Which condition is an example of a congenital cell-mediated (T-cell) immunodeficiency?

• A. X-linked hypogammaglobulinemia
• B. DiGeorge's Syndrome
• C. Severe combined immunodeficiency syndrome
• D. AIDS

Answer: (B)

DiGeorge's Syndrome is a well-defined congenital immunodeficiency characterized by the underdevelopment or absence of the thymus gland, which is critical for the development and maturation of T-cells. This condition results from a deletion on chromosome 22 and leads to a specific deficit in T-cell mediated immunity. Individuals with DiGeorge's Syndrome often exhibit a range of symptoms, including heart defects, facial abnormalities, and hypoparathyroidism, alongside their immunodeficiency.

In this syndrome, because T-cells are essential for cell-mediated immunity, the absence or dysfunction of the thymus severely impacts the body’s ability to mount appropriate immune responses. Therefore, it exemplifies a congenital T-cell deficiency, as the impairment is inherent from birth due to genetic factors.

Other conditions listed, while they involve problems with the immune system, do not specifically represent congenital T-cell immunodeficiencies. For instance, X-linked hypogammaglobulinemia refers to a B-cell deficiency rather than a T-cell issue. Severe combined immunodeficiency syndrome (SCID) includes both B and T-cell defects, but it is more broadly classified as a combined immunodeficiency rather than being isolated to T-cells. AIDS is an acquired immunodeficiency caused