Decreased T cell immunity is a feature of –
**Core Concept**
Decreased T cell immunity is a hallmark of immunodeficiency disorders that affect the development, maturation, or function of T lymphocytes. T cells play a crucial role in cell-mediated immunity, and their dysfunction can lead to recurrent infections, autoimmune diseases, or cancer.
**Why the Correct Answer is Right**
The correct answer is related to DiGeorge Syndrome, a congenital disorder characterized by thymic hypoplasia or aplasia. This leads to a reduction in the number of T cells, particularly CD4+ and CD8+ T cells, due to the impaired development of T cell progenitors in the thymus. The thymus is essential for T cell maturation, and its dysfunction results in a significant decrease in T cell immunity.
**Why Each Wrong Option is Incorrect**
* **Option A:** HIV infection primarily targets CD4+ T cells, but it does not affect the development or maturation of T cells. Instead, it causes a selective depletion of CD4+ T cells through viral replication and apoptosis.
* **Option B:** Severe Combined Immunodeficiency (SCID) is a group of disorders characterized by a deficiency in both T and B cell immunity. While SCID does involve decreased T cell immunity, it also affects B cell function and is not specific to T cell development or maturation.
* **Option C:** Systemic Lupus Erythematosus (SLE) is an autoimmune disease that can affect multiple organs and tissues. While SLE can cause T cell dysfunction and decreased T cell immunity, it is not a primary disorder of T cell development or maturation.
**Clinical Pearl / High-Yield Fact**
The thymus is essential for T cell maturation, and its dysfunction can lead to decreased T cell immunity. DiGeorge Syndrome is a classic example of a congenital disorder that affects T cell development and maturation, resulting in significant immunodeficiency.
**Correct Answer:** D. DiGeorge Syndrome