T-cell promiscuity in autoimmune diabetes

Area of Science:

• Immunology
• Autoimmunity
• Type 1 Diabetes Research

Background:

• T-cells are key mediators of beta-cell destruction in type 1 diabetes.
• The precise molecular recognition of beta-cell autoantigens by pathogenic T-cells is not fully understood.

Purpose of the Study:

• To investigate the properties of T-cell receptors (TCRs) specific for beta-cell antigens.
• To explore the fine specificity, functional avidity, and diabetogenicity of GAD65-specific CD4(+) T-cell clones in NOD mice.

Main Methods:

• Characterization of GAD65-specific CD4(+) T-cell clones from unimmunized NOD female mice at 4 and 14 weeks of age.
• Analysis of T-cell clone specificity, functional avidity, TCR binding affinity, and diabetogenicity via adoptive transfer.

Main Results:

• GAD65-specific T-cells predominantly recognized epitopes within amino acid regions 217-236 and 290-309.
• A significant proportion (31%) of T-cell clones from 14-week-old NOD mice exhibited dual specificity for both epitopes, mediated by a single TCR.
• These promiscuous T-cell clones displayed higher functional avidity and TCR binding affinity, leading to increased islet infiltration.

Conclusions:

• Promiscuous recognition of GAD65 epitopes contributes to the development of pathogenic CD4(+) T-cell clones in NOD mice.
• T-cell promiscuity represents a novel mechanism of T-cell avidity maturation in autoimmunity.