Beyond type 1 regulatory T cells: co-expression of LAG3 and CD49b in IL-10-producing T cell lineages

Weishan Huang; Sabrina Solouki; Chavez Carter; Song-Guo Zheng; Avery August

The mammalian immune system has evolved both effector and regulatory immune axes 48 to protect the host from invading pathogens, along with a control mechanism to tune the level of 49 immune reactivity against self-and non-self-agents to prevent host tissue damage. Interleukin- Therefore, Tr1 cells have strong promise as a potential therapeutic approach for inflammatory 68 diseases. Tr1 cells can be differentiated from naïve CD4 + T cells upon TCR engagement in the 69 presence of IL-27 in vitro [28] , and in order to identify and obtain viable Tr1 cells for clinical 70 application, co-expression of LAG3 and CD49b has been recently proposed to be cell surface 71 signature of the Foxp3 -IL-10 high Tr1 cells [15] . LAG3 is a structural homolog of CD4 molecule and 72 . CC-BY-ND 4.0 International license is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. It . https://doi.org/10.1101/359547 doi: bioRxiv preprint 5 can bind to MHC class II with high affinity [29; 30]. LAG3 is highly expressed by IL-10 + CD4 + T 73 cells [31] , as well as by activated effector T cells [32] and Foxp3 + Treg cells [33] . CD49b is the 2 74 integrin subunit, highly expressed by NK cells [34] . CD49b is up-regulated in T cells that may 75 produce IL-10 and/or pro-inflammatory cytokines [35; 36; 37] . In addition to Foxp3 -Tr1 cells, IL-76 10 can be highly up-regulated in activated Foxp3 + Treg and CD8 + T cells under inflammatory 77 conditions and/or upon TCR activation. Given the importance of being able to identify Foxp3 -Tr1 78 cells, including under clinical conditions, and to gain a better understanding of the specificity of 79 co-expression of LAG3 and CD49b as a cell surface signature for IL-10-producing cells, we 80 sought to determine whether co-expression of LAG3 and CD49b can mark broader range of T 81 cell subsets that are actively producing high levels of IL-10. 82 Using a murine model carrying an IL-10 GFP /Foxp3 RFP dual reporter system, we find that 83 co-expression of LAG3 and CD49b is a generic feature of the IL-10-producing Foxp3 -CD4 + , 84