Down's syndrome: problems of immunodeficiency

Area of Science:

• Immunology
• Genetics
• Developmental Biology

Background:

• Down syndrome (DS) is characterized by increased susceptibility to infections, malignancies, and autoimmune disorders.
• Laboratory and pathological findings indicate an underlying immunodeficiency in individuals with DS.
• Reduced T-lymphocyte counts and impaired proliferative responses are observed, particularly with age.

Purpose of the Study:

• To investigate the underlying causes of immunodeficiency in Down syndrome.
• To explore the role of the thymus and thymic hormones in T-lymphocyte differentiation in DS.
• To identify potential defects in thymic epithelial cells contributing to immune dysfunction.

Main Methods:

• Analysis of circulating T-lymphocyte percentages.
• Assessment of lymphocyte proliferative response to mitogens.
• Evaluation of thymus morphology and serum thymic hormone levels.
• Investigation of thymic epithelial cell function.

Main Results:

• Subjects with DS show low T-lymphocyte percentages from birth.
• Lymphocyte response to mitogens declines significantly after the first decade of life.
• The thymus in DS subjects is morphologically abnormal, with low serum thymic hormone levels detected.
• Evidence suggests impaired T-lymphocyte maturation in DS.

Conclusions:

• The immunodeficiency in Down syndrome is likely linked to impaired T-lymphocyte maturation.
• A primary defect in thymic epithelial cells, affecting hormone synthesis or secretion, is proposed.
• This defect may hinder the necessary differentiation of T-lymphocytes, leading to immune dysfunction in DS.