Two different forms of inherited human TCRα chain deficiency

Area of Science:

• Immunology
• Genetics

Background:

• Severe combined immunodeficiency (SCID) is a life-threatening condition caused by the absence of all T cells.
• T cell receptor (TCR) alpha (TRAC) gene defects can lead to varying T cell deficiencies.

Purpose of the Study:

• To investigate the clinical and molecular consequences of complete TRAC deficiency.
• To clarify the role of alpha-beta (αβ) T cells in human immunity.

Main Methods:

• Described two children with biallelic premature stop codons in TRAC.
• Performed in vitro analysis of a previously reported TRAC variant.

Main Results:

• Complete TRAC deficiency resulted in a lack of αβ T cells, severe immunodeficiency, and early death.
• A previously identified TRAC variant showed partial activity, allowing low-level functional TCRαβ expression, correlating with milder phenotypes and longer survival.

Conclusions:

• Complete absence of TCRα leads to a SCID-like presentation.
• Partial TCRα deficiency is associated with less severe clinical outcomes, underscoring the non-redundant role of αβ T cells.