Biology subjects

Kruger, P.

Publications and source records attributed to Kruger, P..

4 recordsLinked to original sources

bioRxiv2021

Differential impact of TNFRSF co-stimulation on CD8+ T cell cytokine production by feedback control of surface receptor expression

T cell responses towards infections and cancers are regulated by a host of co-signalling receptors that are largely grouped into the binary categories of co-stimulation and co-inhibition. The TNF receptor superfamily (TNFRSF) members 4-1BB, CD27, GITR, and OX40 are well-established co-stimulation receptors with largely shared molecular pathways raising the question of whether they also have a similar impact on quantitative T cell responses, such as the efficacy, sensitivity, and duration of T cell responses. Here, we systematically stimulated primary human CD8+ T cell blasts with dose ranges of antigen and ligands for TNFRSF members to screen for their quantitative effects on cytokine production. Although both 4-1BB and CD27 increased efficacy, only 4-1BB was able to prolong the duration of cytokine production, and both had only a modest impact on antigen sensitivity. An operational model could explain these divergent quantitative phenotypes using a shared signalling mechanism based on the surface expression of 4-1BB, but not CD27, being regulated through a signalling feedback. The model predicted that CD27 co-stimulation would increase 4-1BB expression and subsequent 4-1BB co-stimulation, which we confirmed experimentally. Although GITR and OX40 produced only minor changes in cytokine production on their own, we found that like 4-1BB, CD27 could enhance GITR expression and subsequent GITR co-stimulation. Thus, feedback control of induced TNFRSF surface expression explains both synergy and differential impact on cytokine production. The work highlights that different co-stimulation receptors can have different quantitative phenotypes on the same output allowing for highly regulated control of T cell responses.

immunology↗

bioRxiv2021

Improved spatio-temporal measurements of visually evoked fields using optically-pumped magnetometers

Recent developments in performance and practicality of optically pumped magnetometers have enabled new capabilities in non-invasive brain function mapping through magnetoencephalography. In particular the lack of need of cryogenic operating conditions allows for more flexible placement of the sensor heads closer to the brain surface, leading to improved spatial measurement resolution and increased source localisation capabilities. Through the recording of visually evoked brain fields (VEF), we demonstrate that the closer sensor proximity can be further exploited to improve the temporal resolution. We use optically pumped magnetometers (OPMs), and for reference superconducting quantum interference devices (SQUIDs), to measure brain responses to standard flash and pattern reversal stimuli. We find highly reproducible signals with consistency across multiple healthy participants, stimulus paradigms and sensor modalities. The temporal resolution advantage of OPMs is manifest in a fourfold improvement of the ratio of magnetic signal peak height to temporal width, compared to SQUIDs. The resulting capability of improved spatio-temporal signal tracing is illustrated by simultaneous vector recordings of VEFs in the primary (V1) and associative (V2) visual cortex, where a time lag on the order of 10-20 ms is consistently found. This paves the way for further studies of spatio-temporal neurophysiological signal tracking in visual stimulus processing and other brain responses with potentially far-reaching consequences for time-critical mapping of functionality in the healthy and pathological brains.

neuroscience↗

bioRxiv2020

Human CD8+ T cells exhibit a shared antigen threshold for different effector responses

T cells recognising cognate pMHC antigens become activated to elicit a myriad of cellular responses, such as target cell killing and the secretion of different cytokines, that collectively contribute to adaptive immunity. These effector responses have been hypothesised to exhibit different antigen dose and affinity thresholds, suggesting that pathogen-specific information may be encoded within the nature of the antigen. Here, using systematic experiments in a reductionist system, where primary human CD8+ T cell blasts are stimulated by recombinant pMHC antigen alone, we show that different inflammatory cytokines have comparable antigen dose thresholds across a 25,000-fold variation in affinity. Although co-stimulation by CD28, CD2, and CD27 increased cytokine production in this system, the antigen threshold remained comparable across different cytokines. When using primary human memory CD8+ T cells responding to autologous antigen presenting cells equivalent thresholds were also observed for cytokine production and killing. These findings imply a simple phenotypic model of TCR signalling where multiple T cell responses share a common rate-limiting threshold and a conceptually simple model of antigen recognition, where the chance factor of antigen dose and affinity do not provide any additional response-specific information.

immunology↗

bioRxiv2019

Perfect adaptation of CD8+ T cell responses to constant antigen input over a wide range of affinity is overcome by costimulation

Maintaining and limiting T cell responses to constant antigen stimulation is critical to control pathogens and maintain self-tolerance, respectively. Antigen recognition by T cell receptors (TCRs) induces signalling that activates T cells to produce cytokines and also leads to the downregulation of surface TCRs. In other systems, receptor downregulation can induce perfect adaptation to constant stimulation by a mechanism known as state-dependent inactivation that requires complete downregulation of the receptor or the ligand. However, this is not the case for the TCR, and therefore, precisely how TCR downregulation maintains or limits T cell responses is controversial. Here, we observed that in vitro expanded primary human T cells exhibit perfect adaptation in cytokine production to constant antigen stimulation across a 100,000-fold variation in affinity with partial TCR downregulation. By directly fitting a mechanistic model to the data, we show that TCR downregulation produces imperfect adaptation, but when coupled to a switch produces perfect adaptation in cytokine production. A pre-diction of the model is that pMHC-induced TCR signalling continues after adaptation and this is confirmed by showing that, while costimulation cannot prevent adaptation, CD28 and 4-1BB signalling reactivated adapted T cells to produce cytokines in a pMHC-dependent manner. We show that adaptation also applied to 1st generation chimeric antigen receptor (CAR)-T cells but is partially avoided in 2nd generation CARs. These findings high-light that even partial TCR downregulation can limit T cell responses by producing perfect adaptation rendering T cells dependent on costimulation for sustained responses.

immunology↗