Inherited and somatic CD3zeta mutations in a patient with T-cell deficiency

Area of Science:

• Immunology
• Genetics
• Molecular Biology

Background:

• Primary immunodeficiencies (PIDs) are a group of genetic disorders affecting the immune system.
• The T-cell receptor-CD3 (TCR-CD3) complex is essential for T-cell development, function, and immune response.
• CD3zeta (CD247) is a critical component of the TCR-CD3 complex, mediating signal transduction.

Observation:

• A four-month-old boy presented with a severe primary immunodeficiency.
• Genetic analysis identified a homozygous germ-line mutation (Q70X) in the gene encoding CD3zeta.
• The patient exhibited distinct T-cell populations: some with low TCR-CD3 levels and homozygous Q70X mutations, others with normal TCR-CD3 levels and one Q70X allele plus a heterozygous somatic mutation on the other allele.

Findings:

• The homozygous germ-line Q70X mutation in CD3zeta impairs T-cell development and function.
• Somatic mosaicism, involving heterozygous mutations in CD3zeta, allowed for the expression of partially functional TCR-CD3 complexes in a subset of T cells.
• This mosaicism resulted in T cells with varying levels of TCR-CD3 expression and signaling capacity.

Implications:

• This case highlights the role of CD3zeta in T-cell homeostasis and immune competence.
• Understanding the impact of germ-line and somatic mutations in CD3zeta provides insights into PID pathogenesis.
• The findings may inform diagnostic strategies and potential therapeutic interventions for T-cell defects involving the TCR-CD3 complex.