We have previously reported that differences in early production of interleukin 12 (IL-12) by dendritic cells (DC) underlies the difference between the susceptibilities toListeria monocytogenesof C57BL/6 and BALB/c mice. To elucidate mechanisms for the different abilities of DC to produce cytokine in C57BL/6 and BALB/c mice, we examined Toll-like receptor (TLR) expression by DC and their responses in vitro to known microbial ligands for TLRs. We found that DC isolated from the spleens of naive C57BL/6 mice preferentially expressed TLR9 mRNA, whereas DC from naive BALB/c mice strongly expressed TLR2, -4, -5, and -6 mRNAs. C57BL/6 DC produced a higher level of IL-12p40 in response to the ligands for TLR4 (lipopolysaccharide), TLR2 (lipoprotein), and TLR9 (CpG), whereas BALB/c DC responded to these ligands by producing a larger amount of monocyte chemoattractant protein 1. C57BL/6 DC expressed higher levels of CD40 and Stat4 than BALB/c DC did, suggesting that naive C57BL/6 mice contained more-mature subsets of DC than naive BALB/c mice. Differences in reactivities of DC to microbial molecules through TLRs may be associated with susceptibility and resistance toListeriainfection in BALB/c and C57BL/6 mice.

Tertiary lymphoid tissues (TLTs) facilitate local T and B cell interactions in chronically inflamed organs. However, the cells and molecular pathways that govern TLT formation are poorly defined. Here, we identified TNF superfamily CD153/CD30 signaling between 2 unique age-dependent lymphocyte subpopulations, CD153⁺PD-1⁺CD4⁺ senescence-associated T (SAT) cells and CD30⁺T-bet⁺ age-associated B cells (ABCs), as a driver for TLT expansion. SAT cells, which produced ABC-inducing factors IL-21 and IFN-γ, and ABCs progressively accumulated within TLTs in aged kidneys after injury. Notably, in kidney injury models, CD153 or CD30 deficiency impaired functional SAT cell induction, which resulted in reduced ABC numbers and attenuated TLT formation with improved inflammation, fibrosis, and renal function. Attenuated TLT formation after transplantation of CD153-deficient bone marrow further supported the importance of CD153 in immune cells. Clonal analysis revealed that SAT cells and ABCs in the kidneys arose from both local differentiation and recruitment from the spleen. In the synovium of aged rheumatoid arthritis patients, T peripheral helper/T follicular helper cells and ABCs also expressed CD153 and CD30, respectively. Together, our data reveal a previously unappreciated function of CD153/CD30 signaling in TLT formation and propose targeting the CD153/CD30 signaling pathway as a therapeutic target for slowing kidney disease progression.

Interaction between commensal bacteria and intestinal epithelial cells (i-ECs) via TLRs is important for intestinal homeostasis. In this study, we found that the numbers of CD8αα TCRαβ and TCRγδ intestinal intraepithelial lymphocytes (i-IELs) were significantly decreased in MyD88-deficient (−/−) mice. The expression of IL-15 by i-ECs was severely reduced in MyD88^−/− mice. Introduction of IL-15 transgene into MyD88^−/− mice (MyD88^−/− IL-15 transgenic mice) partly restored the numbers of CD8αα TCRαβ and TCRγδ i-IELs. The i-IEL in irradiated wild-type (WT) mice transferred with MyD88^−/− bone marrow (BM) cells had the same proportions of i-IEL as WT mice, whereas those in irradiated MyD88^−/− mice transferred with WT BM cells showed significantly reduced proportions of CD8αα TCRαβ and TCRγδ i-IELs, as was similar to the proportions found in MyD88^−/− mice. However, irradiated MyD88^−/− IL-15 transgenic mice transferred with WT BM cells had increased numbers of CD8αα TCRαβ and TCRγδ subsets in the i-IEL. These results suggest that parenchymal cells such as i-ECs contribute to the maintenance of CD8αα TCRαβ and γδ i-IELs at least partly via MyD88-dependent IL-15 production.

IL-17A–producing γδ T cells in mice consist primarily of Vγ6+ tissue-resident cells and Vγ4+ circulating cells. How these γδ T cell subsets are regulated during homeostasis and cancer remains poorly understood. Using single-cell RNA sequencing and flow cytommetry, we show that lung Vγ4+ and Vγ6+ cells from tumor-free and tumor-bearing mice express contrasting cell surface molecules as well as distinct co-inhibitory molecules, which function to suppress their expansion. Vγ6+ cells express constitutively high levels of PD-1, whereas Vγ4+ cells upregulate TIM-3 in response to tumor-derived IL-1β and IL-23. Inhibition of either PD-1 or TIM-3 in mammary tumor–bearing mice increased Vγ6+ and Vγ4+ cell numbers, respectively. We found that genetic deletion of γδ T cells elicits responsiveness to anti–PD-1 and anti–TIM-3 immunotherapy in a mammary tumor model that is refractory to T cell checkpoint inhibitors, indicating that IL-17A–producing γδ T cells instigate resistance to immunotherapy. Together, these data demonstrate how lung IL-17A–producing γδ T cell subsets are differentially controlled by PD-1 and TIM-3 in steady-state and cancer.

Highly pathogenic influenza A viruses cause acute severe pneumonia to which the occurrence of “cytokine storm” has been proposed to contribute. Here we show that interleukin-15 (IL-15) knockout (KO) mice exhibited reduced mortality after infection with influenza virus A/FM/1/47 (H1N1, a mouse-adapted strain) albeit the viral titers of these mice showed no difference from those of control mice. There were significantly fewer antigen-specific CD44 ⁺ CD8 ⁺ T cells in the lungs of infected IL-15 KO mice, and adoptive transfer of the CD8 ⁺ T cells caused reduced survival of IL-15 KO mice following influenza virus infection. Mice deficient in β ₂ -microglobulin by gene targeting and those depleted of CD8 ⁺ T cells by in vivo administration of anti-CD8 monoclonal antibody displayed a reduced mortality rate after infection. These results indicate that IL-15-dependent CD8 ⁺ T cells are at least partly responsible for the pathogenesis of acute pneumonia caused by influenza A virus.