Consistency of effects of tropical-forest disturbance on species composition and richness relative to use of indicator taxa.

Lawton et al. (1998) found, in a highly cited study, that the species richness of 8 taxa each responds differently to anthropogenic disturbance in Cameroon forests. Recent developments in conservation science suggest that net number of species is an insensitive measure of change and that understanding which species are affected by disturbance is more important. It is also recognized that all disturbance types are not equal in their effect on species and that grouping species according to function rather than taxonomy is more informative of responses of biodiversity to change. In a reanalysis of most of the original Cameroon data set (canopy and ground ants, termites, canopy beetles, nematodes, and butterflies), we focused on changes in species and functional composition rather than richness and used a more inclusive measure of forest disturbance based on 4 component drivers of change: years since disturbance, tree cover, soil compaction, and degree of tree removal. Effects of disturbance on compositional change were largely concordant between taxa. Contrary to Lawton et al.'s findings, species richness for most groups did not decline with disturbance level, providing support for the view that trends in species richness at local scales do not reflect the resilience of ecosystems to disturbance. Disturbance affected species composition more strongly than species richness for butterflies, canopy beetles, and litter ants. For these groups, disturbance caused species replacements rather than just species loss. Only termites showed effects of disturbance on species richness but not composition, indicating species loss without replacement. Although disturbance generally caused changes in composition, the strength of this relationship depended on the disturbance driver. Butterflies, litter ants, and nematodes were correlated with amount of tree cover, canopy beetles were most strongly correlated with time since disturbance, and termites were most strongly correlated with degree of soil disturbance. There were moderately divergent responses to disturbance between functional feeding groups. Disturbance was most strongly correlated with compositional differences of herbivores within beetles and nematodes and humus feeders within termites. Our results suggest that consideration of the impact of different forms of disturbance on species and functional composition, rather than on net numbers of species, is important when assessing the impacts of disturbance on biodiversity.

Suppression of savanna ants alters invertebrate composition and influences key ecosystem processes.

In almost every ecosystem, ants (Hymenoptera: Formicidae) are the dominant terrestrial invertebrate group. Their functional value was highlighted by Wilson (1987) who famously declared that invertebrates are the "little things that run the world." However, while it is generally accepted that ants fulfil important functions, few studies have tested these assumptions and demonstrated what happens in their absence. We report on a novel large-scale field experiment in undisturbed savanna habitat where we examined how ants influence the abundance of other invertebrate taxa in the system, and affect the key processes of decomposition and herbivory. Our experiment demonstrated that ants suppressed the abundance and activity of beetles, millipedes, and termites, and also influenced decomposition rates and levels of herbivory. Our study is the first to show that top-down control of termites by ants can have important ecosystem consequences. Further studies are needed to elucidate the effects ant communities have on other aspects of the ecosystem (e.g., soils, nutrient cycling, the microbial community) and how their relative importance for ecosystem function varies among ecosystem types (e.g., savanna vs. forest).

Vertical transmission as the key to the colonization of Madagascar by fungus-growing termites?

The mutualism between fungus-growing termites (Macrotermitinae) and their mutualistic fungi (Termitomyces) began in Africa. The fungus-growing termites have secondarily colonized Madagascar and only a subset of the genera found in Africa is found on this isolated island. Successful long-distance colonization may have been severely constrained by the obligate interaction of the termites with fungal symbionts and the need to acquire these symbionts secondarily from the environment for most species (horizontal symbiont transmission). Consistent with this hypothesis, we show that all extant species of fungus-growing termites of Madagascar are the result of a single colonization event of termites belonging to one of the only two groups with vertical symbiont transmission, and we date this event at approximately 13 Mya (Middle/Upper Miocene). Vertical symbiont transmission may therefore have facilitated long-distance dispersal since both partners disperse together. In contrast to their termite hosts, the fungal symbionts have colonized Madagascar multiple times, suggesting that the presence of fungus-growing termites may have facilitated secondary colonizations of the symbiont. Our findings indicate that the absence of the right symbionts in a new environment can prevent long-distance dispersal of symbioses relying on horizontal symbiont acquisition.

Assessing association of common variation in the C1Q gene cluster with systemic lupus erythematosus.

Recent studies have tested genetic variation at the C1QA, C1QB and C1QC (complement component 1, q subcomponent, A chain, complement component 1, q subcomponent, B chain and complement component 1, q subcomponent, c chain) loci in relation to systemic lupus erythematosus (SLE) risk. Evidence for a significant effect of C1Q locus gene polymorphisms on SLE predisposition remains unclear. We aimed to identify associations between common C1Q polymorphisms and SLE risk and serum C1q, C3 and C4 levels. We performed family-based association tests in 295 nuclear families with one affected proband. Tag-single nucleotide polymorphisms (SNPs) ranging from 35.4 kb upstream of the C1QA gene to 28 kb downstream of the C1QB gene were selected to represent the entire C1Q gene locus. We performed transmission disequilibrium tests for affectation status and continuous traits, including C1q, C3 and C4 levels using family-based association tests (FBAT). There was no evidence for a significant role of C1Q locus gene polymorphisms in SLE risk predisposition. The strongest association was observed with a variant in the 3'UTR region of the C1QB gene (rs294223, P = 0.06). We found nominally significant associations with a second variant (rs7549888) in the 3'UTR region of the C1QB gene and C1q (P = 0.01), C3 (P = 0.004) and C4 levels (P = 0.01). In a large family-based association study of C1Q gene cluster polymorphisms no evidence for a genetic role of C1Q locus SNP in SLE risk predisposition was obtained in patients of European ancestry. This is in contrast to other cohorts, in which single variants associated with C1Q, C3 and C4 levels and nephritis have been studied and shown associations.

C1q--how many functions? How many receptors?

C1, the first component of the classical pathway of complement activation is a complex of three proteins called C1q, C1r and C1s. Normally, C1q binding to aggregated IgG molecules results in activation of the classical pathway of complement. However, C1q has a number of other observed functions, not directly related to complement, that could be mediated by recently identified binding proteins acting as cell-surface receptors or soluble modulators of C1q-mediated functions. This article discusses the various activities of C1q and the evidence that these functions might be influenced by both membrane-bound and soluble C1q-binding proteins.

The ins and outs of calreticulin: from the ER lumen to the extracellular space.

Calreticulin was first isolated 26 years ago. Since its discovery as a minor Ca(2+)-binding protein of the sarcoplasmic reticulum, the appreciation of its importance has grown, and it is now recognized to be a multifunctional protein, most abundant in the endoplasmic reticulum (ER). The protein has well-recognized physiological roles in the ER as a molecular chaperone and Ca(2+)-signalling molecule. However, it has also been found in other membrane-bound organelles, at the cell surface and in the extracellular environment, where it has recently been shown to exert a number of physiological and pathological effects. Here, we will focus on these less-well-characterized functions of calreticulin.

Termites mitigate the effects of drought in tropical rainforest.

Termites perform key ecological functions in tropical ecosystems, are strongly affected by variation in rainfall, and respond negatively to habitat disturbance. However, it is not known how the projected increase in frequency and severity of droughts in tropical rainforests will alter termite communities and the maintenance of ecosystem processes. Using a large-scale termite suppression experiment, we found that termite activity and abundance increased during drought in a Bornean forest. This increase resulted in accelerated litter decomposition, elevated soil moisture, greater soil nutrient heterogeneity, and higher seedling survival rates during the extreme El Niño drought of 2015-2016. Our work shows how an invertebrate group enhances ecosystem resistance to drought, providing evidence that the dual stressors of climate change and anthropogenic shifts in biotic communities will have various negative consequences for the maintenance of rainforest ecosystems.

Consequence of neo-antigenicity of the 'altered self'.

Post-translational modifications play a central role in determining the function of proteins. Such protein modifications come in a great variety of guises, and include phosphorylation, proteolysis, glycosylation, citrullination and oxidative modifications. In relation to inflammatory autoimmune diseases, some post-translational modifications appear to result in the generation of new antigens, and hence autoantibodies. Examples include: the induction of peptide immunogenicity by the spontaneous conversion of aspartic acid residues to isoaspartic acid; granzyme B-mediated cleavage of SLE autoantigens; the oxidative modification--on the surface of apoptotic cells--of lipids and proteins, rendering them immunogenic; and the presence of antibodies to oxidatively modified type II collagen and C1q in RA and SLE patients, respectively. The measurement of autoantibodies to citrullinated proteins has been verified as a very useful diagnostic tool in RA. Proteomics techniques, in principle, allow the detection of all types of in vivo protein modifications, and the increasing application of such technologies to the study of rheumatological diseases will further our understanding of autoantigenicity.

Identification of a gC1q-binding protein (gC1q-R) on the surface of human neutrophils. Subcellular localization and binding properties in comparison with the cC1q-R.

Human neutrophils have multiple C1q-binding proteins. Direct ligand-binding studies with the globular domain of C1q and two-dimensional Western blot analysis revealed two gC1q-binding proteins (gC1q-R): a 33,000 M(r) protein (pI 4.5) mainly in the neutrophil plasma membrane and an 80,000-90,000 M(r) protein (pI 4.1-4.2) located mainly in the granules. Direct binding studies showed that C1q bound to this higher molecular weight protein under physiological conditions. In contrast, anti-cC1q-R antibody, which recognizes a protein binding to collagenous tails of C1q, detected only a 68,000 M(r) protein in the plasma membrane. Both the 33,000 and 68,000 M(r) receptors appear early on the surface of differentiating HL-60 cells. On mature neutrophils, surface expression of both C1q receptors was evident, but no upregulation was observed upon stimulation. Phorbol myristate acetate treatment of neutrophils downregulated both the receptors from cell surface, and significant amounts of soluble gC1q-R were in cell media supernatants, suggesting receptor shedding or secretion. gC1q-R, unlike cC1q-R, did not bind to other C1q-like ligands, namely mannose binding protein, surfactant protein-A, surfactant protein-D, or conglutinin under normal ionic conditions, suggesting a greater specificity for C1q than the "collectin" type receptor (cC1q-R). Rather, gC1q-R only bound purified C1q, and the binding was enhanced under low ionic conditions and in the absence of calcium. The role of C1q receptor shedding and its biologic consequence remain to be defined, but may contribute to the diversity of C1q-mediated responses observed in many cell types.

Evidence for a protective role of pulmonary surfactant protein D (SP-D) against influenza A viruses.

We tested the hypothesis that pulmonary surfactant-associated lectins--surfactant proteins A and D (SP-A, and -D)--contribute to initial protective mechanisms against influenza A viruses (IAVs). SP-D potently inhibited hemagglutination activity of several strains of IAV as well as causing viral aggregation. SP-D enhanced neutrophil binding of IAV and neutrophil respiratory burst responses to the virus. Neutrophil dysfunction resulting from IAV exposure was diminished when the virus was pre-incubated with SP-D. Each of these effects was mediated by the calcium-dependent carbohydrate-binding property of SP-D. Native SP-D preparations of both human and rat origin, as well as recombinant rat SP-D, had similar activity. SP-A also inhibited IAV hemagglutination activity. We have previously reported that related mammalian serum lectins (mannose-binding lectin [MBL] and conglutinin) have similar effects. SP-D was at least 10-fold more potent at causing hemagglutination inhibition than were SP-A or MBL. SP-D was shown to contribute to potent anti-IAV activity of human bronchoalveolar lavage fluid. These results suggest that SP-D--alone, and in conjunction with SP-A and phagocytic cells--constitutes an important component of the natural immune response to IAV infection within the respiratory tract.

Lung surfactant proteins involved in innate immunity.

The two lung surfactant collectins, surfactant protein (SP)-A and SP-D, are involved in host defence against infectious and allergenic agents via enhancement of killing and clearance by macrophages and neutrophils. Recent gene-knockout, protein engineering and physiological studies have emphasised the roles that SP-A and SP-D play in acute inflammatory responses.

Heightened autoantibody immune response to citrullinated calreticulin in bronchiectasis: Implications for rheumatoid arthritis.

Calreticulin (CRT) and citrullinated (citCRT) are implicated in rheumatoid arthritis (RA) pathology. citCRT binds to RA shared epitopes (SE) on HLA-DR molecules with high affinity and triggers pro-inflammatory events in adjacent cells. The aim of the study was to detect the presence of citCRT prior to developing RA and evaluate if citCT is a target for autoantibodies in RA cohorts with and without lung disease. Antibodies were assessed by ELISA against native CRT, citCRT and general protein citrullination, in sera from 50 RA patients without lung disease, 122 bronchiectasis (BR) patients, 52 bronchiectasis patients with RA (BRRA), 87 asthma patients and 77 healthy controls (HC). Serum citCRT was detected by immunoblotting and mass spectrometry. Genomic DNA was genotyped for HLA-DRB1 alleles. Patients were assessed for DAS28, rheumatoid factor, and anti-cyclic citrullinated peptide antibodies. Extracellular citCRT was detected in BR patients sera prior to them developing RA. A citCRT SE binding peptide GEWKPR261citQIDNPDYK was identified. Anti-CRT antibodies were observed in 18% of BR patients with or without RA. Anti-citCRT antibodies were observed in ∼35% of BR or RA patients, increasing to 58% in BRRA patients. In the RA alone patients 7/20 (35%) who were negative for RF and anti-CCP were anti-CRT antibody positive and had higher DAS28 scores than triple negative RA alone patients. Three of the four BR patients who developed RA over 18 months were anti-citCRT+ve SE+ve. The detection of citCRT in BR and development of anti-citCRT in BR patients suggests citCRT antigens are early targets of antigenicity in these patients, especially in SE+ve patients prior to the onset of RA.

Priming action of inositol hexakisphosphate (InsP6) on the stimulated respiratory burst in human neutrophils.

After priming by a number of different host, bacterial and chemical agents, human neutrophils may be stimulated to produce a greater respiratory burst than would be elicited by the stimulus alone. Other neutrophil functions may be similarly enhanced by pre-exposure to a priming agent. We describe here a new extracellular role for inositol hexakisphosphate (InsP6) as a priming agent for a variety of human neutrophil functional responses. Preincubation of the cells with InsP6 alone (up to 250 microM) has no stimulatory effect upon the basal production of reactive oxygen intermediates but the response to a subsequent stimulus (FMLP, PMA or phagocytic particles) is substantially enhanced. Levels 100-200% higher than 'stimulus only' controls have been recorded. Peak enhancement of the FMLP-induced oxidative response occurs after 1-2 min preincubation with InsP6 and the effect is dose-dependent (maximum at approx. 100 microM InsP6). As others have shown FMLP stimulation of superoxide anion production has no external Ca2+ dependence but the presence of low levels of Ca2+ and Mg2+ (0.1 mM) during priming appears to be an essential requirement for full expression. Reports of intracellular concentrations of InsP6 in mammalian cells in the 30-100 microM range suggest that the local release of this inositol polyphosphate from damaged or effect cells could have a physiologically important modulatory role on neutrophil functions.

The role of surfactant protein D in the colonisation of the respiratory tract and onset of bacteraemia during pneumococcal pneumonia.

We have shown previously that surfactant protein D (SP-D) binds and agglutinates Streptococcus pneumoniae in vitro. In this study, the role of SP-D in innate immunity against S. pneumoniae was investigated in vivo, by comparing the outcome of intranasal infection in surfactant protein D deficient (SP-D-/-) to wildtype mice (SP-D+/+). Deficiency of SP-D was associated with enhanced colonisation and infection of the upper and lower respiratory tract and earlier onset and longer persistence of bacteraemia. Recruitment of neutrophils to inflammatory sites in the lung was similar in both strains mice in the first 24 hrs post-infection, but different by 48 hrs. T cell influx was greatly enhanced in SP-D-/- mice as compared to SP-D+/+ mice. Our data provides evidence that SP-D has a significant role to play in the clearance of pneumococci during the early stages of infection in both pulmonary sites and blood.

Heterogeneity in the circulating neutrophil pool: studies on subpopulations separated by continuous flow electrophoresis.

Isolated blood neutrophils from healthy individuals have been separated by continuous flow electrophoresis (CFE) as a Gaussian-shaped profile extending over 12-15 fractions, on the basis of differences in cell surface electrical charge. The fractions were pooled into three or four subpopulations; the mean electrophoretic mobilities of the least and most electronegative cells were 0.96 and 1.22 microns/sec/V/cm, respectively. Each pool of neutrophils was analyzed for functional and biochemical differences. Expression of respiratory burst in terms of the rate of superoxide production by the least and most electronegative cells to fixed concentrations of N-formyl-methionyl-leucyl-phenylalanine (fMLP, 10(-7) M) or phorbol myristate acetate (PMA, 1 microgram/ml) revealed that the least electronegative cells generated superoxide anion (O2-) at approximately twice the rate of the most electronegative cells. However, when lower concentrations of fMLP were used (1-5 x 10(-9) M), the most electronegative cells were most active. The least electronegative cells were also the most active in terms of phagocytosis and chemotaxis. In accordance with these differences in motile function, the basal F-actin content of the least electronegative cell pool was greater than the F-actin levels found in the most electronegative cells and remained so upon stimulation with fMLP. Such neutrophil heterogeneity as detected by CFE may be important in selective margination and recruitment of cells to inflammatory foci and sites of infection and may in part represent subsets of cells within the circulation that are primed in vivo to respond to inflammatory stimuli.

Fractionation of human neutrophils into subpopulations by countercurrent distribution: surface charge and functional heterogeneity.

Isolated blood neutrophils from normal healthy subjects were separated into fractions by sequential countercurrent distribution (CCD) in a charge-sensitive dextran/polyethylene glycol aqueous phase system. The neutrophils separated as a broad profile, and in a charged phase procedure the separation was based upon differences in cell surface electrokinetic properties, as confirmed by electrophoretic mobility measurements of fractions across the profile using analytical cytopherometry. The CCD cell fractions were generally pooled as three or four major subfractions for analysis of functional and metabolic differences. These included measurements of chemotaxis, phagocytosis, and respiratory burst. An inverse relationship was found between the electrophoretic mobility (EPM) of the subfraction pools and their functional competence, with the less electronegative cell fraction pools often as much as 2 to 3-fold more active than the more electronegative pools. This demonstration of electrokinetic and functional heterogeneity in 'resting' neutrophil subpopulations separated by CCD may reflect changes during their sojourn in the circulation that determine selective margination and recruitment of cells to inflammatory foci and sites of infection.

Modular organization of carbohydrate recognition domains in animal lectins.

In spite of the great diversity of animal lectins, a common characteristic is their ability to bind sugars by means of discrete, modular carbohydrate recognition domains, CRDs. Three different groups of animal lectins-galectins, P-type and C-type lectins- have different types of CRDs which they arrange in a number of combinations, in three dimensions, in order to increase the affinity for oligosaccharides associated with glycoconjugates. The necessity of combining multiple CRDs in a native lectin molecule in order to increase the affinity for multiple ligands is of great importance physiologically, since many of the carbohydrate structures associated with proteins exist in a variety of different conformations. Recent work has clarified the structural basis for carbohydrate recognition by some of these lectins.

Rapid method for the isolation of neutrophils in high yield without the use of dextran or density gradient polymers.

A simple, rapid and economical method for the isolation of polymorphonuclear leucocytes (PMNs) from whole blood is compared with dextran and dextran/Lymphoprep gradient techniques. The method eliminates the use of dextran and density gradient polymers such as Ficoll which have been shown to affect PMNs adversely. The technique is based on the lysis of red cells with isotonic ammonium chloride solution followed by differential centrifugation to separate the PMNs. This method gave a PMN yield of 73% (SD +/- 3.5) and a purity of 78% (SD +/- 2.5). Both morphology and functional activity were preserved, as assessed by bacterial phagocytosis and killing, chemotaxis, polarising response, superoxide production and adherence. In contrast, the dextran and dextran/Lymphoprep techniques gave yields of 50% and 15% with purities of 78% and 91% respectively. In a series of 14 PMN isolations, the differential centrifugation method gave an average yield of 63% with an average purity of 83%.

Effect of IP6 on human neutrophil cytokine production and cell morphology.

Inositol hexaphosphate (IP6) has anti-cancer properties, but recently other extracellular functions have been observed for IP6, including enhancing superoxide production and phagocytosis by neutrophils in the presence of microbial stimuli. This study investigated other inflammatory functions of IP6 on adherent neutrophils. The effect of IP6 on the release of IL-8, tumour necrosis factor (TNF-alpha) and IL-6 by neutrophils attached to either plastic or laminin for up to 6 hours in response to stimulation with lipopolysaccharide or N-formyl-Met-Leu-Phe (fMLP) was investigated. An increase in IL-8 secretion by stimulated cells occurred in the presence of IP6. The incubation of cells attached to laminin with IP6 alone (100-250 BM) did not effect cell morphology, but in the presence of 10(-7) M fMLP altered cell shape. A direct effect of IP6 on cell function was to trigger a sustained assembly of F-actin. Thus, exposure of neutrophils to low levels of IP6 appears to modulate selective neutrophil functions.