A missing PD-L1/PD-1 coinhibition regulates diabetes induction by preproinsulin-specific CD8 T-cells in an epitope-specific manner

PLoS One. 2013 Aug 19;8(8):e71746. doi: 10.1371/journal.pone.0071746. eCollection 2013.

Abstract

Coinhibitory PD-1/PD-L1 (B7-H1) interactions provide critical signals for the regulation of autoreactive T-cell responses. We established mouse models, expressing the costimulator molecule B7.1 (CD80) on pancreatic beta cells (RIP-B7.1 tg mice) or are deficient in coinhibitory PD-L1 or PD-1 molecules (PD-L1(-/-) and PD-1(-/-) mice), to study induction of preproinsulin (ppins)-specific CD8 T-cell responses and experimental autoimmune diabetes (EAD) by DNA-based immunization. RIP-B7.1 tg mice allowed us to identify two CD8 T-cell specificities: pCI/ppins DNA exclusively induced K(b)/A(12-21)-specific CD8 T-cells and EAD, whereas pCI/ppinsΔA(12-21) DNA (encoding ppins without the COOH-terminal A(12-21) epitope) elicited K(b)/B(22-29)-specific CD8 T-cells and EAD. Specific expression/processing of mutant ppinsΔA(12-21) (but not ppins) in non-beta cells, targeted by intramuscular DNA-injection, thus facilitated induction of K(b)/B(22-29)-specific CD8 T-cells. The A(12-21) epitope binds K(b) molecules with a very low avidity as compared with B(22-29). Interestingly, immunization of coinhibition-deficient PD-L1(-/-) or PD-1(-/-) mice with pCI/ppins induced K(b)/A(12-21)-monospecific CD8 T-cells and EAD but injections with pCI/ppinsΔA(12-21) did neither recruit K(b)/B(22-29)-specific CD8 T-cells into the pancreatic target tissue nor induce EAD. PpinsΔA(12-21)/(K(b)/B(22-29))-mediated EAD was efficiently restored in RIP-B7.1(+)/PD-L1(-/-) mice, differing from PD-L1(-/-) mice only in the tg B7.1 expression in beta cells. Alternatively, an ongoing beta cell destruction and tissue inflammation, initiated by ppins/(K(b)/A(12-21))-specific CD8 T-cells in pCI/ppins+pCI/ppinsΔA(12-21) co-immunized PD-L1(-/-) mice, facilitated the expansion of ppinsΔA(12-21)/(K(b)/B(22-29))-specific CD8 T-cells. CD8 T-cells specific for the high-affinity K(b)/B(22-29)- (but not the low-affinity K(b)/A(12-21))-epitope thus require stimulatory help from beta cells or inflamed islets to expand in PD-L1-deficient mice. The new PD-1/PD-L1 diabetes models may be valuable tools to study under well controlled experimental conditions distinct hierarchies of autoreactive CD8 T-cell responses, which trigger the initial steps of beta cell destruction or emerge during the pathogenic progression of EAD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens / metabolism
  • B7-H1 Antigen / antagonists & inhibitors*
  • B7-H1 Antigen / metabolism
  • Bystander Effect / immunology
  • CD8-Positive T-Lymphocytes / immunology*
  • Diabetes Mellitus, Experimental / immunology*
  • Diabetes Mellitus, Experimental / pathology*
  • Disease Models, Animal
  • Epitopes / immunology*
  • HEK293 Cells
  • Humans
  • Insulin / metabolism*
  • Mice
  • Mice, Transgenic
  • Mutation / genetics
  • Programmed Cell Death 1 Receptor / antagonists & inhibitors*
  • Programmed Cell Death 1 Receptor / metabolism
  • Protein Precursors / metabolism*

Substances

  • Antigens
  • B7-H1 Antigen
  • Cd274 protein, mouse
  • Epitopes
  • Insulin
  • Pdcd1 protein, mouse
  • Programmed Cell Death 1 Receptor
  • Protein Precursors
  • preproinsulin

Grants and funding

This work was supported by grants from the Deutsche Forschungsgemeinschaft: GRK-1041 (to R.S. and B.O.B.) and DFG SCHI-505/4-1 (to R.S.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.