T cell-derived interleukin-22 drives the expression of CD155 by cancer cells to suppress NK cell function and promote metastasis.

Although T cells can exert potent anti-tumor immunity, a subset of T helper (Th) cells producing interleukin-22 (IL-22) in breast and lung tumors is linked to dismal patient outcome. Here, we examined the mechanisms whereby these T cells contribute to disease. In murine models of lung and breast cancer, constitutional and T cell-specific deletion of Il22 reduced metastases without affecting primary tumor growth. Deletion of the IL-22 receptor on cancer cells decreases metastasis to a degree similar to that seen in IL-22-deficient mice. IL-22 induced high expression of CD155, which bound to the activating receptor CD226 on NK cells. Excessive activation led to decreased amounts of CD226 and functionally impaired NK cells, which elevated the metastatic burden. IL-22 signaling was also associated with CD155 expression in human datasets and with poor patient outcomes. Taken together, our findings reveal an immunosuppressive circuit activated by T cell-derived IL-22 that promotes lung metastasis.

The Effectiveness of Publicly Available Web-Based Interventions in Promoting Health App Use, Digital Health Literacy, and Media Literacy: Pre-Post Evaluation Study.

BACKGROUND: According to the World Health Organization, implementing mobile health (mHealth) technologies can increase access to quality health services worldwide. mHealth apps for smartphones, also known as health apps, are a central component of mHealth, and they are already used in diverse medical contexts. To benefit from health apps, potential users need specific skills that enable them to use such apps in a responsible and constructive manner. OBJECTIVE: This study aimed to evaluate the effectiveness of the free and widely used web-based intervention, The APPocalypse?. Besides providing knowledge about health apps, the web-based intervention was designed to promote digital health and media literacy by teaching skills that enable users to distinguish between trustworthy and less trustworthy health apps. It was hypothesized that after completing the web-based intervention, participants' knowledge in the domain of health apps, their digital health literacy, and their media literacy would be higher than it was before completing the web-based intervention. METHODS: The study was divided into 3 parts. During part 1, participants (n=365; 181 female, 181 male, and 3 diverse; mean age 17.74, SD 1.391 years) provided demographic information and answered the pre- and postmeasurements. The measurements included questionnaires about participants' knowledge in the domain of health apps, digital health literacy, and media literacy. During part 2, participants had 1 week to complete the web-based intervention. During part 3, participants answered the pre- and postmeasurements again. Furthermore, they answered educational quality and user experience questionnaires. Bayesian paired samples 2-tailed t tests were conducted to test the hypotheses. RESULTS: Overall, the results support the hypotheses. After completing the web-based intervention, participants demonstrated more elaborate knowledge in the domain of health apps. Specifically, they displayed higher competencies in the domains of subjective (Bayes factor10 [BF10]=1.475×1079; effect size δ=-1.327) and objective health app knowledge (BF10=8.162×1080; effect size δ=-1.350). Furthermore, participants demonstrated higher digital health literacy. Specifically, they displayed higher competencies in the domains of information appraisal (BF10=3.413×1043; effect size δ=-0.870), information searching (BF10=3.324×1023; effect size δ=-0.604), evaluating reliability (BF10=3.081×1035; effect size δ=-0.766), and determining relevance (BF10=3.451×1024; effect size δ=-0.618). Regarding media literacy, the results were mixed. Participants displayed higher competencies in the domain of technology literacy beliefs (BF10=1.533×1021; effect size δ=-0.570). In the domain of technology control beliefs, their competencies did not seem to improve (BF10=0.109; effect size δ=-0.058). In comparison to relevant benchmarks, the web-based intervention offers exceptional educational quality and a superior user experience. CONCLUSIONS: The free web-based intervention The APPocalypse? might promote the constructive use of health apps, digital health literacy, and media literacy. Therefore, it may contribute to achieving the health-related United Nations Sustainable Development Goals.

The Development and Evaluation of an e-Learning Course That Promotes Digital Health Literacy in School-age Children: Pre-Post Measurement Study.

BACKGROUND: Experts agree that the promotion of (digital) health literacy should be an integral part of the school curriculum. However, promoting (digital) health literacy within the German school system is difficult because (digital) health education is not a mandatory school subject in all the German states. Therefore, experts suggest that (digital) health literacy could be addressed as part of the mandatory framework for digital education and digital literacy in schools developed by the German Conference on Education Ministries and Cultural Affairs (Kultusministerkonferenz). OBJECTIVE: The goal of this study was to evaluate a newly developed e-learning course that was designed to improve (digital) health literacy in school-age children and concurrently to teach skills specified in the mandatory framework for digital education and digital literacy in schools. It was hypothesized that participants' health literacy and digital health literacy levels would be higher after completing the e-learning course than they were before doing the course. Furthermore, it was hypothesized that after completing the e-learning course, participants' subjective and objective knowledge in the domain of (digital) health literacy would be higher than it was before doing the course. METHODS: The pre-post measurement study was conducted online. After participants (N=323) gave their informed consent to participate in the study, they provided demographic information and answered all measures (premeasurement). Following this, participants had 7 days to complete the e-learning course. After finishing the e-learning course, participants answered all the measures again (postmeasurement). RESULTS: To test the hypotheses, Bayesian paired samples t tests (1-sided) were conducted. After completing the e-learning course, participants showed higher health literacy levels. Specifically, they showed higher competency levels in the domains of theoretical knowledge (Bayes factor [BF]-0=676,000; δ=-0.316), practical knowledge (BF-0=92,300; δ=-0.294), critical thinking (BF-0=7.42e+13; δ=-0.482), self-awareness (BF-0=11,500,000; δ=-0.345), and citizenship (BF-0=266,000; δ=-0.306). Furthermore, participants achieved higher digital health literacy levels. Specifically, they achieved higher competency levels in the domains of information searching (BF-0=2.339; δ=-0.135), evaluating reliability (BF-0=2.03e+11; δ=-0.434), and determining relevance (BF-0=316,000; δ=-0.308). Moreover, participants demonstrated higher subjective (BF-0=3.58e+82; δ=-1.515) and objective knowledge (BF-0=3.82e+97; δ=-1.758) in the domain of (digital) health literacy. CONCLUSIONS: The newly designed e-learning course provides an easy way for schools and teachers from all German states to integrate (digital) health literacy education into their school curriculums and lessons. The evaluated course is especially attractive because it was designed to improve (digital) health literacy and at the same time to teach skills specified in the mandatory framework for digital education and digital literacy in schools developed by the German Conference on Education Ministries and Cultural Affairs (Kultusministerkonferenz).

Novel Poxin Stable cGAMP-Derivatives Are Remarkable STING Agonists.

2',3'-cGAMP is a cyclic A- and G-containing dinucleotide second messenger, which is formed upon cellular recognition of foreign cytosolic DNA as part of the innate immune response. The molecule binds to the adaptor protein STING, which induces an immune response characterized by the production of type I interferons and cytokines. The development of STING-binding molecules with both agonistic as well as antagonistic properties is currently of tremendous interest to induce or enhance antitumor or antiviral immunity on the one hand, or to treat autoimmune diseases on the other hand. To escape the host innate immune recognition, some viruses encode poxin endonucleases that cleave 2',3'-cGAMP. Here we report that dideoxy-2',3'-cGAMP (1) and analogs thereof, which lack the secondary ribose-OH groups, form a group of poxin-stable STING agonists. Despite their reduced affinity to STING, particularly the compound constructed from two A nucleosides, dideoxy-2',3'-cAAMP (2), features an unusually high antitumor response in mice.

Recruitment of the cytoplasmic adaptor Grb2 to surface IgG and IgE provides antigen receptor-intrinsic costimulation to class-switched B cells.

The improved antibody responses of class-switched memory B cells depend on enhanced signaling from their B cell antigen receptors (BCRs). However, BCRs on both naive and antigen-experienced B cells use the canonical immunoglobulin-associated alpha and beta-protein signaling subunits. Here we identified a BCR isotype-specific signal-amplification mechanism. Whereas immunoglobulin M (IgM)-containing BCRs initiated intracellular signals exclusively through immunoglobulin-associated alpha- and beta-proteins, IgG- and IgE-containing BCRs also used a conserved tyrosine residue in the cytoplasmic segments of immunoglobulin heavy chains. When phosphorylated, this tyrosine recruited the adaptor Grb2, resulting in sustained protein kinase activation and prolonged generation of second messengers, which together culminated in enhanced B cell proliferation. Hence, membrane-bound IgG and IgE exert antigen recognition as well as costimulatory functions, thereby rendering memory B cells less dependent on T cell help.

Systemic but not MDSC-specific IRF4 deficiency promotes an immunosuppressed tumor microenvironment in a murine pancreatic cancer model.

Pancreatic ductal adenocarcinoma is characterized by a strong immunosuppressive network with a dense infiltration of myeloid cells including myeloid-derived suppressor cells (MDSC). Two distinct populations of MDSC have been defined: polymorphonuclear MDSC (PMN-MDSC) and monocytic MDSC (M-MDSC). Several factors influence the development and function of MDSC including the transcription factor interferon regulatory factor 4 (IRF4). Here, we show that IRF4 deficiency accelerates tumor growth and reduces survival, accompanied with a dense tumor infiltration with PMN-MDSC and reduced numbers of CD8+ T cells. As IRF4 has been described to modulate myeloid cell development and function, particularly of PMN-MDSC, we analyzed its role using MDSC-specific IRF4 knockout mice with the Ly6G or LysM knock-in allele expressing Cre recombinase and Irf4flox. In GM-CSF-driven bone marrow cultures, IRF4 deficiency increased the frequency of MDSC-like cells with a strong T cell suppressive capacity. Myeloid (LysM)-specific depletion of IRF4 led to increased tumor weight and a moderate splenic M-MDSC expansion in tumor-bearing mice. PMN cell (Ly6G)-specific depletion of IRF4, however, did not influence tumor progression or MDSC accumulation in vivo in accordance with our finding that IRF4 is not expressed in PMN-MDSC. This study demonstrates a critical role of IRF4 in the generation of an immunosuppressive tumor microenvironment in pancreatic cancer, which is independent of IRF4 expression in PMN-MDSC.

Inhibition of Cyclin-Dependent Kinase 5: A Strategy to Improve Sorafenib Response in Hepatocellular Carcinoma Therapy.

Therapeutic options for patients with advanced-stage hepatocellular carcinoma (HCC) are very limited. The only approved first-line treatment is the multi-tyrosine kinase inhibitor sorafenib, which shows low response rates and severe side effects. In particular, the compensatory activation of growth factor receptors leads to chemoresistance and limits the clinical impact of sorafenib. However, combination approaches to improve sorafenib have failed. Here we investigate the inhibition of cyclin-dependent kinase 5 (Cdk5) as a promising combination strategy to improve sorafenib response in HCC. Combination of sorafenib with Cdk5 inhibition (genetic knockdown by short hairpin RNA or CRISPR/Cas9 and pharmacologic inhibition) synergistically impaired HCC progression in vitro and in vivo by inhibiting both tumor cell proliferation and migration. Importantly, these effects were mediated by a mechanism for Cdk5: A liquid chromatography-tandem mass spectrometry-based proteomic approach revealed that Cdk5 inhibition interferes with intracellular trafficking, a process crucial for cellular homeostasis and growth factor receptor signaling. Cdk5 inhibition resulted in an accumulation of enlarged vesicles and respective cargos in the perinuclear region, considerably impairing the extent and quality of growth factor receptor signaling. Thereby, Cdk5 inhibition offers a comprehensive approach to globally disturb growth factor receptor signaling that is superior to specific inhibition of individual growth factor receptors. Conclusion: Cdk5 inhibition represents an effective approach to improve sorafenib response and to prevent sorafenib treatment escape in HCC. Notably, Cdk5 is an addressable target frequently overexpressed in HCC, and with Dinaciclib, a clinically tested Cdk5 inhibitor is readily available. Thus, our study provides evidence for clinically evaluating the combination of sorafenib and Dinaciclib to improve the therapeutic situation for patients with advanced-stage HCC.

Effects of Positive Language and Profession on Trustworthiness and Credibility in Online Health Advice: Experimental Study.

BACKGROUND: When searching for health information, many people use the internet as their first source of information. In online health forums, for example, users post their questions and exchange health advice. In recent years, information givers from various professions have begun to use positive language (indicated by the frequent use of positively valenced adjectives) to communicate their information and persuade their audiences. OBJECTIVE: The goal of the current study was to answer the following research questions: (1) How does positive language, in comparison to neutral language, influence the trustworthiness of a person arguing in an online health forum and the credibility of their health claims; (2) How does working for a university, compared to working for a lobbying organization, influence the trustworthiness of a person arguing in an online health forum and the credibility of their health claims; and (3) Do the two factors of language style and professional affiliation interact with each other to influence trustworthiness and credibility judgments? METHODS: In a 2 × 2 between-subject experiment, 242 participants read a post from an online health forum and subsequently rated the trustworthiness of the forum post author and the credibility of their information. Within the post, the professional affiliation (scientist vs lobbyist) and language style (neutral vs positive) of the forum post author was varied. RESULTS: When the forum post author used a positive language style, they were perceived as less trustworthy (high Machiavellianism [P<.001; η2p=.076], low Integrity [P=.001; η2p=.045], and low Benevolence [P=.02; η2p=.025]) and their information was perceived as less credible (low Message Credibility [P=.001; η2p=.045]). The professional affiliation of the forum post author did not influence their trustworthiness or the credibility of their information. CONCLUSIONS: When searching for health information, information seekers evaluate the language style of forum posts to decide whether forum post authors are trustworthy and their information is credible.

Quantitative and spatio-temporal features of protein aggregation in Escherichia coli and consequences on protein quality control and cellular ageing.

The aggregation of proteins as a result of intrinsic or environmental stress may be cytoprotective, but is also linked to pathophysiological states and cellular ageing. We analysed the principles of aggregate formation and the cellular strategies to cope with aggregates in Escherichia coli using fluorescence microscopy of thermolabile reporters, EM tomography and mathematical modelling. Misfolded proteins deposited at the cell poles lead to selective re-localization of the DnaK/DnaJ/ClpB disaggregating chaperones, but not of GroEL and Lon to these sites. Polar aggregation of cytosolic proteins is mainly driven by nucleoid occlusion and not by an active targeting mechanism. Accordingly, cytosolic aggregation can be efficiently re-targeted to alternative sites such as the inner membrane in the presence of site-specific aggregation seeds. Polar positioning of aggregates allows for asymmetric inheritance of damaged proteins, resulting in higher growth rates of damage-free daughter cells. In contrast, symmetric damage inheritance of randomly distributed aggregates at the inner membrane abrogates this rejuvenation process, indicating that asymmetric deposition of protein aggregates is important for increasing the fitness of bacterial cell populations.

Digital Health Literacy of the Population in Germany and Its Association With Physical Health, Mental Health, Life Satisfaction, and Health Behaviors: Nationally Representative Survey Study.

BACKGROUND: Digital health literacy, also known as eHealth literacy, describes the ability to seek, find, understand, and apply health information from the internet to address health problems. The World Health Organization calls for actions to improve digital health literacy. To develop target group-specific digital health literacy interventions, it is necessary to know the digital health literacy of the general population and relevant subgroups. OBJECTIVE: This study aims to representatively assess the digital health literacy of the population in Germany and relevant subgroups. The results are meant to facilitate the development of target group-specific digital health literacy interventions. Additionally, this study further explores the associations between digital health literacy and physical health, mental health, life satisfaction, and diverse health behaviors. METHODS: Study participants were drawn from a representative panel of the German-speaking population with internet access. To further increase the representativeness of the sample, survey weights were calculated using an iterative proportional fitting procedure. Participants answered a series of questionnaires regarding their digital health literacy, physical health, mental health, life satisfaction, and diverse health behaviors. Two-sided independent sample t tests were conducted to determine the significant differences between societal subgroups. Pearson correlation coefficients were calculated to explore the correlates of digital health literacy. RESULTS: Digital health literacy is unevenly distributed within German society. The results of this study suggest that people with a low level of formal education and people with a low social status would benefit from digital health literacy interventions that address their competencies in the domains of information seeking and information appraisal. Furthermore, the results suggest that older people would likely benefit from digital health literacy interventions that address their competencies in the domains of information seeking and also information appraisal. Regarding sex, this study suggests that men might benefit from digital health literacy interventions that specifically address their competencies in the domain of information seeking. Furthermore, digital health literacy is weakly positively correlated with physical health, mental health, life satisfaction, exercise routines, fruit consumption, and vegetable consumption. CONCLUSIONS: Overall, the results of this study demonstrate that digital health literacy is associated with diverse health outcomes and behaviors. Furthermore, the results provide a starting point for the development of target group-specific digital health literacy interventions.

T cells armed with C-X-C chemokine receptor type 6 enhance adoptive cell therapy for pancreatic tumours.

The efficacy of adoptive cell therapy for solid tumours is hampered by the poor accumulation of the transferred T cells in tumour tissue. Here, we show that forced expression of C-X-C chemokine receptor type 6 (whose ligand is highly expressed by human and murine pancreatic cancer cells and tumour-infiltrating immune cells) in antigen-specific T cells enhanced the recognition and lysis of pancreatic cancer cells and the efficacy of adoptive cell therapy for pancreatic cancer. In mice with subcutaneous pancreatic tumours treated with T cells with either a transgenic T-cell receptor or a murine chimeric antigen receptor targeting the tumour-associated antigen epithelial cell adhesion molecule, and in mice with orthotopic pancreatic tumours or patient-derived xenografts treated with T cells expressing a chimeric antigen receptor targeting mesothelin, the T cells exhibited enhanced intratumoral accumulation, exerted sustained anti-tumoral activity and prolonged animal survival only when co-expressing C-X-C chemokine receptor type 6. Arming tumour-specific T cells with tumour-specific chemokine receptors may represent a promising strategy for the realization of adoptive cell therapy for solid tumours.

Influence of Enthusiastic Language on the Credibility of Health Information and the Trustworthiness of Science Communicators: Insights From a Between-Subject Web-Based Experiment.

BACKGROUND: To decide whether online health information is reliable, information seekers apply 2 stretegies: first, information seekers can make credibility judgments by using their prior knowledge to evaluate the validity of the encountered health claim. Second, instead of evaluating the health claim itself, information seekers can make trustworthiness judgments by evaluating the character of the information source. In recent years, information givers from various professions have begun to use enthusiastic language to disseminate their information and persuade their audiences. OBJECTIVE: To systematically explore this phenomenon, the goal of this study was to answer the following research questions: (1) does an enthusiastic language style, in comparison with a neutral language style, increase the trustworthiness of a person arguing in an online health forum and the credibility of his or her information? (2) does working for a university, in comparison with working for a lobbying organization, increase the trustworthiness of a person arguing in an online health forum and the credibility of his or her information? (3) does working for a university in combination with using an enthusiastic language style result in especially high trustworthiness and credibility ratings? METHODS: In a 2x2 between-subject online experiment, 270 participants read a post from an online health forum and subsequently rated the trustworthiness of the forum post author and the credibility of his information. A total of 2 aspects of the forum post varied, namely the professional affiliation of the forum post author (whether the person introduced himself as a scientist or a lobbyist) and his language style (whether he used a neutral language style or an enthusiastic language style). RESULTS: When the forum post author used an enthusiastic language style, he was perceived as more manipulative (P<.001), less knowledgeable (P<.001), and his information was perceived as less credible (P<.001). Overall, scientists were perceived as less manipulative (P=.04) than lobbyists. Furthermore, language style and professional affiliation interacted: When the forum post author was a lobbyist, language style did not affect integrity (P=.96) and benevolence (P=.79) ratings. However, when the forum post author was a scientist, enthusiastic language led to lower integrity (P=.002) and benevolence (P<.001) ratings than neutral language. CONCLUSIONS: The current findings illustrate that health information seekers do not just react to online health information itself. In addition, they are also sensitive to the ways in which health information is presented ("Which langue style is used to communicate health information?") and who presents it ("Who does the health information source work for?").

Hot topics in science communication: Aggressive language decreases trustworthiness and credibility in scientific debates.

Current scientific debates, such as on climate change, often involve emotional, hostile, and aggressive rhetorical styles. Those who read or listen to these kinds of scientific arguments have to decide whom they can trust and which information is credible. This study investigates how the language style (neutral vs aggressive) and the professional affiliation (scientist vs lobbyist) of a person arguing in a scientific debate influence his trustworthiness and the credibility of his information. In a 2 X 2 between-subject online experiment, participants watched a scientific debate. The results show that if the person was introduced as a lobbyist, he was perceived as less trustworthy. However, the person's professional affiliation did not affect the credibility of his information. If the person used an aggressive language style, he was perceived as less trustworthy. Furthermore, his information was perceived as less credible, and participants had the impression that they learned less from the scientific debate.

Utility of the RIG-I Agonist Triphosphate RNA for Melanoma Therapy.

The pattern recognition receptor RIG-I plays an important role in the recognition of nonself RNA and antiviral immunity. RIG-I's natural ligand, triphosphate RNA (ppp-RNA), is proposed to be a valuable addition to the growing arsenal of cancer immunotherapy treatment options. In this study, we present comprehensive data validating the concept and utility of treatment with synthetic RIG-I agonist ppp-RNA for the therapy of human cancer, with melanoma as potential entry indication amenable to intratumoral treatment. Using mRNA expression data of human tumors, we demonstrate that RIG-I expression is closely correlated to cellular and cytokine immune activation in a wide variety of tumor types. Furthermore, we confirm susceptibility of cancer cells to ppp-RNA treatment in different cellular models of human melanoma, revealing unexpected heterogeneity between cell lines in their susceptibility to RNA agonist features, including sequence, secondary structures, and presence of triphosphate. Cellular responses to RNA treatment (induction of type I IFN, FasR, MHC-I, and cytotoxicity) were demonstrated to be RIG-I dependent using KO cells. Following ppp-RNA treatment of a mouse melanoma model, we observed significant local and systemic antitumor effects and survival benefits. These were associated with type I IFN response, tumor cell apoptosis, and innate and adaptive immune cell activation. For the first time, we demonstrate systemic presence of tumor antigen-specific CTLs following treatment with RIG-I agonists. Despite potential challenges in the generation and formulation of potent RIG-I agonists, ppp-RNA or analogues thereof have the potential to play an important role for cancer treatment in the next wave of immunotherapy.

Deformable image registration for adaptive radiotherapy with guaranteed local rigidity constraints.

BACKGROUND: Deformable image registration (DIR) is a key component in many radiotherapy applications. However, often resulting deformations are not satisfying, since varying deformation properties of different anatomical regions are not considered. To improve the plausibility of DIR in adaptive radiotherapy in the male pelvic area, this work integrates a local rigidity deformation model into a DIR algorithm. METHODS: A DIR framework is extended by constraints, enforcing locally rigid deformation behavior for arbitrary delineated structures. The approach restricts those structures to rigid deformations, while surrounding tissue is still allowed to deform elastically. The algorithm is tested on ten CT/CBCT male pelvis datasets with active rigidity constraints on bones and prostate and compared to the Varian SmartAdapt deformable registration (VSA) on delineations of bladder, prostate and bones. RESULTS: The approach with no rigid structures (REG0) obtains an average dice similarity coefficient (DSC) of 0.87 ± 0.06 and a Hausdorff-Distance (HD) of 8.74 ± 5.95 mm. The new approach with rigid bones (REG1) yields a DSC of 0.87 ± 0.07, HD 8.91 ± 5.89 mm. Rigid deformation of bones and prostate (REG2) obtains 0.87 ± 0.06, HD 8.73 ± 6.01 mm, while VSA yields a DSC of 0.86 ± 0.07, HD 10.22 ± 6.62 mm. No deformation grid foldings are observed for REG0 and REG1 in 7 of 10 cases; for REG2 in 8 of 10 cases, with no grid foldings in prostate, an average of 0.08 % in bladder (REG2: no foldings) and 0.01 % inside the body contour. VSA exhibits grid foldings in each case, with an average percentage of 1.81 % for prostate, 1.74 % for bladder and 0.12 % for the body contour. While REG1 and REG2 keep bones rigid, elastic bone deformations are observed with REG0 and VSA. An average runtime of 26.2 s was achieved with REG1; 31.1 s with REG2, compared to 10.5 s with REG0 and 10.7 s with VMS. CONCLUSIONS: With accuracy in the range of VSA, the new approach with constraints delivers physically more plausible deformations in the pelvic area with guaranteed rigidity of arbitrary structures. Although the algorithm uses an advanced deformation model, clinically feasible runtimes are achieved.

The immunoglobulin tail tyrosine motif upgrades memory-type BCRs by incorporating a Grb2-Btk signalling module.

The vigorous response of IgG-switched memory B cells to recurring pathogens involves enhanced signalling from their B-cell antigen receptors (BCRs). However, the molecular signal amplification mechanisms of memory-type BCRs remained unclear. Here, we identify the immunoglobulin tail tyrosine (ITT) motif in the cytoplasmic segments of membrane-bound IgGs (mIgGs) as the principle signal amplification device of memory-type BCRs in higher vertebrates and decipher its signalling microanatomy. We show that different families of protein tyrosine kinases act upstream and downstream of the ITT. Spleen tyrosine kinase (Syk) activity is required for ITT phosphorylation followed by recruitment of the adaptor protein Grb2 into the mIgG-BCR signalosome. Grb2 in turn recruits Bruton's tyrosine kinase (Btk) to amplify BCR-induced Ca(2+) mobilization. This molecular interplay of kinases and adaptors increases the antigen sensitivity of memory-type BCRs, which provides a cell-intrinsic trigger mechanism for the rapid reactivation of IgG-switched memory B cells on antigen recall.