TLR signals license CD8 T cells to destroy oligodendrocytes expressing an antigen shared with a Listeria pathogen

CD8+ T cells recognizing a neuron-restricted antigen injure axons in a model of multiple sclerosis

CD8+ T cells outnumber CD4+ cells in multiple sclerosis (MS) lesions associated with disease progression, but the pathogenic role and antigenic targets of these clonally expanded effectors are unknown. Based on evidence that demyelination is necessary but not sufficient for disease progression in MS, we previously hypothesized that CNS-infiltrating CD8+ T cells specific for neuronal antigens directly drive the axonal and neuronal injury that leads to cumulative neurologic disability in patients with MS. We now show that demyelination induced expression of MHC class I on neurons and axons and resulted in presentation of a neuron-specific neoantigen (synapsin promoter-driven chicken ovalbumin) to antigen-specific CD8+ T cells (anti-ovalbumin OT-I TCR-transgenic T cells). These neuroantigen-specific effectors surveilled the CNS in the absence of demyelination but were not retained. However, upon induction of demyelination via cuprizone intoxication, neuroantigen-specific CD8+ T cells proliferated, accumulated in the CNS, and damaged neoantigen-expressing neurons and axons. We further report elevated neuronal expression of MHC class I and β2-microglobulin transcripts and protein in gray matter and white matter tracts in tissue from patients with MS. These findings support a pathogenic role for autoreactive anti-axonal and anti-neuronal CD8+ T cells in MS progression.

Myeloid MyD88 restricts CD8+ T cell response to radiation therapy in pancreatic cancer

Radiation therapy induces immunogenic cell death in cancer cells, whereby released endogenous adjuvants are sensed by immune cells to direct adaptive immune responses. TLRs expressed on several immune subtypes recognize innate adjuvants to direct downstream inflammatory responses in part via the adapter protein MyD88. We generated Myd88 conditional knockout mice to interrogate its contribution to the immune response to radiation therapy in distinct immune populations in pancreatic cancer. Surprisingly, Myd88 deletion in Itgax (CD11c)-expressing dendritic cells had little discernable effects on response to RT in pancreatic cancer and elicited normal T cell responses using a prime/boost vaccination strategy. Myd88 deletion in Lck-expressing T cells resulted in similar or worsened responses to radiation therapy compared to wild-type mice and lacked antigen-specific CD8+ T cell responses from vaccination, similar to observations in Myd88-/- mice. Lyz2-specific loss of Myd88 in myeloid populations rendered tumors more susceptible to radiation therapy and elicited normal CD8+ T cell responses to vaccination. scRNAseq in Lyz2-Cre/Myd88fl/fl mice revealed gene signatures in macrophages and monocytes indicative of enhanced type I and II interferon responses, and improved responses to RT were dependent on CD8+ T cells and IFNAR1. Together, these data implicate MyD88 signaling in myeloid cells as a critical source of immunosuppression that hinders adaptive immune tumor control following radiation therapy.

Sodium butyrate alleviates LPS-induced kidney injury via inhibiting TLR2/4 to regulate rBD2 expression

Defensins represent an integral part of the innate immune system to ward off potential pathogens. The study used a rat model to investigate mechanisms by which sodium butyrate (NaB) regulates β-defensin to inhibit lipopolysaccharide (LPS)-induced nephrotoxicity. We found that NaB alleviated LPS-induced renal structural damage, as judged by reduced renal lesions and improved glomerular vascular structure. In addition, elevated levels of indicators of kidney damage creatinine and blood urine nitrogen, inflammatory mediators TNF-α, and IL-6 dropped after NaB administration. Rat β-defensin 2 (rBD2), as estimated by mRNA level, was significantly higher in LPS-treated kidneys, whereas the changes of rBD2 reduced in NaB-treated kidneys. In addition, NaB alleviated LPS-induced increase in TLRs mRNA expression. Mechanistically, the present study indicates that NaB has nephroprotective activity resulting from modulation of TLR2/4 to regulate rBD2 expression hence curbing inflammation. PRACTICAL APPLICATIONS: In practice, adding NaB to diet can improve animal performance. Our results suggest that dietary supplementation of NaB increases animal feed intake and improves the body's defense ability to relieve inflammation caused by bacteria. Especially in the age of resistance prohibition, sodium butyrate can partially replace antibiotics to induce the expression of body defensin. It may become a health care product to enhance the body's immunity.

Activation of Toll-like receptor 2 enhances peripheral and tumor-infiltrating CD8+ T cell cytotoxicity in patients with gastric cancer

BACKGROUND

Toll-like receptors (TLRs) play central roles in the initiation of innate immune response, and also control adaptive immunity activation. Thus, the aim of the study was to investigate the regulation of TLR activation to CD8⁺ T cells has not been fully elucidated in gastric cancer (GC).

MATERIALS AND METHODS

Thirty-two GC patients and twenty-three healthy controls were enrolled. Expression profile of TLRs in peripheral and tumor-infiltrating CD8⁺ T cells was investigated. Purified CD8⁺ T cells were stimulated with Pam3Csk4, an agonist of TLR2, and cytotoxic and co-inhibitory molecules in CD8⁺ T cells was measured. Direct and indirect contact coculture system between CD8⁺ T cells and AGS cells was set up. Modulation of TLR2 activation to CD8⁺ T cells was assessed by measuring lactate dehydrogenase release and cytokine secretion.

RESULTS

TLR2 mRNA and TLR2⁺ cell percentage was down-regulated in GC derived peripheral and tumor-infiltrating CD8⁺ T cells. CD8⁺ T cells from GC patients showed exhausted phenotype, which presented as decreased perforin/granzyme B, increased programmed death-1, and reduced cytotoxicity to AGS cells. TLR2 activation by Pam3Csk4 enhanced perforin and granzyme B expression in CD8⁺ T cells, however, did not affect either proinflammatory cytokine production or co-inhibitory molecules expression. Pam3Csk4 stimulation enhanced cytolytic activation of peripheral and tumor-infiltrating CD8⁺ T cells from GC, but not those from healthy individuals.

CONCLUSION

The present data revealed an important immunomodulatory activity of TLR2 to CD8⁺ T cells in GC patients.

Toll-Like Receptor 2 Attenuates Traumatic Brain Injury-Induced Neural Stem Cell Proliferation in Dentate Gyrus of Rats

It was not clear how and whether neural stem cells (NSCs) responded to toll-like receptor 2 (TLR2) in the inflammatory environment after traumatic brain injury (TBI). The current study investigated the correlation of TLR2 and NSC proliferation in the dentate gyrus (DG) using the TBI model of rats. Immunofluorescence (IF) was used to observe the expression of BrdU, nestin, and TLR2 in the DG in morphology. Proliferating cells in the DG were labelled by thymidine analog 5-bromo-2-deoxyuridine (BrdU). Three-labelled BrdU, nestin, and DAPI was used for the identification of newly generated NSCs. Western blotting and real-time polymerase chain reaction (PCR) were used to observe the expression of TLR2 from the level of protein and mRNA. We observed that BrdU⁺/nestin⁺/DAPI⁺ cells accounted for 84.30% ± 6.54% among BrdU⁺ cells; BrdU⁺ and nestin⁺ cells in the DG were also TLR2⁺ cells. BrdU⁺ cells and the expression of TLR2 (both protein and mRNA levels) both elevated immediately at 6 hours (h), 24 h, 3 days (d), and 7 d posttrauma and peaked in 3 d. Results indicated that TLR2 was expressed on proliferating cells in the DG (NSCs possibly) and there was a potential correlation between increased TLR2 and proliferated NSCs after TBI. Taken together, these findings suggested that TLR2 was involved in endogenous neurogenesis in the DG after TBI.