Partial purine nucleoside phosphorylase deficiency. Studies of lymphocyte function

Area of Science:

• Immunology
• Biochemistry

Background:

• Purine nucleoside phosphorylase (PNP) deficiency is a rare genetic disorder.
• It primarily affects T-lymphocyte maturation and function, leading to immunodeficiency.

Observation:

• Two brothers with PNP deficiency presented with recurrent infections and lymphopenia.
• Cell-mediated immunity was impaired, showing absent delayed cutaneous reactivity and reduced lymphocyte proliferation.
• E-rosetting cells were decreased, but B-cell function and antibody production were normal.

Findings:

• Patients exhibited selective defects in T-cell function, including impaired responses to mitogens and antigens.
• Initial T-cell generation appeared intact, suggesting a defect in later T-cell maturation or function.
• In vitro attempts to restore lymphocyte responses were unsuccessful, even with purine nucleoside phosphorylase.

Implications:

• Partial PNP deficiency may result in a less severe clinical phenotype than complete deficiency.
• Understanding the specific T-cell defects aids in diagnosing and managing immunodeficiency disorders.
• This study highlights the critical role of purine metabolism in T-cell immunity.