Open AccessPS1302 THE CD58‐CD2 AXIS CONTROLS KILLING OF B CELLS BY CYTOTOXIC T CELLS
Author(s) -
Zurli V.,
Montecchi T.,
Wimmer G.,
Acuto O.,
Baldari C.T.,
Kabanova A.
Publication year - 2019
Publication title -
hemasphere
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 11
ISSN - 2572-9241
DOI - 10.1097/01.hs9.0000563488.72162.16
Subject(s) - cytotoxic t cell , raji cell , cd8 , cytotoxicity , microbiology and biotechnology , cd20 , antigen , antibody dependent cell mediated cytotoxicity , antibody , flow cytometry , t cell , cd3 , chemistry , immune system , immunology , biology , in vitro , monoclonal antibody , biochemistry
Background: Identification of costimulatory and signaling pathways enhancing the activity of cytotoxic T cells (CTLs) represents a major approach towards the development of tumour immunotherapies. To exert their vital function, CTLs polarize and focally release lytic granules at the immune synapse formed with their targets. We previously reported that tumour B cells can resist CTL killing by establishing dysfunctional synapses characterized by non‐polarized granule release. Aims: In the current work we aimed to identify the mechanism for such resistance and perform an in‐depth analysis of signaling pathways involved. Methods: Firstly, by applying comparative proteomics analysis of surface proteins to a panel of B cells, we identified that CD58 levels determine the susceptibility of B cells to CTL lysis. Then we used CRISPR/Cas9 technology, functional assays, and phospho‐proteomics to characterize the underlying mechanism. Results: We demonstrate that CD58 binding to the receptor CD2 of CTLs has a unique relevance to B cell killing, compared to other costimulatory pathways, such as the ones elicited by LFA‐1, SLAMF1, SLAMF7 or CD30 ligand. CD2 costimulation plays a central role in the formation of functional lytic synapses between human CTLs and B cell targets. CD2 not only promotes synapse formation but is also directly responsible for the polarization of lytic granules towards the synaptic interface. To broadly explore the CD2 signaling network, we undertook a global analysis of protein phosphorylation in CD2‐stimulated CTLs, which revealed 423 unique phosphosites on 376 proteins. CD2 stimulation elicited an intricated network of signaling events regulating T cell metabolism, autophagy, vesicular trafficking, cell polarity and cytoskeleton organization. We further identify a functionally critical node of this network, belonging to the mTOR signaling pathway, which regulates targeted granule secretion in human CTLs. Summary/Conclusion: Our results thus establish the central role of CD58‐CD2 axis in the regulation of B cell killing by CTLs. Moreover, considering that loss of CD58 expression on B‐cell tumours has been described as the mechanism of cancer progression, our results are expected to be valuable for the development of focused therapies counteracting cancer immune evasion.