Lymphocyte Activation Gene (LAG)-3 Is Associated With Mucosal Inflammation and Disease Activity in Ulcerative Colitis

Abstract

Background and Aims Lymphocyte activation gene [LAG]-3 is an immune checkpoint and its expression identifies recently activated lymphocytes that may contribute to inflammation. We investigated the role of LAG-3 by analysing its expression and function in immune cells from blood and tissue of patients with ulcerative colitis [UC]. Methods The phenotypic properties of LAG-3+ T cells were determined by flow cytometry, qRT-PCR and single-cell RNA-sequencing. LAG-3+ cells were quantified and correlated with disease activity. The functional effects of LAG-3+ cells were tested using a depleting anti-LAG-3 monoclonal antibody [mAb] in a mixed lymphocyte reaction [MLR]. Results LAG-3+ cells in the blood were negligible. LAG-3+ lymphocytes were markedly increased in inflamed mucosal tissue and both frequencies of LAG-3+ T cells and transcript levels of LAG3 correlated with endoscopic severity. LAG-3 expression was predominantly on effector memory T cells, and single-cell RNA-sequencing revealed LAG3 expression in activated and cytokine-producing T cell subsets. Foxp3+CD25hi Tregs also expressed LAG-3, although most mucosal Tregs were LAG-3−. Mucosal LAG-3+ cells produced mainly interferon γ [IFNγ] and interleukin-17A. LAG-3+ cell numbers decreased in patients who responded to biologics, and remained elevated in non-responders. Treatment with a depleting anti-LAG-3 mAb led to a reduction in proliferation and IFNγ production in an MLR. Conclusions LAG-3+ cells are increased in the inflamed mucosa, predominantly on effector memory T cells with an activated phenotype and their cell numbers positively correlate with disease activity. Depleting LAG-3 eliminates activated proliferating T cells, and hence LAG-3 could be a therapeutic target in UC.

A Multi-Omics Analysis of Mucosal-Associated-Invariant T Cells Reveals Key Drivers of Distinct Modes of Activation

“…Lymphocyte-activation gene (LAG)-3, the key protein of the third cluster, was significantly more abundant only after combined TCR-dependent and independent activation. LAG-3 is a transmembrane receptor and has been shown earlier to be activated in T cells following TCR and/or cytokine stimulation, promoting IFN-y, TNF or IL-12 production ( 80 , 81 ). LAG-3 is a co-inhibitory receptor, which binds to MHC class II on antigen-presenting cells in order to suppress further T cell activation and cytokine secretion, preventing excessive inflammation and facilitating a state of immune homeostasis ( 82 ).…”

“…LAG3 expression in conventional T cells renders them susceptible to regulatory T cell subsets and affects differentiation ( 83 ). In patients with inflammatory bowel disease, LAG-3 expressing T cells are primarily found at sites of mucosal inflammation and their numbers correlate with disease activity ( 80 ). LAG-3 expression was accompanied by high IFN-γ concentration in activated MAIT cells, as previously shown for conventional T helper cells ( 84 ), suggesting that circulating soluble LAG-3, as well as associated proteins, e.g., STAT4 or IRF4, may be employed as a promising biomarker of MAIT cell activation and disease activity in UC.…”

Depletion of LAG‐3+ T Cells Translated to Pharmacology and Improvement in Psoriasis Disease Activity: A Phase I Randomized Study of mAb GSK2831781

“…This clinical study is the first to report the pharmacology and clinical improvement in psoriasis disease activity following the targeted depletion of immune cells expressing LAG‐3 (a negative regulator) as a marker of recent cell activation using a novel mAb GSK2831781. The role of LAG‐3 + T cells in autoimmune disease is incompletely understood but relatively higher LAG‐3 expression in tissues (as compared with blood) is a marker of pathogenic autoreactive T cells that are chronically activated 12 . Given the interest in manipulating LAG‐3 in both oncology and autoinflammatory diseases, its function and impact is of considerable scientific interest.…”

Understanding LAG-3 Signaling

“…LAG-3 can be upregulated under various antigen stimulation conditions [ 3 , 8 , 9 ]. Its expression is induced by TCR stimulation or cytokine stimulation, and LAG-3 is upregulated within activated, cytokine-expressing T cells [ 9 , 10 , 11 , 12 ]. LAG-3 associates with the TCR:CD3 complex at the T cell membrane and negatively regulates TCR signal transduction, which in turn terminates cell proliferation and cytokine secretion in response to CD3 signaling [ 13 ].…”

“…In addition, LAG-3 + -regulatory T cells are required to suppress the inflammatory activities of CX3CR1 + macrophages to maintain tissue homeostasis during lymphoid cell-driven colitis [ 99 ]. Moreover, LAG-3 + cells have been shown to be increased in the inflamed mucosa and correlate with endoscopic severity and disease phenotype in ulcerative colitis [ 12 ].…”