Independent and Cooperative Roles of Adaptor Molecules in Proximal Signaling during Fc?RI-Mediated Mast Cell Activation

Activation through FcɛRI, a high-affinity IgE-binding receptor, is critical for mast cell function during allergy. The formation of a multimolecular proximal signaling complex nucleated by the adaptor molecules SLP-76 and LAT1 is required for activation through this receptor. Based on previous T-cell studies, current dogma dictates that LAT1 is required for plasma membrane recruitment and function of SLP-76. Unexpectedly, we found that the recruitment and phosphorylation of SLP-76 were preserved in LAT1^−/− mast cells and that SLP-76^−/− and LAT1^−/− mast cells harbored distinct functional and biochemical defects. The LAT1-like molecule LAT2 was responsible for the preserved membrane localization and phosphorylation of SLP-76 in LAT1^−/− mast cells. Although LAT2 supported SLP-76 phosphorylation and recruitment to the plasma membrane, LAT2 only partially compensated for LAT1-mediated cell signaling due to its decreased ability to stabilize interactions with phospholipase Cγ (PLCγ). Comparison of SLP-76^−/− LAT1^−/− and SLP-76^−/− mast cells revealed that some functions of LAT1 could occur independently of SLP-76. We propose that while SLP-76 and LAT1 depend on each other for many of their functions, LAT2/SLP-76 interactions and SLP-76-independent LAT1 functions also mediate a positive signaling pathway downstream of FcɛRI in mast cells.Mast cell activation during allergic inflammation is mediated by the high-affinity immunoglobulin E (IgE)-binding receptor FcɛRI. Cross-linking of FcɛRI on mast cells by IgE/cognate antigen complexes results in the rapid release of a wide array of inflammatory mediators, including vasoactive amines and cytokines/chemokines that give rise to allergic symptoms, ranging in severity from simple urticaria to anaphylactic shock and death (14). As allergy affects ∼30% of the population in developed countries (13), much attention has been placed on studying the signal transduction mechanisms involved in mast cell activation downstream of FcɛRI in hopes of finding novel targets for therapeutic intervention.Signal transduction downstream of FcɛRI is initiated by the phosphorylation of the immunoreceptor tyrosine-based activation motifs (ITAMs) contained in the signaling components (β and γ chains) of the FcɛRI complex (30, 37). Once phosphorylated, these chains serve as docking sites for several protein tyrosine kinases (PTKs), including Lyn and spleen tyrosine kinase (Syk) (9, 19, 34). Recruitment of Syk to the membrane by FcɛRI results in the phosphorylation of scaffold proteins known as adaptor molecules. Adaptor proteins lack enzymatic activity but instead contain protein-binding domains that are critical for the formation of a multimolecular complex, which orchestrates downstream signaling in a temporal and spatial manner. The adaptor molecules Src homology 2 (SH2) domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76) and linker of activated T cells 1 (LAT1) organize the assembly of a proximal signaling complex downstream of FcɛRI. Failure to form this complex is detrimental to FcɛRI-mediated mast cell function, as demonstrated by the finding that both SLP-76-deficient (22, 29, 41) and LAT1-deficient (25, 31, 32) mast cells display severely diminished degranulation and cytokine/chemokine production following FcɛRI ligation.Similar proximal signaling complexes are formed downstream of several different ITAM-containing receptors. Much of our understanding of the role of adaptor molecules in signal transduction has come from identification of phosphoproteins during T-cell receptor (TCR)-mediated activation of the human Jurkat T-cell line (1, 33). These studies eventually led to a paradigm describing the sequence of events in the formation of the SLP-76/LAT1 signaling complex. According to this model, SLP-76 is found constitutively bound to Grb2-related adaptor downstream of Shc (GADS) (24) and resides in the cytosol. Upon TCR activation, the tyrosines of membrane-resident LAT1 are phosphorylated and become attachment sites for proteins such as phospholipase Cγ (PLCγ) and GADS (43, 45). SLP-76 is drawn to the membrane through a GADS/LAT1 interaction, which then permits Syk family PTKs to maximally phosphorylate the N-terminal tyrosines of SLP-76 (5, 10). Several lines of evidence support this model whereby a LAT1/SLP-76 module organizes TCR signaling. First, both SLP-76- and LAT1-deficient Jurkat T cells display similar biochemical defects, such as diminished PLCγ and extracellular signal-regulated kinase (ERK) activation (10, 42). Second, T cells in SLP-76^−/− and LAT1^−/− mice are blocked at the same stage of development (7, 44). Third, SLP-76 can be coimmunoprecipitated with LAT1 but not with LAT1 harboring tyrosine-to-phenylalanine mutations (45). Finally, expression of a fusion protein comprised of the membrane-localizing domain of LAT1 and SLP-76 that forces localization of SLP-76 to the plasma membrane rescues the TCR-induced functional defects of both SLP-76- and LAT1-deficient Jurkat T cells (3). This model implies a mutually dependent relationship between SLP-76 and LAT1, where SLP-76 and LAT1 rely on each other to carry out their roles.One might suspect that this model for LAT1/SLP-76 function would operate in all other cells that utilize these adaptor molecules for ITAM-containing receptor-mediated signaling. However, the published defects of LAT1-deficient mast cells in FcɛRI-mediated signaling appeared milder than those of SLP-76-deficient mast cells, although a direct comparison has never been reported. In the present study, we show that LAT1-deficient mast cells display distinct functional and biochemical defects compared to SLP-76-deficient mast cells, implying that unlike in T cells, SLP-76 may not depend entirely on LAT1 for its function in mast cells. Surprisingly, the membrane recruitment and phosphorylation of SLP-76 were also preserved in LAT1^−/− mast cells. We show that LAT2 (also known as non-T-cell activation linker [NTAL] or linker for activation of B cells [LAB]), which is not expressed in naïve T cells but is expressed in mast cells (15), is responsible for phosphorylation and plasma membrane recruitment of SLP-76 in the absence of LAT1. However, LAT2 cannot support all LAT1/SLP-76-associated functions, such as sustained Ca²⁺ flux, likely due to decreased stability of the LAT2/SLP-76/PLCγ complex. Comparison of SLP-76^−/− LAT1^−/− and SLP-76^−/− mast cells also revealed that some functions of LAT1 could occur independently of SLP-76. We propose that although SLP-76 and LAT1 are interdependent for many of their functions, LAT2/SLP-76 interactions and SLP-76-independent LAT1 functions mediate positive signaling downstream of FcɛRI in mast cells.     

Cooperative breeding: a question of climate?

In some species, including humans, parents receive help with offspring care. A new comparative study suggests that birds breed cooperatively when environmental conditions vary. Further empirical and theoretical work will be required to understand the evolutionary significance of this insight.     

Does Campylobacter jejuni Form Biofilms in Food-Related Environments?

Campylobacter jejuni is one of the most frequent causes of bacterial gastrointestinal food-borne infection worldwide. This species is part of the normal flora of the gastrointestinal tracts of animals used for food production, including poultry, which is regarded as the primary source of human Campylobacter infections. The survival and persistence of C. jejuni in food processing environments, especially in poultry processing plants, represent significant risk factors that contribute to the spread of this pathogen through the food chain. Compared to other food-borne pathogens, C. jejuni is more fastidious in its growth requirements and is very susceptible to various environmental stressors. Biofilm formation is suggested to play a significant role in the survival of C. jejuni in the food production and processing environment. The aims of this minireview were (i) to examine the evidence that C. jejuni forms biofilms and (ii) to establish the extent to which reported and largely laboratory-based studies of C. jejuni biofilms provide evidence for biofilm formation by this pathogen in food processing environments. Overall existing studies do not provide strong evidence for biofilm formation (as usually defined) by most C. jejuni strains in food-related environments under the combined conditions of atmosphere, temperature, and shear that they are likely to encounter. Simple attachment to and survival on surfaces and in existing biofilms of other species are far more likely to contribute to C. jejuni survival in food-related environments based on our current understanding of this species.     

Activation of development in mammals: is there a role for a sperm cytosolic factor?

In mammalian oocytes, fertilization-associated calcium [Ca2+]i oscillations are responsible for the activation of development. The mechanism(s) by which the sperm triggers the initial [Ca2+]i rise and supports long-lasting oscillations is not resolved. It has been proposed that the sperm may interact with receptors in the oocyte's plasma membrane and engage intracellular signaling pathways that result in Ca2+ release. A different line of investigation suggests that upon sperm-oocyte fusion, a sperm cytosolic factor is released into the oocyte which interacts with unknown cytosolic targets, and generates [Ca2+]i oscillations. We will discuss the most recent evidence for both lines of thought and demonstrate that injections of sperm crude extracts (SF) into mammalian oocytes trigger [Ca2+]i oscillations that support in vitro parthenogenetic development to the blastocyst stage.     

Cooperative hunting in a discrete predator–prey system II

ABSTRACT

We investigate a discrete-time predator–prey system with cooperative hunting in the predators proposed by Chow et al. by determining local stability of the interior steady states analytically in certain parameter regimes. The system can have either zero, one or two interior steady states. We provide criteria for the stability of interior steady states when the system has either one or two interior steady states. Numerical examples are presented to confirm our analytical findings. It is concluded that cooperative hunting of the predators can promote predator persistence but may also drive the predator to a sudden extinction.     

Variation in Trill Characteristics in Tree Pipit Songs: Different Trills for Different Use?

Transmitting information about singer's quality is an important function of song in many bird species, and this information should be useful in territorial interactions. Fast trills, being physically demanding song structures, are particularly suitable candidates for signalling of quality or aggressive motivation. We have evaluated trill characteristics in songs within a population of the Tree Pipit, a common European songbird with no sexual dimorphism, in which song apparently plays a key role in territory defence as well as mate choice. Two types of relatively fast trills (each of them in multiple variants differing in complexity) were commonly observed in repertoires of Tree Pipit males. Trill rates significantly differed among individuals, suggesting that these song structures may carry information about male quality in this species. We tested by playback experiments whether both trill types are used in territorial encounters. Only one of the trill types was sung by males in response to playback, regardless on the trill type played to them. In an immediate response to playback, they increased the frequency of use of this trill, and also significantly increased the trill rate in comparison with spontaneous songs. This confirmed field observations, suggesting that this trill is important in male–male interactions. On the contrary, the use of the fastest, apparently more demanding, trill type actually decreased after the simulated territorial intrusion. We hypothesize that the latter one is more directed towards females, and that while performance of both trill types may reflect male quality, they are primarily used in different contexts.     

The GTPase RalA Regulates Different Steps of the Secretory Process in Pancreatic β-Cells

Background

RalA and RalB are multifuntional GTPases involved in a variety of cellular processes including proliferation, oncogenic transformation and membrane trafficking. Here we investigated the mechanisms leading to activation of Ral proteins in pancreatic β-cells and analyzed the impact on different steps of the insulin-secretory process.

Methodology/Principal Findings

We found that RalA is the predominant isoform expressed in pancreatic islets and insulin-secreting cell lines. Silencing of this GTPase in INS-1E cells by RNA interference led to a decrease in secretagogue-induced insulin release. Real-time measurements by fluorescence resonance energy transfer revealed that RalA activation in response to secretagogues occurs within 3–5 min and reaches a plateau after 10–15 min. The activation of the GTPase is triggered by increases in intracellular Ca²⁺ and cAMP and is prevented by the L-type voltage-gated Ca²⁺ channel blocker Nifedipine and by the protein kinase A inhibitor H89. Defective insulin release in cells lacking RalA is associated with a decrease in the secretory granules docked at the plasma membrane detected by Total Internal Reflection Fluorescence microscopy and with a strong impairment in Phospholipase D1 activation in response to secretagogues. RalA was found to be activated by RalGDS and to be severely hampered upon silencing of this GDP/GTP exchange factor. Accordingly, INS-1E cells lacking RalGDS displayed a reduction in hormone secretion induced by secretagogues and in the number of insulin-containing granules docked at the plasma membrane.

Conclusions/Significance

Taken together, our data indicate that RalA activation elicited by the exchange factor RalGDS in response to a rise in intracellular Ca²⁺ and cAMP controls hormone release from pancreatic β-cell by coordinating the execution of different events in the secretory pathway.     

Cardiomyopathy Mutations in the Tail of β-Cardiac Myosin Modify the Coiled-coil Structure and Affect Integration into Thick Filaments in Muscle Sarcomeres in Adult Cardiomyocytes

It is unclear why mutations in the filament-forming tail of myosin heavy chain (MHC) cause hypertrophic or dilated cardiomyopathy as these mutations should not directly affect contraction. To investigate this, we first investigated the impact of five hypertrophic cardiomyopathy-causing (N1327K, E1356K, R1382W, E1555K, and R1768K) and one dilated cardiomyopathy-causing (R1500W) tail mutations on their ability to incorporate into muscle sarcomeres in vivo. We used adenoviral delivery to express full-length wild type or mutant enhanced GFP-MHC in isolated adult cardiomyocytes. Three mutations (N1327K, E1356K, and E1555K) reduced enhanced GFP-MHC incorporation into muscle sarcomeres, whereas the remainder had no effect. No mutations significantly affected contraction. Fluorescence recovery after photobleaching showed that fluorescence recovery for the mutation that incorporated least well (N1327K) was significantly faster than that of WT with half-times of 25.1 ± 1.8 and 32.2 ± 2.5 min (mean ± S.E.), respectively. Next, we determined the effects of each mutation on the helical properties of wild type and seven mutant peptides (7, 11, or 15 heptads long) from the myosin tail by circular dichroism. R1382W and E1768K slightly increased the α-helical nature of peptides. The remaining mutations reduced α-helical content, with N1327K showing the greatest reduction. Only peptides containing residues 1301–1329 were highly α-helical suggesting that this region helps in initiation of coiled coil. These results suggest that small effects of mutations on helicity translate into a reduced ability to incorporate into sarcomeres, which may elicit compensatory hypertrophy.     

State Transition,Is It a Photochemical or Non-photochemical Process in Leaf in Response to Irradiance?

The response of steady-state fluorescence (Fs) to irradiance in apple (Malus pumila Mill. cv. Tengmu No.1/Malus hupehensis Rehd.) leaf increased and decreased at light levels below and above 400 mmol.m-2.s-1 photosynthetic photon flux density (PPFD), respectively, while the light-adapted maximal fluorescence (Fm') and minimal fluorescence (Fo') decreased constantly with the increasing PPFD, and the closure of photosystem Ⅱ reaction center (PSⅡ RC) increased continuously, reflected by the chlorophyll fluorescence parameter of (Fs-Fo')/(Fm'-Fo'). These facts indicated that decrease of Fs above 400 mmol.m-2.s-1 PPFD was not caused by closure of PSⅡ RC, but was mainly resulted from the process of light transfer from light-harvesting complexⅡ (LHCⅡ) to PSⅡ RC. In the presence of N-ethylmaleimide (NEM), an inhibitor of photosynthetic state transition, Fs kept on increasing in apple leaf at light levels from 400 to 700 mmol.m-2.s-1, which was the photosynthetic saturation irradiance of apple leaves. In addition, Fs still increased at light levels over 700 mmol.m-2.s-1 in apple leaf pre-treated with dithiothreitol (DTT), an inhibitor of xanthophyll cycle. These changes showed that state transition and xanthophyll cycle caused a decrease of Fs in apple leaf at light levels below and above the photosynthetic saturation irradiance, respectively. When apple leaf was pre-treated with NEM, the PSⅡ apparent rate of photochemical reaction (P-rate) and photochemical quenching (qP) decreased significantly in the light range of 600-800 mmol.m-2.s-1, but the non-photochemical quenching (qN) existed a small increase at 600-800 mmol.m-2.s-1 and a decrease above 800 mmol.m-2.s-1. These phenomena suggested that state transition was mainly a photochemical and a non-photochemical process in apple leaf responding to light lower and higher than photosynthetic saturation irradiance, respectively.     

Sesbania herbacea–Rhizobium huautlense Nodulation in Flooded Soils and Comparative Characterization of S. herbacea-Nodulating Rhizobia in Different Environments

Abstract The nodulation of S. herbacea was compared under flooded and non-flooded conditions in two different soils. One soil was from a flooded field in Sierra de Huautla, the native habitat of this legume, while the other soil was from a well-drained field in Cuernavaca, where rhizobia were found to nodulate the introduced S. herbacea plants. Nodulation of the plants was completely eliminated by flooding in the Cuernavaca soil, whereas nodules were obtained in the same soil under non-flooded conditions. In contrast, nodules were formed in Huautla soil under both flooded and non-flooded conditions. Most isolates, except isolate HS2, from Huautla soil and water were identified as R. huautlense by colony morphology, growth rate, PCR-RFLP of 16S rRNA genes, MLEE, cellular plasmid contents, and RFLP of nifH and nodDAB genes. Isolate HS2 was identified as Mesorhizobium sp. Isolates from Cuernavaca soil were different from R. huautlense in many aspects and were classified into five rDNA types within the genera Mesorhizobium, Rhizobium, and Sinorhizobium by PCR-RFLP of 16S rRNA genes. R. huautlense is a water Rhizobium species. Growth by denitrification under oxygen limitation or with ethanol was observed for R. huautlense bacteria but not for the isolates from Cuernavaca. In an interstrain nodulation competitive assay under both flooded and non-flooded conditions, R. huautlense strain S02 completely inhibited the nodulation of Mesorhizobium sp. Sn2, an isolate from Cuernavaca. From these results, we conclude that R. huautlense has the unique ability to nodulate S. herbacea not only in flooded soils, but in non-flooded soils as well. Received: 16 August 1999; Accepted: 28 December 1999; Online Publication: 13 June 2000     

Not Just a Sum? Identifying Different Types of Interplay between Constituents in Combined Interventions

Motivation

Experiments in which the effect of combined manipulations is compared with the effects of their pure constituents have received a great deal of attention. Examples include the study of combination therapies and the comparison of double and single knockout model organisms. Often the effect of the combined manipulation is not a mere addition of the effects of its constituents, with quite different forms of interplay between the constituents being possible. Yet, a well-formalized taxonomy of possible forms of interplay is lacking, let alone a statistical methodology to test for their presence in empirical data.

Results

Starting from a taxonomy of a broad range of forms of interplay between constituents of a combined manipulation, we propose a sound statistical hypothesis testing framework to test for the presence of each particular form of interplay. We illustrate the framework with analyses of public gene expression data on the combined treatment of dendritic cells with curdlan and GM-CSF and show that these lead to valuable insights into the mode of action of the constituent treatments and their combination.

Availability and Implementation

R code implementing the statistical testing procedure for microarray gene expression data is available as supplementary material. The data are available from the Gene Expression Omnibus with accession number GSE32986.     

Is Mating Different in Monogamous Species? The Midas Cichlid Fish as a Case Study

Monogamous species are typically sexually isomorphic, pair wellbefore spawning is imminent, take much time to pair, are discerningabout pairing, and appear to weigh multiple sources of informationabout species, sex, and quality of mate. The monogamous andpolychromatic Midas cichlid (Cichlasoma citrinellum) distinguishedbetween its own and a highly similar heterospecific behind aone-way mirror only when visual and chemical cues matched. Likewise,recognition of sex was hindered when interaction was precluded,even in the presence of chemical cues. Female choice of matewas most strongly influenced by the "normal, " primitive, colorand to a lesser degree by color of parents and siblings, makingit difficult to account for positive color-assortative matingin the field. Females also selected the largest and the mostaggressive males; size predicted a good defender of territory,and aggressiveness foretold effective protection of the young.Males, however, were not choosy. Pair formation features muchaggression between the large male and smaller female, and gold-coloredmorphs (G) dominate normal (N) ones. That made it difficultfor an N female to pair with a G male; using an N female thesame size as the G male, however, resulted in the usual proportionof successful pairings. I propose three testable models of paircompatibility: complementarity, parity, and maximum male aggressiveness.     

Cooperative breeding in oscine passerines: does sociality inhibit speciation?

Cooperative breeding in birds is much more prevalent than has been previously realized, occurring in 18.5% of oscine passerines known to have biparental care, and is the predominant social system of some ancient oscine clades. Cooperation is distributed unevenly in clades that contain both cooperative and pair breeders, and is usually confined to a few related genera in which it can be ubiquitous. Cooperative clades are species poor compared with pair-breeding clades, because pair breeders evolve migratory habits, speciate on oceanic islands and are more likely to have distributions spread across more than one biogeographic region. These differences reflect the increased capacity for colonization by pair breeders because their young disperse. Thus cooperative breeding has macroevolutionary consequences by restricting rates of speciation and macroecological implications by influencing the assembly of island and migrant faunas.     

Psychosocial Factors of Antenatal Anxiety and Depression in Pakistan: Is Social Support a Mediator?

Introduction

Pregnancy is generally viewed as a time of fulfillment and joy; however, for many women it can be a stressful event. In South Asia it is associated with cultural stigmas revolving around gender discrimination, abnormal births and genetic abnormalities.

Methodology

This cross-sectional study was done at four teaching hospitals in Lahore from February, 2014 to June, 2014. A total of 500 pregnant women seen at hospital obstetrics and gynecology departments were interviewed with a questionnaire consisting of three sections: demographics, the Hospital Anxiety and Depression Scale (HADS) and the Social Provisions Scale (SPS). Pearson’s chi-squared test, bivariate correlations and multiple linear regression were used to analyze associations between the independent variables and scores on the HADS and SPS.

Results

Mean age among the 500 respondents was 27.41 years (5.65). Anxiety levels in participants were categorized as normal (145 women, 29%), borderline (110, 22%) or anxious (245, 49%). Depression levels were categorized as normal (218 women, 43.6%), borderline (123, 24.6%) or depressed (159, 31.8%). Inferential analysis revealed that higher HADS scores were significantly associated with lower scores on the SPS, rural background, history of harassment, abortion, cesarean delivery and unplanned pregnancies (P < .05). Social support (SPS score) mediated the relationship between the total number of children, gender of previous children and HADS score. Women with more daughters were significantly more likely to score higher on the HADS and lower on the SPS, whereas higher numbers of sons were associated with the opposite trends in the scores (P < .05).

Conclusion

Because of the predominantly patriarchal sociocultural context in Pakistan, the predictors of antenatal anxiety and depression may differ from those in developed countries. We therefore suggest that interventions designed and implemented to reduce antenatal anxiety and depression should take into account these unique factors.     

Sulfur Metabolism in Plants: Are Trees Different?

Sulfur metabolite levels and sulfur metabolism have been studied in a significant number of herbaceous and woody plant species. However, only a limited number of datasets are comparable and can be used to identify similarities and differences between these two groups of plants. From these data, it appears that large differences in sulfur metabolite levels, as well as the genetic organization of sulfate assimilation and metabolism do not exist between herbaceous plants and trees. The general response of sulfur metabolism to internal and/or external stimuli, such as oxidative stress, seems to be conserved between the two groups of plants. Thus, it can be expected that, generally, the molecular mechanisms of regulation of sulfur metabolism will also be similar. However, significant differences have been found in fine tuning of the regulation of sulfur metabolism and in developmental regulation of sulfur metabolite levels. It seems that the homeostasis of sulfur metabolism in trees is more robust than in herbaceous plants and a greater change in conditions is necessary to initiate a response in trees. This view is consistent with the requirement for highly flexible defence strategies in woody plant species as a consequence of longevity. In addition, seasonal growth of perennial plants exerts changes in sulfur metabolite levels and regulation that currently are not understood. In this review, similarities and differences in sulfur metabolite levels, sulfur assimilation and its regulation are characterized and future areas of research are identified.     

Does Dormancy Increase Fitness of Bacterial Populations in Time-Varying Environments?

A simple family of models of a bacterial population in a time varying environment in which cells can transit between dormant and active states is constructed. It consists of a linear system of ordinary differential equations for active and dormant cells with time-dependent coefficients reflecting an environment which may be periodic or random, with alternate periods of low and high resource levels. The focus is on computing/estimating the dominant Lyapunov exponent, the fitness, and determining its dependence on various parameters and the two strategies—responsive and stochastic—by which organisms switch between dormant and active states. A responsive switcher responds to good and bad times by making timely and appropriate transitions while a stochastic switcher switches continuously without regard to the environmental state. The fitness of a responsive switcher is examined and compared with fitness of a stochastic switcher, and with the fitness of a dormancy-incapable organism. Analytical methods show that both switching strategists have higher fitness than a dormancy-incapable organism when good times are rare and that responsive switcher has higher fitness than stochastic switcher when good times are either rare or common. Numerical calculations show that stochastic switcher can be most fit when good times are neither too rare or too common. This research was supported by NSF Grant DMS 0414270, Department of Mathematics, Arizona State University, Tempe, AZ.     

Different Expression of Helicobacter pylori Gastritis in Children: Evidence for a Specific Pediatric Disease?

Background Infection with Helicobacter pylori causes active chronic gastritis. Once the infection is acquired, gastritis will persist for almost the rest of one's life. To date, very few data are available on H. pylori gastritis in relation to age. Therefore, we attempted to inestigate whether H. pylori gastritis in children exhibits features different from H. pylori gastritis in adults of two different age groups. Materials and Methods. Fifty consecutive children with a median age of 11 years (range, 3–18 years) were compared with two groups of 50 adult patients, one group with a median age of 43 (range, 19–56 years) and another group with a median age of 70 years (range, 59–86 years). All patients had H. pylori gastritis unrelated to active peptic ulcer disease. Two biopsy specimens were taken from the antrum and two from the corpus, and the following gastritis parameters were evaluated: degree and activity of gastritis, H. pylori colonization, replacement of foveolar epithelium by regenerative epithelium, mucous depletion, presence of atrophic gastritis with intestinal metaplasia, and presence of lymphoid follicles. Results. Degree and activity of gastritis, extent of H. pylori colonization, degree of replacement by regenerative epithelium, extent of mucous depletion, degree of atrophic gastritis with intestinal metaplasia, and the presence of lymphoid follicles in the antrum, as well as the presence of lymphoid follicles in the corpus differed significantly (chi-square test: p < .05). All these differences—except the once frequent occurrence of atrophic gastritis with intestinal metaplasia in adults—were attributable to a higher expression of these gastritis parameters in children. Conclusions. We conclude that H. pylori gastritis, particularly in the antrum, is more severely expressed in childhood. One reason for this might be a child-specific immune response to an infection with H. pylori. Alternatively, infection may represent a pediatric disease characterized by a nonatrophic, highly expressed form of gastritis, which changes its appearance once the host becomes adapted over time.