IL-12 is required for mTOR regulation of memory CTLs during viral infection

Safety of selective IL-23p19 inhibitors for the treatment of psoriasis

Psoriasis is a chronic disease that requires long‐term treatment. Consequently, understanding the safety and tolerability of any potential treatment over time is critical to effective prescribing. The biologic agents currently available for the treatment of psoriasis target a number of different inflammatory cytokines involved in psoriasis disease pathogenesis. The monoclonal antibodies tildrakizumab, guselkumab and risankizumab target the p19 subunit that is specific to interleukin (IL)‐23. This article reviews published data on the safety of these IL‐23p19 inhibitors in patients with psoriasis compared with other currently available biologic therapies. Data from randomized, placebo‐ and active‐controlled phase 3 clinical trials show tildrakizumab, guselkumab and risankizumab to have a favourable risk–benefit profile in patients with moderate to severe psoriasis. No significant safety concerns have been observed for any of these IL‐23p19 inhibitors in the data published to date. The most commonly reported adverse events (AEs) associated with these agents in phase 3 studies were upper respiratory tract infections. No increase was seen in rates of serious infections, malignancies or major adverse cardiovascular events, with no signals suggestive of an elevated risk of opportunistic infections, active tuberculosis or reactivation of latent tuberculosis infection, mucocutaneous Candida infections, triggering or worsening of inflammatory bowel disease, demyelinating disorders or suicidal ideation. Selectively targeting IL‐23p19 may help avoid AEs that have been associated with biologic agents with other mechanisms of action. Data from long‐term extension studies and patient registries will further establish the safety profile of IL‐23p19 inhibitors for the treatment of moderate to severe psoriasis in routine practice.

Effector functions of memory CTLs can be affected by signals received during reactivation

Memory cytotoxic T lymphocytes (CTLs) are able to provide protections to the host against repeated insults from intracellular pathogens. However, it has not been completely understood how the effector functions of memory CTLs are induced upon antigen challenge, which is directly related to the efficacy of their protection. Third signal cytokines, such as IL-12 and type I interferon, have been suggested to be involved in the protective function of memory CTLs, but direct evidence is warranted. In this report, we found that memory CTLs need to be reactivated to exert effector functions. Infusion of a large population of quiescent memory CTLs did not lead to cancer control in tumor-bearing mice, whereas infusion of a reactivated memory CTL population did. This reactivation of memory CTLs requires cytokines such as IL-12 in addition to antigen but was less dependent upon costimulation and IL-2 compared to naive CTLs. Memory CTLs responded more quickly and with greater strength than their naive counterparts upon stimulation, which is associated with higher upregulation of important transcription factors such as T-bet and phosphorylated STAT4. In addition, memory CTLs underwent less expansion than naive CTLs upon pathogen challenge. In conclusion, effector functions of established memory CTLs may be affected by certain cytokines such as IL-12 and type I IFN. Thus, a pathogen's ability to induce cytokines could contribute to the efficacy of protection of an established memory CTL population.

Changes and significance of inflammatory cytokines in a rat model of cervical spondylosis

The aim of the present study was to dynamically observe and discuss the significance of inflammatory cytokines in cervical degenerative disease induced by unbalanced dynamic and static forces in rats. A total of 60 Sprague Dawley rats were randomized into test (n=45) and control (n=15) groups, which were randomly subdivided into three groups corresponding to assessment at one, three and six months post-operation. The test group included 10, 15 and 20 rats at the corresponding post-operative stage and the control group had five rats at each time-point. By excising cervicodorsal muscles and ligaments, an unbalanced dynamic and static rat model was established in the test group. At one, three and six-months post-operation, venous serum of test and control group rats was collected and inflammatory cytokines in the serum of all rats were quantitatively determined by ELISA. The results revealed that compared with the control group, the interleukin (IL)-1β, IL-10 and tumor necrosis factor-α levels in the test group were significantly increased at one and three months (P<0.05, <0.01 or <0.001), and that IL-12 was significantly increased at three months (P<0.05). However, transforming growth factor-β1 increased at one month but was significantly decreased at three months (P<0.01). IL-6 did not change significantly throughout the observation period (P>0.05). In conclusion, cervical vertebral stability may be accompanied with changes of inflammatory cytokines.

IL-12 stimulates CTLs to secrete exosomes capable of activating bystander CD8+ T cells

An effective cytotoxic T lymphocyte (CTL) response against intracellular pathogens is generally accomplished by immense CTL expansion and activation, which can destroy infected cells. Vigorous immune responses can lead to activation of bystander CD8⁺ T cells, but the contribution from antigen-specific CTLs is not well understood. We found that CTLs secrete extracellular vesicles following antigen stimulation. These CTL-derived vesicles contain CTL proteins and exhibit markers and size profiles consistent with exosomes. Interestingly, further stimulation of CTLs with IL-12 impacts exosome size and leads to selective enrichment of certain exosomal proteins. More important, exosomes from IL-12-stimulated CTLs directly activated bystander naïve CD8⁺ T cells to produce interferon-γ (IFNγ) and granzyme B (GZB) in the absence of antigens, whereas control exosomes derived from antigen-stimulated CTLs did not. In addition, IL-12 induced exosomes are able to strengthen the effects of weak antigen stimulation on CTLs. Proteomic analysis demonstrates that IL-12 stimulation alters catalytic and binding activities of proteins in CTL exosomes. Our findings indicate that the biological function and morphology of exosomes secreted by CTLs can be influenced by the type of stimulation CTLs receive. Thus, a fully functional, ongoing, antigen-specific CTL response may influence bystander CD8⁺ T cells through secretion of exosomes.

mTOR Regulation of Lymphoid Cells in Immunity to Pathogens

Immunity to pathogens exists as a fine balance between promoting activation and expansion of effector cells, while simultaneously limiting normal and aberrant responses. These seemingly opposing functions are kept in check by immune regulators. The mechanistic target of rapamycin (mTOR) is a serine/threonine kinase that senses nutrient availability and, in turn, regulates cell metabolism, growth, and survival accordingly. mTOR plays a pivotal role in facilitating immune defense against invading pathogens by regulating the differentiation, activation, and effector functions of lymphoid cells. Here, we focus on the emerging and sometimes contradictory roles of mTOR in orchestrating lymphoid cell-mediated host immune responses to pathogens. A thorough understanding of how mTOR impacts lymphoid cells in pathogen defense will provide the necessary base for developing therapeutic interventions for infectious diseases.

Making many from few: IL-12p40 as a model for the combinatorial assembly of heterodimeric cytokines

How dendritic cells (DCs) gather information from the local milieu at a site of infection or injury and communicate this to influence adaptive immunity is not well understood. We and others have reported that soon after microbial encounter, DCs secrete the p40 subunit of IL-12, by itself, in a monomeric form. Based on recent data that this p40 monomer subsequently associates with p35 released from other cells to generate functional IL-12, we proposed that p40 can function as a DC-derived probe which samples the composition of the local milieu by looking for other binding partners. In this opinion, we discuss how such a sampling function might generate an elaborate combinatorial "code" of heterodimeric cytokines, capable of conveying location-specific information to cells downstream of DC activation, including NK and T cells.

Regulation of T cells by mTOR: the known knowns and the known unknowns

Mammalian/mechanistic target of rapamycin (mTOR) is emerging as an important integrator of environmental cues critical for the regulation of T cell activation, differentiation, and function. Recent studies leveraging pharmacologic inhibition or T cell specific genetic deletion of signaling components in the mTOR pathway have provided important insights into the mechanisms involved, and have been informative in defining targets downstream of mTOR that promote immune regulation. However, these studies have also presented confusing and, at times, contradictory findings, highlighting the complexities involved in examining the mTOR pathway in distinct contexts. Here, we review current understanding of the roles of mTOR in T cell biology, highlighting emerging concepts and areas of investigation where the precise role of mTOR has yet to be fully discerned.