B7-1 mediated costimulation regulates pancreatic autoimmunity

Area of Science:

• Immunology
• Autoimmunity
• T-cell biology

Background:

• B7-1 and B7-2 costimulatory molecules have distinct roles in immune responses.
• In NOD mice, B7-2 deficiency protects against diabetes, while B7-1 deficiency exacerbates it.

Purpose of the Study:

• To investigate the hypothesis that B7-1 costimulation suppresses pancreatic autoimmunity.
• To elucidate the immunological defects caused by B7-1 deficiency.

Main Methods:

• Analysis of NOD mice with B7-1 deficiency (B7-1KO).
• Immunophenotypic analysis of T cells and antigen-presenting cells (APCs).
• Assessment of T-regulatory cell populations and T-cell expansion, survival, and effector function.
• Blocking studies using B7-H1.

Main Results:

• B7-1 deficiency leads to aberrant thymocyte maturation and enhanced expansion, survival, and effector function of islet-specific T cells.
• A significant reduction in T-regulatory cells was observed in B7-1KO mice.
• B7-1KO mice showed lower frequencies of PD-1 expressing T cells and higher frequencies of B7-H1 positive APCs.
• B7-H1 signaling negatively impacts anti-islet CD4 and CD8 T-cell expansion but is differentially required for priming.

Conclusions:

• Deficiency in B7-1 mediated costimulation results in multiple immunological defects.
• These defects include reduced T-regulatory cells and enhanced expansion, survival, and effector potential of autoreactive T cells.
• B7-1 plays a critical role in suppressing pancreatic autoimmunity.