Age-associated accumulation of B cells promotes macrophage inflammation and inhibits lipolysis in adipose tissue during sepsis.

Non-canonical lipolysis induced by inflammatory cytokines or Toll-like receptor ligands is required for the regulation of inflammation during endotoxemia and sepsis. Canonical lipolysis induced by catecholamines declines during aging due to factors including an expansion of lymphocytes, pro-inflammatory macrophage polarization, and an increase in chronic low-grade inflammation; however, the extent to which the non-canonical pathway of lipolysis is active and impacted by immune cells during aging remains unclear. Therefore, we aimed to define the extent to which immune cells from old mice influence non-canonical lipolysis during sepsis. We identified age-associated impairments of non-canonical lipolysis and an accumulation of dysfunctional B1 B cells in the visceral white adipose tissue (vWAT) of old mice. Lifelong deficiency of B cells results in restored non-canonical lipolysis and reductions in pro-inflammatory macrophage populations. Our study suggests that targeting the B cell-macrophage signaling axis may resolve metabolic dysfunction in aged vWAT and attenuate septic severity in older individuals.

CD115+ monocytes protect microbially experienced mice against E. coli-induced sepsis.

Uropathogenic E. coli (UPEC) is a primary organism responsible for urinary tract infections and a common cause of sepsis. Microbially experienced laboratory mice, generated by cohousing with pet store mice, exhibit increased morbidity and mortality to polymicrobial sepsis or lipopolysaccharide challenge. By contrast, cohoused mice display significant resistance, compared with specific pathogen-free mice, to a monomicrobial sepsis model using UPEC. CD115+ monocytes mediate protection in the cohoused mice, as depletion of these cells leads to increased mortality and UPEC pathogen burden. Further study of the cohoused mice reveals increased TNF-α production by monocytes, a skewing toward Ly6ChiCD115+ "classical" monocytes, and enhanced egress of Ly6ChiCD115+ monocytes from the bone marrow. Analysis of cohoused bone marrow also finds increased frequency and number of myeloid multipotent progenitor cells. These results show that a history of microbial exposure impacts innate immunity in mice, which can have important implications for the preclinical study of sepsis.

Reduced T Cell Priming in Microbially Experienced "Dirty" Mice Results from Limited IL-27 Production by XCR1+ Dendritic Cells.

Successful vaccination strategies offer the potential for lifelong immunity against infectious diseases and cancer. There has been increased attention regarding the limited translation of some preclinical findings generated using specific pathogen-free (SPF) laboratory mice to humans. One potential reason for the difference between preclinical and clinical findings lies in maturation status of the immune system at the time of challenge. In this study, we used a "dirty" mouse model, where SPF laboratory mice were cohoused (CoH) with pet store mice to permit microbe transfer and immune system maturation, to investigate the priming of a naive T cell response after vaccination with a peptide subunit mixed with polyinosinic-polycytidylic acid and agonistic anti-CD40 mAb. Although this vaccination platform induced robust antitumor immunity in SPF mice, it failed to do so in microbially experienced CoH mice. Subsequent investigation revealed that despite similar numbers of Ag-specific naive CD4 and CD8 T cell precursors, the expansion, differentiation, and recall responses of these CD4 and CD8 T cell populations in CoH mice were significantly reduced compared with SPF mice after vaccination. Evaluation of the dendritic cell compartment revealed reduced IL-27p28 expression by XCR1+ dendritic cells from CoH mice after vaccination, correlating with reduced T cell expansion. Importantly, administration of recombinant IL-27:EBI3 complex to CoH mice shortly after vaccination significantly boosted Ag-specific CD8 and CD4 T cell expansion, further implicating the defect to be T cell extrinsic. Collectively, our data show the potential limitation of exclusive use of SPF mice when testing vaccine efficacy.

A dominant function of LynB kinase in preventing autoimmunity.

Here, we report that the LynB splice variant of the Src-family kinase Lyn exerts a dominant immunosuppressive function in vivo, whereas the LynA isoform is uniquely required to restrain autoimmunity in female mice. We used CRISPR-Cas9 gene editing to constrain lyn splicing and expression, generating single-isoform LynA knockout (LynAKO) or LynBKO mice. Autoimmune disease in total LynKO mice is characterized by production of antinuclear antibodies, glomerulonephritis, impaired B cell development, and overabundance of activated B cells and proinflammatory myeloid cells. Expression of LynA or LynB alone uncoupled the developmental phenotype from the autoimmune disease: B cell transitional populations were restored, but myeloid cells and differentiated B cells were dysregulated. These changes were isoform-specific, sexually dimorphic, and distinct from the complete LynKO. Despite the apparent differences in disease etiology and penetrance, loss of either LynA or LynB had the potential to induce severe autoimmune disease with parallels to human systemic lupus erythematosus (SLE).

Polymicrobial Sepsis Impairs Antigen-Specific Memory CD4 T Cell-Mediated Immunity.

Patients who survive sepsis display prolonged immune dysfunction and heightened risk of secondary infection. CD4 T cells support a variety of cells required for protective immunity, and perturbations to the CD4 T cell compartment can decrease overall immune system fitness. Using the cecal ligation and puncture (CLP) mouse model of sepsis, we investigated the impact of sepsis on endogenous Ag-specific memory CD4 T cells generated in C57BL/6 (B6) mice infected with attenuated Listeria monocytogenes (Lm) expressing the I-Ab-restricted 2W1S epitope (Lm-2W). The number of 2W1S-specific memory CD4 T cells was significantly reduced on day 2 after sepsis induction, but recovered by day 14. In contrast to the transient numerical change, the 2W1S-specific memory CD4 T cells displayed prolonged functional impairment after sepsis, evidenced by a reduced recall response (proliferation and effector cytokine production) after restimulation with cognate Ag. To define the extent to which the observed functional impairments in the memory CD4 T cells impacts protection to secondary infection, B6 mice were infected with attenuated Salmonella enterica-2W (Se-2W) 30 days before sham or CLP surgery, and then challenged with virulent Se-2W after surgery. Pathogen burden was significantly higher in the CLP-treated mice compared to shams. Similar reductions in functional capacity and protection were noted for the endogenous OVA323-specific memory CD4 T cell population in sepsis survivors upon Lm-OVA challenge. Our data collectively show CLP-induced sepsis alters the number and function of Ag-specific memory CD4 T cells, which contributes (in part) to the characteristic long-lasting immunoparalysis seen after sepsis.

Microbial Exposure Enhances Immunity to Pathogens Recognized by TLR2 but Increases Susceptibility to Cytokine Storm through TLR4 Sensitization.

Microbial exposures can define an individual's basal immune state. Cohousing specific pathogen-free (SPF) mice with pet store mice, which harbor numerous infectious microbes, results in global changes to the immune system, including increased circulating phagocytes and elevated inflammatory cytokines. How these differences in the basal immune state influence the acute response to systemic infection is unclear. Cohoused mice exhibit enhanced protection from virulent Listeria monocytogenes (LM) infection, but increased morbidity and mortality to polymicrobial sepsis. Cohoused mice have more TLR2+ and TLR4+ phagocytes, enhancing recognition of microbes through pattern-recognition receptors. However, the response to a TLR2 ligand is muted in cohoused mice, whereas the response to a TLR4 ligand is greatly amplified, suggesting a basis for the distinct response to Listeria monocytogenes and sepsis. Our data illustrate how microbial exposure can enhance the immune response to unrelated challenges but also increase the risk of immunopathology from a severe cytokine storm.

Use of Machine Learning to Identify Follow-Up Recommendations in Radiology Reports.

PURPOSE: The aims of this study were to assess follow-up recommendations in radiology reports, develop and assess traditional machine learning (TML) and deep learning (DL) models in identifying follow-up, and benchmark them against a natural language processing (NLP) system. METHODS: This HIPAA-compliant, institutional review board-approved study was performed at an academic medical center generating >500,000 radiology reports annually. One thousand randomly selected ultrasound, radiography, CT, and MRI reports generated in 2016 were manually reviewed and annotated for follow-up recommendations. TML (support vector machines, random forest, logistic regression) and DL (recurrent neural nets) algorithms were constructed and trained on 850 reports (training data), with subsequent optimization of model architectures and parameters. Precision, recall, and F1 score were calculated on the remaining 150 reports (test data). A previously developed and validated NLP system (iSCOUT) was also applied to the test data, with equivalent metrics calculated. RESULTS: Follow-up recommendations were present in 12.7% of reports. The TML algorithms achieved F1 scores of 0.75 (random forest), 0.83 (logistic regression), and 0.85 (support vector machine) on the test data. DL recurrent neural nets had an F1 score of 0.71; iSCOUT also had an F1 score of 0.71. Performance of both TML and DL methods by F1 scores appeared to plateau after 500 to 700 samples while training. CONCLUSIONS: TML and DL are feasible methods to identify follow-up recommendations. These methods have great potential for near real-time monitoring of follow-up recommendations in radiology reports.