Laparoscopic splenectomy for hypersplenism secondary to liver cirrhosis and portal hypertension

Since the first laparoscopic splenectomy(LS)was reported in 1991,LS has become the gold standard for the removal of normal to moderately enlarged spleens in benign conditions.Compared with open splenectomy,fewer postsurgical complications and better postoperative recovery have been observed,but LS is contraindicated for hypersplenism secondary to liver cirrhosis in many institutions owing to technical difficulties associated with splenomegaly,well-developed collateral circulation,and increased risk of bleeding.With the improvements of laparoscopic technique,the concept is changing.This article aims to give an overview of the latest development in laparoscopic splenectomy for hypersplenism secondary to liver cirrhosis and portal hypertension.Despite a lack of randomized controlled trial,the publications obtained have shown that with meticulous surgical techniques and advanced instruments,LS is a technically feasible,safe,and effective procedure for hypersplenism secondary to cirrhosis and portal hypertension and contributes to decreased blood loss,shorter hospital stay,and less impairment of liver function.It is recommended that the dilated short gastric vessels and other enlarged collateral circulation surrounding the spleen be divided with the LigaSure vessel sealing equipment,and the splenic artery and vein be transected en bloc with the application of the endovascular stapler.To support the clinical evidence,further randomized controlled trials about this topic are necessary.

Fetal and neonatal programming of postnatal growth and feed efficiency in swine

Maternal undernutrition or overnutrition during pregnancy alters organ structure, impairs prenatal and neonatal growth and development, and reduces feed efficiency for lean tissue gains in pigs. These adverse effects may be carried over to the next generation or beyond. This phenomenon of the transgenerational impacts is known as fetal programming, which is mediated by stable and heritable alterations of gene expression through covalent modifications of DNA and histones without changes in DNA sequences(namely, epigenetics). The mechanisms responsible for the epigenetic regulation of protein expression and functions include chromatin remodeling; DNA methylation(occurring at the 5′-position of cytosine residues within CpG dinucleotides); and histone modifications(acetylation, methylation, phosphorylation, and ubiquitination). Like maternal malnutrition, undernutrition during the neonatal period also reduces growth performance and feed efficiency(weight gain:feed intake; also known as weightgain efficiency) in postweaning pigs by 5–10%, thereby increasing the days necessary to reach the market bodyweight. Supplementing functional amino acids(e.g., arginine and glutamine) and vitamins(e.g., folate) play a key role in activating the mammalian target of rapamycin signaling and regulating the provision of methyl donors for DNA and protein methylation. Therefore, these nutrients are beneficial for the dietary treatment of metabolic disorders in offspring with intrauterine growth restriction or neonatal malnutrition. The mechanism-based strategies hold great promise for the improvement of the efficiency of pork production and the sustainability of the global swine industry.

Endoplasmic reticulum stress-induced apoptosis in intestinal epithelial cells:a feed-back regulation by mechanistic target of rapamycin complex 1(mTORC1)

Background: Endoplasmic reticulum(ER) stress is associated with multiple pathological processes of intestinal diseases. Despite a critical role of mechanistic target of rapamycin complex 1(m TORC1) in regulating cellular stress response, the crosstalk between m TORC1 and ER stress signaling and its contribution to the intestinal barrier function is unknown.Results: In the present study, we showed that intestinal epithelial cells(IEC-6) incubated with tunicamycin led to caspase-3-dependent apoptotic cell death. The induction of cell death was accompanied by activation of unfolded protein response as evidenced by increased protein levels for Bi P, p-IRE1α, p-e IF2α, p-JNK, and CHOP. Further study demonstrated that tunicamycin-induced cell death was enhanced by rapamycin, a specific inhibitor of m TORC1.Consistently, tunicamycin decreased transepithelial electrical resistance(TEER) and increased permeability of the cells. These effects of tunicamycin were exacerbated by m TORC1 inhibitor.Conclusions: Taken together, the data presented here identified a previously unknown crosstalk between an unfold protein response and m TORC1 signaling in the intestinal epithelium. This feed-back loop regulation on ER stress signaling by m TORC1 is critical for cell survival and intestinal permeability in epithelial cells.

New strategy during complicated open appendectomy: Convert open operation to laparoscopy

AIM: To introduce a new strategy during complicated open appendectomy - converting open operation to laparoscopy.

Coupling Enhancement of a Flexible BiFeO_(3) Film-Based Nanogenerator for Simultaneously Scavenging Light and Vibration Energies

Coupled nanogenerators have been a research hotspot due to their ability to harvest a variety of forms of energy such as light,mechanical and thermal energy and achieve a stable direct current output.Ferroelectric films are frequently investigated for photovoltaic applications due to their unique photovoltaic properties and bandgap-independent photovoltage,while the flexoelectric effect is an electromechanical property commonly found in solid dielectrics.Here,we effectively construct a new form of coupled nanogenerator based on a flexible BiFeO_(3) ferroelectric film that combines both flexoelectric and photovoltaic effects to successfully harvest both light and vibration energies.This device converts an alternating current into a direct current and achieves a 6.2% charge enhancement and a 19.3%energy enhancement to achieve a multi-dimensional"1+1>2"coupling enhancement in terms of current,charge and energy.This work proposes a new approach to the coupling of multiple energy harvesting mechanisms in ferroelectric nanogenerators and provides a new strategy to enhance the transduction efficiency of flexible functional devices.

Legionella pneumonia complicated with rhabdomyolysis and acute kidney injury diagnosed by metagenomic nextgeneration sequencing: a case report

The triad of Legionella pneumonia,rhabdomyolysis,and acute kidney injury(AKI)is uncommon but can be devastating.[1]It is vital to recognize Legionella species early as a potential cause of pneumonia.Legionella infection remains underdiagnosed because of the nonspecific nature of clinical features and the shortcomings of routinely available diagnostic tests.[2]Metagenomic next-generation sequencing(mNGS)is a culture-free and hypothesis-free diagnostic method that can rapidly identify almost all known pathogens in a sample.[3]Here,we present a successfully cured case of rhabdomyolysis and AKI caused by Legionella pneumophila with etiologic diagnosis aided by the use of mNGS.

Row Spacing Affects Biomass Yield and Composition of Kenaf (<i>Hibiscus cannabinus</i>L.) as a Lignocellulosic Feedstock for Bioenergy

Kenaf (Hibiscus cannabinus L.) is a warm-season annual. Kenaf fibers are commonly used for paper pulp and cordage, but it is also a promising lignocellulosic feedstock for bioenergy production, although optimum plant density for biomass production has not been determined for the northern region of the USA. The objective of this study was to determine the best plant density and row spacing of kenaf to maximize biomass yield and chemical composition for biofuel conversion. The experiments were conducted at Fargo and Prosper, ND, in 2010 and 2011. The experiment was a randomized complete block design with a split-plot arrangement where the main plot was tworowspacings (30 and60 cm) and the sub-plot fourplant densities (32, 16, 8, and 4 plants·m-2). Row spacing had a significant effect on both biomass and biofuel yield. Narrower rows had higher biomass and biofuel yield. Maximum biomass and estimated biofuel yield was obtained with the two highest plant densities of 16 and 32 plants·m-2 and fluctuated between 9.45 and 10.22 Mg·ha-1 and 1354 and1464 L·ha-1, respectively. Stem diameter increased with a decrease in plant density. Chemical composition varied with plant density;glucan (27%) and xylan (9.8%) content were lower at the lowest plant density. Ash content was not different among plant densities but it is interesting to mention the very low ash content of kenaf (0.15%). According to the results of this study, it is recommended to plant kenaf at 30-cm rows with a plant density of 16 to 32 plants·m-2 to maximize biomass yield. Kenaf has a tremendous potential as a cellulosic feedstock for biofuel and green chemicals in the Northern Great Plains because of high biomass yield and low ash content.

Dihydroartemisinin ameliorates innate inflammatory response induced by Streptococcus suis-derived muramidase-released protein via inactivation of TLR4-dependent NF-kB signaling

Muramidase-released protein(MRP)is now being recognized as a critical indicator of the virulence and pathogenicity of Streptococcus suis(S.suis).However,the identification of viable therapeutics for S.suis infection was hindered by the absence of an explicit mechanism for MRP-actuated inflammation.Dihydroartemisinin(DhA)is an artemisinin derivative with potential anti-inflammatory activity.The modulatory effect of DhA on the inflammatory response mediated by the virulence factor MRP remains obscure.This research aimed to identify the signaling mechanism by which MRP triggers the innate immune response in mouse spleen and cultured macrophages.With the candidate mechanism in mind,we investigated DhA for its ability to dampen the pro-inflammatory response induced by MRP.The innate immune response in mice was drastically triggered by MRP,manifesting as splenic and systemic inflammation with splenomegaly,immune cell infiltration,and an elevation in pro-inflammatory cytokines.A crucial role for Toll-like receptor 4(TLR4)in coordinating the MRP-mediated inflammatory response via nuclear factor-kappa B(NF-kB)activation was revealed by TLR4 blockade.In addition,NFkB-dependent transducer and activator of transcription 3(STAT3)and mitogen-activated protein kinases(MAPKs)activation was required for the inflammatory signal transduction engendered by MRP.Intriguingly,we observed an alleviation effect of DhA on the MRP-induced immune response,which referred to the suppression of TLR4-mediated actuation of NF-kB-STAT3/MAPK cascades.The inflammatory response elicited by MRP is relevant to TLR4-dependent NF-kB activation,followed by an increase in the activity of STAT3 or MAPKs.DhA mitigates the inflammation process induced by MRP via blocking the TLR4 cascade,highlighting the therapeutic potential of DhA in targeting S.suis infection diseases.

(根本)说一切有部长阿含的内容与结构

最近一些年来,由于阿富汗地区的政局动荡,各种印度语言的大批佛教写本从大犍陀罗地区(Great Gandhara)来到了西方的珍本书籍市场。遗憾的是,这些写本的绝大多数都是残片,并且我们也不知道它们确切的发现地或者其原始存放地——(石窟)寺、塔婆等。

Ti_(3)C_(2)-assisted construction of Z-scheme MIL-88A(Fe)/Ti_(3)C_(2)/RF heterojunction:Multifunctional photocatalysis-in-situ-self-Fenton catalyst

The applicability of the conventional Fenton reaction is limited due to several factors,including the high cost and slow redox cycle of Fe^(3+)/Fe^(2+),the requirement for harsh acidic conditions,and the insufficient presence of hydroxyl radicals for the ring-opening reaction.The combination of photocatalysis and Fenton technology to create a photocatalysis-in-situ-self-Fenton(PISF)system is a viable approach for addressing the inherent limitations of conventional Fenton reactions.Herein,a multifunctional PISF system,MIL-88A(Fe)/Ti_(3)C_(2) MXene/resorcinol-formaldehyde(MIL-88A(Fe)/Ti_(3)C_(2)/RF,MTR)Z-scheme heterojunction,was designed and constructed for degradating organics and inactivating bacteria.With the assistance of Ti_(3)C_(2),the degradation rate of TC by MTR catalyst was 4.8 times that of MIL-88A(Fe)/RF catalyst under visible light irradiation.Meanwhile,good degradation performance was maintained after 5 cycling tests.The remarkable TC removal efficiency(97.4%)and durability were attributed to the synergistic effect of the photocatalytic reaction and Fenton reaction.The photoinduced holes(h^(+))assist hydroxyl radicals(·OH)generated by the Fenton reaction for deeply mineralizing TC.The degradation intermediates,potential degradation pathways,and intermediates toxicity were comprehensively investigated to gain a deeper understanding of the catalytic process.Moreover,under visible light irradiation,the MTR killed 97.8%of E.coli and 94.9%of S.aureus within 120 min,demonstrating good antibacterial activity.This work provides a novel strategy to design PISF catalysts for environmental remediation.

LIM-domain-only 4(LMO4)enhances CD8^(+)T-cell stemness and tumor rejection by boosting IL-21-STAT3 signaling

High frequencies of stem-like memory T cells in infusion products correlate with superior patient outcomes across multiple T cell therapy trials.Herein,we analyzed a published CRISPR activation screening to identify transcriptional regulators that could be harnessed to augment stem-like behavior in CD8^(+)T cells.Using IFN-γproduction as a proxy for CD8^(+)T cell terminal differentiation,LMO4 emerged among the top hits inhibiting the development of effectors cells.Consistently,we found that Lmo4 was downregulated upon CD8^(+)T cell activation but maintained under culture conditions facilitating the formation of stem-like T cells.By employing a synthetic biology approach to ectopically express LMO4 in antitumor CD8^(+)T cells,we enabled selective expansion and enhanced persistence of transduced cells,while limiting their terminal differentiation and senescence.LMO4 overexpression promoted transcriptional programs regulating stemness,increasing the numbers of stem-like CD8^(+)memory T cells and enhancing their polyfunctionality and recall capacity.When tested in syngeneic and xenograft tumor models,LMO4 overexpression boosted CD8^(+)T cell antitumor immunity,resulting in enhanced tumor regression.Rather than directly modulating gene transcription,LMO4 bound to JAK1 and potentiated STAT3 signaling in response to IL-21,inducing the expression of target genes(Tcf7,Socs3,Junb,and Zfp36)crucial for memory responses.CRISPR/Cas9-deletion of Stat3 nullified the enhanced memory signature conferred by LMO4,thereby abrogating the therapeutic benefit of LMO4 overexpression.These results establish LMO4 overexpression as an effective strategy to boost CD8^(+)T cell stemness,providing a new synthetic biology tool to bolster the efficacy of T cell-based immunotherapies.

Enhancing memristor performance with 2D SnO_(x)/SnS_(2) heterostructure forneuromorphic computing

Layered metal dichalcogenides (LMDs) neuromorphic memristor devices offer a promising alternative toconventional von Neumann architectures, addressing speedand energy efficiency constraints. However, challenges remainin controlling resistive switching and operating voltage incrystalline LMD memristors due to environmental stabilization issues, which hinder neural network hardware development. Herein, we introduce an optimization method formemristor operation by controlling oxidation through ozonetreatment, creating a SnO_(x)/SnS_(2) resistive layer. These optimized memristors demonstrate low switching voltages (~1 V),rapid switching speeds (~20 ns), high switching ratios (10^(2)),and the ability to emulate synaptic weight plasticity. Crosssectional transmission electron microscopy and energy-dispersive X-ray spectroscopy identified defects and Ti conductive filaments in the resistive switching layer, contributingto uniform switching and minimized operating variation. Thedevice achieved 90% accuracy in MNIST handwritten recognition, and hardware-based image convolution was successfully implemented, showcasing the potential of SnO_(x)/SnS_(2)memristors for neuromorphic applications.

FOXO3-engineered human mesenchymal progenitor cells efficiently promote cardiac repair after myocardial infarction

Dear Editor,Myocardial infarction(MI)is the irreversible cardiomyocyte death resulting from prolonged oxygen deprivation due to obstructed blood supply(ischemia),leading to contractile dysfunction and cardiac remodeling.In recent decades,stem cell transplantation has been extensively investigated for the repair of injured heart in animal studies and clinical trials(Kanelidis et al.,2017;Gyongyosi et al.,2018).

Glycine represses endoplasmic reticulum stress-related apoptosis and improves intestinal barrier by activating mammalian target of rapamycin complex 1 signaling

Endoplasmic reticulum(ER)stress has been associated with the dysfunction of intestinal barrier in humans and animals.We have previously shown that oral administration of glycine to suckling-piglets improves ER stress-related intestinal mucosal barrier impairment and jejunal epithelial apoptosis.However,the underlying mechanism remains unknown.In this study,the protective effect and the mechanism of glycine on apoptosis and dysfunction in intestinal barrier induced by brefeldin A(BFA),an ER stress inducer,was explored in porcine intestinal epithelial cells(IPEC-1).The results showed that BFA treatment led to enhanced apoptosis and upregulation of proteins involved in ER stress signaling,including inositol-requiring enzyme 1a(IRE1a),activating transcription factor 6a(ATF6a),c-Jun N-terminal kinase(JNK),and C/EBP-homologous protein(CHOP).In addition,BFA induced a dysfunction in intestinal epithelial barrier,as evidenced by the increased paracellular permeability,decreased transepithelial electrical resistance(TEER),and reduced abundance of tight junction proteins(occludin,claudin-1,zonula occludens[ZO]-1,and ZO-2).These alterations triggered by BFA were significantly abolished by glycine treatment(P<0.05),indicating a protective effect of glycine on barrier function impaired by ER stress.Importantly,we found that the regulatory effect of glycine on intestinal permeability,proteins implicated in ER stress and apoptosis,as well as the morphological alterations of the ER were reversed by rapamycin.In summary,our results indicated that glycine alleviates ER stress-induced apoptosis and intestinal barrier dysfunction in IPEC-1 cells in a mammalian target of rapamycin complex 1(mTORC1)-dependent manner.The data provides in vitro evidence and a mechanism for the protective effect of glycine against the disruption of intestinal barrier integrity induced by ER stress.

A multifunctional optical-thermal logic gate sensor array based on ferroelectric BiFeO_(3) thin films

The growing need to process a diverse range of data has ignited effort in developing new multifunctional logic gate devices.In this article,we report a new form of all-in-one logic gate system that exploits the photoresponsivity of a self-powered multifunctional BiFeO_(3)(BFO)sensor material.The BFO sensor can not only detect both light intensity and temperature,but it can also execute three common logic gates of“AND”,“OR”,and“NOT”by converting optical and thermal inputs into electrical output.The diverse functionality of the BFO logic gate sensor array utilizes the unique light-and temperaturecontrolled energy band structure and carrier behavior of the BFO material.To demonstrate the potential,a 3×3 logic gate sensor matrix is developed,which successfully detected light and temperature distributions,and accurately produced the three basic logic gate operations.This work provides a new route to construct highly integrated multifunctional electronic devices for the advancement of large sensing,communication,and computing operations.

Oligomer saccharide reduction during dilute acid pretreatment co-catalyzed with Lewis acids on corn stover biomass

The dilute sulfuric acid pretreatment of lignocellulosic biomass is a well understood process that significantly enhances the yield of glucose after enzymatic saccharification.The goal of this research was to perform a systematic study to evaluate the yield of fermentable sugars during dilute sulfuric acid pretreatment that is co-catalyzed with the transition metal Lewis acid salts:AlCl_(3),FeCl_(2),FeCl_(3),and La(OTf)_(3).All Lewis acids apart from FeCl_(2)reduced the presence of xylo-oligomers by a large margin when compared to the non-co-catalyzed control sample pretreatments.The presence of these xylo-oligomers acts as inhibitors during enzymatic saccaharification step.The Lewis acids AlCl_(3),FeCl_(3),and La(OTf)_(3)were also able to marginally increase the overall enzymatic digestibility specifically for corn stover pretreated at 160℃with 10 mM of Lewis acids.The hard Lewis acid such as AlCl3 increased the formation inhibitory products such as furfural and 5-hydroxymethylfurfural(HMF).There was good correlation between reduction of xylo-oligomers and increased concentration furfural with increase in Lewis acid hardness.

Pretreatment and enzymatic hydrolysis of sunflower hulls for fermentable sugar production

Sunflower is a widely adapted crop and can be grown in every temperature region.In the U.S.,two million acres were cultivated with sunflowers in 2009.During industrial processing,large quantities of hulls are obtained as a waste product from the dehulling process.This study focused on converting the sunflower hulls into fermentable sugars by dilute acid pretreatment and enzymatic hydrolysis.Raw sunflower hulls are composed ofβ-glucan(34%±1.1%),lignin(25%±0.95%),xylan and arabinan(27%±1.56%),extractives(13%±2.5%)and traces of ash.Sunflower hulls were first subjected to pretreatment by varying three independent factors:1)acid concentration(0.5%-2%);2)reaction temperatures(140-160℃);3)reaction time(10-30 min).Slurry samples obtained after pretreatment were separated into liquid and solid fractions.Liquid fractions were analyzed for monomeric and oligomeric sugars and inhibitor products by High Pressure Liquid Chromatography(HPLC).Enzymatic saccharification was then performed on pretreated solid fractions to convert remaining cellulose(β-glucan)into fermentable sugars.The results showed an increase in acid concentration and reaction temperature gave high xylose yield in the liquid fraction.However,an increase in reaction time resulted in degradation of xylose into furfural.A quadratic model for xylose yield was formulated based on the experimental results.The maximum xylose yield predicted by the model was 62%at 158℃for 20 min at 1.75%acid concentration.The maximumβ-glucan digestibility of the enzymatic saccharification was 53.5%at 160℃for 30 min at 2%acid concentration.

Hydroxyproline alleviates 4-hydroxy-2-nonenal-induced DNA damage and apoptosis in porcine intestinal epithelial cells

Oxidative stress has been confirmed in relation to intestinal mucosa damage and multiple bowel diseases.Hydroxyproline (Hyp) is an imino acid abundant in sow's milk. Compelling evidence has beengathered showing the potential antioxidative properties of Hyp. However, the role and mechanism ofHyp in porcine intestinal epithelial cells in response to oxidative stress remains unknown. In this study,small intestinal epithelial cell lines of piglets (IPEC-1) were used to evaluate the protective effects of Hypon 4-hydroxy-2-nonenal (4-HNE)-induced oxidative DNA damage and apoptosis. IPEC-1 pretreated with0.5 to 5 mmol/L Hyp were exposed to 4-HNE (40 mmol/L) in the presence or absence of Hyp. Thereafter,the cells were subjected to apoptosis detection by Hoechst staining, flow cytometry, and Western blot orDNA damage analysis by comet assay, immunofluorescence, and reverse-transcription quantitative PCR(RT-qPCR). Cell apoptosis and the upregulation of cleaved-caspase-3 induced by 4-HNE (40 mmol/L) wereinhibited by 5 mmol/L of Hyp. In addition, 5 mmol/L Hyp attenuated 4-HNE-induced reactive oxygenspecies (ROS) accumulation, glutathione (GSH) deprivation and DNA damage. The elevation in transcriptionof GADD45a (growth arrest and DNA-damage-inducible protein 45 alpha) and GADD45b(growth arrest and DNA-damage-inducible protein 45 beta), as well as the phosphorylation of H2AX(H2A histone family, member X), p38 MAPK (mitogen-activated protein kinase), and JNK (c-Jun N-terminalkinase) in cells treated with 4-HNE were alleviated by 5 mmol/L Hyp. Furthermore, Hyp supplementationincreased the protein abundance of Krüppel like factor 4 (KLF4) in cells exposed to 4-HNE.Suppression of KLF4 expression by kenpaulone impeded the resistance of Hyp-treated cells to DNAdamage and apoptosis induced by 4-HNE. Collectively, our results indicated that Hyp serves to protectagainst 4-HNE-induced apoptosis and DNA damage in IPEC-1 cells, which is partially pertinent with theenhanced expression of KLF4. Our data provides an updated explanation for the nutritional values ofHyp-containing animal products.

Multieffect Coupled Nanogenerators

With the advent of diverse electronics,the available energy may be light,thermal,and mechanical energies.Multieffect coupled nanogenerators(NGs)exhibit strong ability to harvest ambient energy by integrating various effects comprising piezoelectricity,pyroelectricity,thermoelectricity,optoelectricity,and triboelectricity into a standalone device.Interaction of multitype effects can promote energy harvesting and conversion by modulating charge carriers’behaviour.Multieffect coupled NGs stand for a vital group of energy harvesters,supporting the advances of an electronic device and promoting the resolution of energy crisis.The matchless versatility and high reliability of multieffect coupled NGs make them main candidates for integration in complicated arrays of the electronic device.Multieffect coupled NGs can also be employed as a variety of self-powered sensors due to their rapid response,high accuracy,and high responsivity.This article reviews the latest achievements of multieffect coupled NGs.Fundamentals mainly including basic theory and materials of interest are covered.Advanced device design and output characteristics are introduced.Potential applications are described,and future development is discussed.

Lineage relationship of CD8^＋ T cell subsets is revealed by progressive changes in the epigenetic landscape

To better elucidate epigenetic mechanisms that correlate with the dynamic gene expression program observed upon T-cell differentiation, we investigated the genomic landscape of histone modifications in naive and memory CD8＋ T cells. Using a ChlP-Seq approach coupled with global gene expression profiling, we generated genome-wide histone H3 lysine 4 （H3K4me3） and H3 lysine 27 （H3K27me3） trimethylation maps in naive, T memory stem cells, central memory cells, and effector memory cells in order to gain insight into how histone architecture is remodeled during T cell differentiation. We show that H3K4me3 histone modifications are associated with activation of genes, while H3K27me3 is negatively correlated with gene expression at canonical loci and enhancers associated with T-cell metabolism, effector function, and memory. Our results also reveal histone modifications and gene expression signatures that distinguish the recently identified T memory stem cells from other CD8＋ T-cell subsets. Taken together, our results suggest that CD8＋ lymphocytes undergo chromatin remodeling in a progressive fashion. These findings have major implications for our understanding of peripheral T-cell ontogeny and the formation of immunological memory.