during malaria.

Beta-Thalassemia Minor Is Associated with IgA Nephropathy

Jung Hyun Kang, M.D., Bo Rha Park, M.D., Kyung Soo Kim, M.D., Do Yeun Kim, M.D., Hee Jin Huh, M.D., Seok Lae Chae, M.D., and Sung Joon Shin, M.D.. Ann Lab Med 2013;33:153-5. https://doi.org/10.3343/alm.2013.33.2.153

Modulations in the Expression of Leukocyte Complement Receptors (CR1 and CR2) in Rheumatoid Arthritis

Modulations in the Expression of Leukocyte Complement Receptors (CR1 and CR2) in Rheumatoid Arthritis

Expression of complement receptors 1 (CR1/CD35) and 2 (CR2/CD21), and co-signaling molecule CD19 in cattle

C3d is a sub-fragment of the C3 component of the complement system. Covalent binding of multiple C3ds to antigen reduces the activation threshold of cognate B lymphocytes by one thousand fold through co-ligation of the B cell antigen receptor (BCR) and complement receptor 2 (CR2/CD21). Reverse transcriptase polymerase chain reaction (RT-PCR) revealed that, in cattle, four distinct complement receptors are produced from the Cr2 gene by alternative splicing. Cattle express two major variants of the Cr2 gene representing homologues of murine CR1 and CR2, each of which is expressed in both a long and a short form. Expression of CR1 and CR2 was detected in IgM+ cells from both the spleen and peripheral blood. Additionally, the coding sequence of CD19, the CR2 co-signaling molecule, was determined. CD19 was confirmed to be expressed by IgM+ cells from the spleen and peripheral blood.

Complement receptor type 1 (CR1, CD35) is a potent inhibitor of B-cell functions in rheumatoid arthritis patients

The involvement of B cells, complement activation and subsequent immune complex deposition has all been implicated in the pathogenesis of rheumatoid arthritis (RA). Although the reduced expression of complement receptor 1 (CR1, CD35) and 2 (CR2, CD21) on the B cells of RA patients has been known for a long time, their exact role in B-cell tolerance and autoimmunity is not yet fully understood. To get a deeper insight into the possible mechanisms, we studied the expression and function of CR1 and CR2 on various subsets of B cells of healthy donors and RA patients at various stages of the disease by FACS analysis, (3)H-thymidine incorporation and ELISA. We found that CD19(+)CD27(-) naive B cells up-regulate the expression of the inhibitory CR1 during differentiation to CD19(+)CD27(+) memory B cells both in healthy donors and in RA patients, whereas the expression of the activatory CR2 is down-regulated. This clearly demonstrates that the expression of these two antagonistic complement receptors is regulated differentially during the development of human B cells, a phenomenon which may influence the maintenance of peripheral B-cell tolerance. Our functional studies show that after clustering CR1 both by its natural ligand and To5 mAb, the inhibitory function of CD35 is maintained in RA patients, despite its significantly reduced expression compared with healthy individuals. Besides blocking B-cell receptor-induced proliferation, CR1 inhibits the differentiation of B cells to plasmablasts and their immunoglobulin production. Since the reduced expression of CR1 in RA patients does not affect its inhibitory function, this receptor might serve as a new target for therapeutical interventions.

MicroRNA-155 enhances ocular inflammation after Pseudomonas aeruginosa infection (158.11)

Abstract Abstract: As a gene regulator, microRNA (miR)-155 plays an important role in both autoimmune inflammation as well as antiviral innate immunity. However, the role of miR-155 in Pseudomonas aeruginosa (PA) keratitis remains unknown. Our study demonstrated that miR-155 expression levels were significantly up-regulated in PA-infected vs normal human corneas as well as Macrophages derived from PBMC. Furthermore, in vivo studies showed that miR-155 expression was significantly increased in PA-infected corneas of C57BL/6 (B6) mice. Inhibition of miR-155 led to reduced ocular disease after PA infection, by down-regulating pro-inflammatory cytokine (e.g., IL-1β, IFN-γ, IL-6, IL-12) production. In vitro studies also demonstrated that PA challenge induced miR-155 expression in a time- and dose-dependent manner in peritoneal Macrophages and RAW264.7 cells. The induction of miR-155 was dependent on TLR2, TLR4, TLR9, through NF-κB, IKK, JNK and PI3K, but not P38 or ERK pathways. Moreover, overexpression of miR-155 significantly decreased Macrophage-mediated phagocytosis and intracellular bacterial killing of PA, by down-regulating expression of mannose receptor (MR) and complement receptor 3 (CR3). miR-155 overexpression also enhanced the production of pro-inflammatory cytokines including IFN-γ, IL-1β, IL-6, IL-12, IL-17A, but reduced anti-inflammatory cytokine IL-10 expression. Collectively, these data indicated that miR-155 functions as an inflammatory amplifier in PA keratitis.

Expression of complement components, receptors and regulators by human dendritic cells

Integration of innate and adaptive arms of the immune response at a cellular and molecular level appears to be fundamental to the development of powerful effector functions in host defence and aberrant immune responses. Here we provide evidence that the functions of human complement activation and antigen presentation converge on dendritic cells (DCs). We show that several subsets of human DCs [i.e., monocyte derived (CD1a+CD14−), dermal (CD1a+DC-SIGN+), Langerhans (CD1a+Langerin+), myeloid (CD1c+CD19−), plamacytoid (CD45RA+CD123+)] express many of the components of the classical and alternative and terminal pathways of complement. Moreover human DCs have receptors known to detect the biologically active peptides C3a and C5a (C3aR, C5aR) and the covalently bound fragments C3b and metabolites iC3b and C3d which serve in immune adhesion (i.e., CR3, CR4, CRIg). We also show that the human DC surface is characterised by membrane bound regulators of complement activation, which are also known to participate in intracellular signalling (i.e., CD46, CD55, CD59). This work provides an extensive description of complement components relevant to the integrated actions of complement and DC, illuminated by animal studies. It acts as a resource that allows further understanding and exploitation of role of complement in human health and immune mediated diseases.

Minimal Association of Common Red Blood Cell Polymorphisms with Plasmodium falciparum Infection and Uncomplicated Malaria in Papua New Guinean School Children

Southeast Asian ovalocytosis (SAO), α(+)-thalassemia, and low expression of complement receptor 1 (CR1) have been associated with protection against severe Plasmodium falciparum malaria. In a cohort of children 5-14 years of age the effect of α(+)-thalassemia, SAO (SLC4A1Δ27), CR1 polymorphisms, and Gerbich negativity (GYPCΔex3) on risk of P. falciparum infections and uncomplicated illness were evaluated. The risk of acquiring polymerase chain reaction (PCR)-diagnosed P. falciparum infections was significantly lower for α(+)-thalassemia heterozygotes (hazard ratio [HR]: 0.56) and homozygotes (HR: 0.51) than wild-type children. No such differences were seen in light of microscopy diagnosed infections (P = 0.71) or were α(+)-thalassemia genotypes associated with a reduced risk of uncomplicated P. falciparum malaria. No significant associations between the risk of P. falciparum infection or illness were observed for any of the other red blood cell polymorphisms (P > 0.2). This suggests that these polymorphisms are not associated with significant protection against P. falciparum blood-stage infection or uncomplicated malaria in school-aged children.

Measurement of complement receptor 1 on neutrophils in bacterial and viral pneumonia

Objective To study the different expression of complement receptors on neutrophils between bacterial and viral pneumonia. Methods Fifty-nine patients with CAP were studied prospectively. CR1 ,CR3 were measured by,using flow cytometer. ESR,CRP and WBC were also measured. Results Thirteen patients had pneumococcal pneumonia; 13 patients, A type of infuenza virus pneumonia ;5 patients, atypical pneumonia, and 28 patients, aetiologically undefined pneumonia. The mean expression of complement receptor 1 ( CR1 ) on neutrophils and aetiologically undefined pneumonia was( 19.4 ± 9.8 ) and ( 19.3 ± 8.8), which were significantly higher than those with A type of infuenza virus( t = 6.13,5.09 ,P < 0.01 ). Conclusion The expression of CR1 may be of value as an additional rapid tool in the aetiological diagnosis, bacterial or viral infection of CAP. Key words: Community-acquired pneumonia; Complement receptor

Expression of complement components, receptors and regulators by human dendritic cells and the role of C3a and C5a in modulation of dendritic cell function

Expression of complement components, receptors and regulators by human dendritic cells and the role of C3a and C5a in modulation of dendritic cell function

Expression of complement receptor 2 (CD21), membrane IgM and the inhibitory receptor CD32 (FcγRIIb) in the lymphoid tissues of neonatal calves

Limited active antibody responses in neonates following vaccination have been attributed to immaturity of the immune system and to the suppressive effects of maternal antibodies. The activating receptor CD21 (CR2), when co-ligated with membrane IgM (mIgM) by complement-bound antigen lowers the threshold for activation of B lymphocytes. The inhibitory receptor CD32 (FcγRII) when co-ligated with mIgM by antigen–antibody complexes raises the threshold for activation. Expression of these receptors, which potentially play roles in regulation of B cell responses in the presence of maternal antibodies in neonates, has been recently characterized in blood lymphocytes in neonatal calves. Little is known however about expression of these receptors in the lymphoid tissues, where immune responses are initiated. In this study, expression of CD21, mIgM and CD32 receptors by B lymphocytes was studied in a range of lymphoid tissues including spleen, lymph nodes and bone marrow from newborn and 7-week-old calves using flow cytometry. The proportion of naïve B lymphocytes in the lymphocyte gate was significantly lower in blood and spleen of newborn calves compared to 7-week-old calves. Over 90% of B lymphocytes expressed CD21 in the lymphoid tissues. In the lymph nodes and spleen, a lower proportion of mIgM + B lymphocytes expressed CD32 compared to blood. In addition, intensity of expression of CD32 on B cells in lymph nodes was significantly lower compared to that in blood, suggesting a lower potential for inhibitory signalling in B cells in the lymphoid microenvironment. Investigation of the CD5 + B cell population (as an indicator of B1 B cells) suggested an increase in the proportion of IgM +CD5 + cells with age in calves, in both blood and lymphoid tissue, in contrast to the situation in humans and mice. Overall, the majority of naïve B lymphocytes in lymphoid tissues in neonatal calves expressed both activating (CD21, mIgM) and inhibitory (CD32) receptors. These receptors may provide targets for novel adjuvants, to lower the threshold for activation of B cells in neonates, and enhance antibody responses.