Ultrasound Guided Intra-thymic Injection to Track Recent Thymic Emigrants and Investigate T Cell Development

To track recent thymic emigrants (RTEs) or study T cell development in the thymus, intra-thymic injection of a cellular tag or precursor cells for various T cell lineages is often desired. However, the traditional surgical approach to expose the thymus for intra-thymic injection is time-consuming and can cause a high level of pain and stress to animals, which might disrupt immune homeostasis, potentially confounding the results. Here, we introduce an ultrasound guided intra-thymic injection procedure, which is non-surgical and minimally invasive to animals. This technique is relatively easy to learn and offers an efficient and accurate tool to track RTEs or perform intra-thymic transfer of various cell types to investigate their differentiation.

From the Deep Sea to Everywhere: Environmental Antigens for iNKT Cells

Invariant natural killer T (iNKT) cells are a unique subset of innate T cells that share features with innate NK cells and adaptive memory T cells. The first iNKT cell antigen described was found 1993 in a marine sponge and it took over 10 years for other, bacterial antigens to be described. Given the paucity of known bacterial iNKT cell antigens, it appeared as if iNKT cells play a very specialist role in the protection against few, rare and unusual pathogenic bacteria. However, in the last few years several publications painted a very different picture, suggesting that antigens for iNKT cells are found almost ubiquitous in the environment. These environmental iNKT cell antigens can shape the distribution, phenotype and function of iNKT cells. Here, these recent findings will be reviewed and their implications for the field will be outlined.

Abnormalities in iNKT cells are associated with impaired ability of monocytes to produce IL-10 and suppress T-cell proliferation in sarcoidosis

Sarcoidosis is a multisystem granulomatous disorder characterized by marked T‐cell expansion of T helper 1 (Th1) cells. The cause of T‐cell overactivity is unknown. We hypothesized that interleukin‐10 (IL‐10) production by a yet undefined cell type might be defective, resulting in loss of regulation of T‐cell activity. Focusing on IL‐10‐producing monocytes, we first showed that monocytes isolated from the peripheral blood of corticosteroid‐naïve sarcoidosis patients (n = 51) produced less IL‐10 compared to controls, and were less able to suppress T‐cell proliferation. In addition, monocytic IL‐10 production correlated negatively with disease activity score. As invariant natural killer T (iNKT) cells are known to both interact with monocytes and be reduced in sarcoidosis patients, we then asked whether iNKT‐specific defects might be responsible for this reduced IL‐10 production. We found that greater numbers of circulating iNKT cells was associated with higher IL‐10 production. Moreover, iNKT cells enhanced monocytic IL‐10 production in vitro. Defective IL‐10 production and T‐cell suppression by sarcoidosis monocytes could be restored following their coculture with iNKT cells, in a CD1d‐ and cell contact‐dependent process. We suggest that reduced iNKT‐cell numbers in sarcoidosis may lead to impaired monocytic IL‐10 production and unchecked T‐cell expansion in sarcoidosis. These findings provide fresh insight into the mechanism of sarcoidosis disease, and interaction between iNKT cells and monocytes.

Invariant natural killer T (iNKT) cell exhaustion in sarcoidosis

Invariant natural killer T (iNKT) cells are integral components of immune responses during many chronic diseases, yet their surface phenotypes, subset distribution, and polyfunctional capacity in this environment are largely unknown. Therefore, using flow cytometry, we determined iNKT cell phenotypic and functional characteristics in subjects with chronic inflammatory disease sarcoidosis and matched controls. We found that sarcoidosis subjects displayed lower iNKT-cell frequencies, which correlated with lung fibrosis, C-reactive protein levels, and other measures of clinical disease. The CD4(-) CD8(-) (double negative, DN) iNKT-cell population was selectively lower in diseased individuals and the remaining DN iNKT cells exhibited higher frequencies of the activation markers CD69 and CD56. Functionally, both total IFN-γ(+) and the dual-functional IFN-γ(+) TNF-α(+) iNKT cells were decreased in sarcoidosis subjects and these functional defects correlated with total iNKT-cell circulating frequencies. As the loss of polyfunctionality can reflect functional exhaustion, we measured the surface antigens programmed death-1 receptor and CD57 and found that levels inversely correlated with dual-functional iNKT-cell percentages. These findings reveal that, similar to traditional T cells, iNKT cells may also undergo functional exhaustion, and that circulating iNKT-cell frequencies reflect these defects. Programmed death-1 receptor antagonists may therefore be attractive therapeutic candidates for sarcoidosis and other iNKT-cell-mediated chronic diseases.