Lower receptor avidity required for thymic clonal deletion than for effector T-cell function.

Area of Science:

• Immunology
• T-cell biology
• Self-tolerance

Background:

• Clonal deletion in the thymus is crucial for T-cell tolerance to self-antigens.
• The precise mechanisms, specificity, and affinity/avidity thresholds of negative selection remain incompletely understood.

Purpose of the Study:

• To investigate the fine specificity and affinity/avidity thresholds of T-cell receptor (TCR)-mediated negative selection.
• To elucidate the relationship between TCR interaction strength and T-cell responses (deletion vs. activation).

Main Methods:

• Utilized transgenic mice expressing a TCR specific for lymphocytic choriomeningitis virus (LCMV) glycoprotein/H-2Db.
• Induced tolerance to LCMV via neonatal infection with mutant LCMVs altering the T-cell epitope.
• Assessed T-cell deletion in the thymus and antiviral responses in vivo and in vitro.

Main Results:

• Neonatal tolerance induction was achieved using mutant LCMVs.
• A low-avidity TCR-antigen interaction was sufficient for clonal deletion in the thymus.
• This same low-avidity interaction failed to induce effector T-cell responses in the periphery.

Conclusions:

• Negative selection in the thymus operates at a lower affinity/avidity threshold than T-cell activation.
• This differential threshold allows for the elimination of potentially self-reactive T cells while preserving responses to foreign antigens.
• Fine-tuning of T-cell responses is achieved through distinct avidity requirements for thymic deletion and peripheral activation.