Biology subjects

Morgan, D. J.

Publications and source records attributed to Morgan, D. J..

4 recordsLinked to original sources

bioRxiv2023

TIM3 is a context-dependent co-regulator of cytotoxic T cell function

TIM3 is a co-regulatory receptor that is highly expressed on multiple immune cell types, including on T cells after prolonged exposure to antigen. It marks functionally suppressed cytotoxic T lymphocytes (CTL) in the tumor microenvironment. However, it is unresolved whether TIM3 acts directly on suppressed CTL. Moreover, the nature of TIM3 ligands remains controversial. Paradoxically, TIM3 combines inhibitory function in vivo with costimulatory signaling capability in vitro. Here we have investigated TIM3 in the direct interaction of suppressed murine and human CTL with tumor target cell using spheroids. TIM3 directly inhibited the function of such CTL. TIM3 regulated the ability of suppressed CTL to polarize their cytoskeleton as a required step in cytolysis. Expression of CEACAM1 in cis, on the CTL, blocked TIM3 function, expression of CEACAM1 and galectin9 in trans, on the tumor target cells, enhanced TIM3 function. TIM3 only functioned as an inhibitory receptor on the spheroid-suppressed CTL, not on active CTL in a two-dimensional tissue culture model. These data suggest that TIM3 amplifies T cell function, serving as a co-inhibitory or co-stimulatory receptor depending on the functional context of the T cell it is expressed on.

immunology↗

bioRxiv2022

Confocal reflectance microscopy for mapping collagen fiber organization in the vitreous gel of the eye

Vitreous collagen structure plays an important role in ocular mechanics, but capturing this structure with existing vitreous imaging methods is hindered by loss of sample position and orientation, low resolution, or small field of view. The objective of this study was to evaluate confocal reflectance microscopy as a solution to these limitations. The use of intrinsic reflectance avoids staining and optical sectioning eliminates the requirement for thin sectioning, minimizing processing for optimal preservation of natural structure. We developed a sample preparation and imaging strategy using ex vivo grossly sectioned porcine eyes. Imaging revealed a network of uniform diameter crossing fibers (1.1 {+/-} 0.3 m for a typical image) with generally poor alignment (alignment coefficient = 0.40 {+/-} 0.21 for a typical image). To test the utility of our approach for detecting differences in fiber spatial distribution, we imaged eyes every 1 mm along an anterior-posterior axis originating at the limbus and quantified the number of fibers in each image. Fiber density was higher anteriorly near the vitreous base, regardless of imaging plane. These data demonstrate that confocal reflectance microscopy addresses the previously unmet need for a robust, micron-scale technique to map features of collagen networks in situ across the vitreous.

biochemistry↗

bioRxiv2021

The adenosine 2a receptor and TIM3 directly inhibit killing of tumor cells by cytotoxic T lymphocytes through interference with cytoskeletal polarization

Tumors generate an immune-suppressive environment that prevents effective killing of tumor cells by CD8+ cytotoxic T cells (CTL). It remains largely unclear upon which cell type and at which stage of the anti-tumor response mediators of suppression act. We have combined an in vivo tumor model with a matching in vitro reconstruction of the tumor microenvironment based on tumor spheroids to identify suppressors of anti-tumor immunity that directly act on interaction between CTL and tumor cells and to determine mechanisms of action. An adenosine 2a receptor antagonist, as enhanced by blockade of TIM3, slowed tumor growth in vivo. Engagement of the adenosine 2a receptor and TIM3 reduced tumor cell killing in spheroids, impaired CTL cytoskeletal polarization ex vivo and in vitro and inhibited CTL infiltration into tumors and spheroids. With this focus on CTL killing, blocking A2aR and TIM3 complements therapies that enhance T cell priming, e.g. anti-PD1 and anti-CTLA-4.

immunology↗

bioRxiv2018

PD-1 suppresses the maintenance of cell couples between cytotoxic T cells and tumor target cells within the tumor

CD8+ T cell killing of tumor cells is suppressed by the tumor microenvironment. Inhibitory receptors, prominently PD-1, are key mediators of this suppression. To discover cellular defects triggered by tumor exposure and associated PD-1 signaling, we have established an ex vivo imaging approach to investigate CD8+ tumor infiltrating lymphocytes (TILs) interacting with tumor targets. Whilst TIL:tumor cell couples formed effectively, couple stability deteriorated within 1-2 minutes. This was associated with excessive cofilin recruitment to the cellular interface, coincident deterioration of f-actin structures, increased TIL locomotion, and impaired tumor cell killing. Diminished engagement of PD-1 within the tumor, but not acute ex vivo blockade, partially restored cell couple maintenance and killing. PD-1 thus suppresses TIL function by inducing a polarization-impaired state.

immunology↗