Journal
FRONTIERS IN IMMUNOLOGY
Volume 11, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fimmu.2020.600000
Keywords
regulatory T cells; costimulation; CD86; CD80; CTLA-4; homeostasis; CD28
Categories
Funding
- Wellcome Trust Clinical PhD studentship award [110297/Z/15/Z]
- Arthritis Research UK [21147]
- BBSRC iCASE studentship with UCB Pharma
- Wellcome Trust [20478/Z/16, 204798/Z/16/Z]
- National Institutes of Health Research (NIHR) University College London Biomedical Research Centre fund
- NIHR Rare Disease Translational Research Collaboration
- MRC [MR/N001435/1]
- Wellcome Trust [204798/Z/16/Z, 110297/Z/15/Z] Funding Source: Wellcome Trust
- Biotechnology and Biological Sciences Research Council [BB/M009203/1, 1497411] Funding Source: researchfish
- Medical Research Council [MR/N001435/1] Funding Source: researchfish
- Versus Arthritis [21147] Funding Source: researchfish
- MRC [MR/N001435/1] Funding Source: UKRI
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CD80 and CD86 are expressed on antigen presenting cells and are required to engage their shared receptor, CD28, for the costimulation of CD4 T cells. It is unclear why two stimulatory ligands with overlapping roles have evolved. CD80 and CD86 also bind the regulatory molecule CTLA-4. We explored the role of CD80 and CD86 in the homeostasis and proliferation of CD4+FoxP3+ regulatory T cells (Treg), which constitutively express high levels of CTLA-4 yet are critically dependent upon CD28 signals. We observed that CD86 was the dominant ligand for Treg proliferation, survival, and maintenance of a regulatory phenotype, with higher expression of CTLA-4, ICOS, and OX40. We also explored whether CD80-CD28 interactions were specifically compromised by CTLA-4 and found that antibody blockade, clinical deficiency of CTLA-4 and CRISPR-Cas9 deletion of CTLA-4 all improved Treg survival following CD80 stimulation. Taken together, our data suggest that CD86 is the dominant costimulatory ligand for Treg homeostasis, despite its lower affinity for CD28, because CD80-CD28 interactions are selectively impaired by the high levels of CTLA-4. These data suggest a cell intrinsic role for CTLA-4 in regulating CD28 costimulation by direct competition for CD80, and indicate that that CD80 and CD86 have discrete roles in CD28 costimulation of CD4 T cells in the presence of high levels of CTLA-4.
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