T lymphocytes are responsible for:
A.
Humoral immunity.
B.
Cell-mediated immunity.
C.
Programming macrophages.
D.
Producing antibodies.
The Correct Answer and Explanation is :
The correct answer is B. Cell-mediated immunity.
Explanation:
T lymphocytes, or T cells, are a type of white blood cell that plays a central role in the immune system, specifically in cell-mediated immunity. Cell-mediated immunity is one aspect of the adaptive immune system, which does not involve antibodies. Instead, it relies on the activation of T cells to directly attack and destroy infected or abnormal cells, such as those infected by viruses or transformed into cancerous cells.
There are several types of T lymphocytes, each with a specific role in cell-mediated immunity:
- Helper T cells (CD4+ T cells): These cells are crucial for coordinating the immune response. They release cytokines, which are signaling molecules that help activate and direct other immune cells, including macrophages, B cells, and cytotoxic T cells.
- Cytotoxic T cells (CD8+ T cells): These cells directly attack and destroy infected or abnormal cells. They recognize and bind to specific antigens presented by infected cells and release substances like perforins and granzymes, which induce cell death in the target cell.
- Regulatory T cells (Tregs): These cells help modulate the immune response, preventing excessive immune reactions that could lead to tissue damage or autoimmune disorders.
T cells recognize foreign antigens that are presented on the surface of infected cells by major histocompatibility complex (MHC) molecules. This recognition is essential for targeting infected cells specifically.
In contrast to T lymphocytes, B lymphocytes are responsible for humoral immunity (answer A), which involves the production of antibodies (answer D) to neutralize pathogens. Programming macrophages (answer C) is a function of helper T cells, but it is not the primary role of T lymphocytes in immunity.
Thus, T lymphocytes are essential for controlling intracellular infections and tumor cells through cell-mediated immunity.