Which of the following is not a function of antibodies?
A) Neutralizing bacterial toxins
B) Preventing viruses from entering tissue cells
C) Direct cell killing through the release of toxic chemicals
D) Opsonizing foreign antigen
The Correct Answer and Explanation is:
The correct answer is C) Direct cell killing through the release of toxic chemicals.
Explanation
Antibodies, also known as immunoglobulins, play a vital role in the immune system by identifying and neutralizing pathogens such as bacteria and viruses. They are produced by B cells and are crucial for humoral immunity. While antibodies have various functions, direct cell killing is not one of them.
- Neutralizing Bacterial Toxins (A): Antibodies can bind to toxins produced by bacteria, neutralizing their harmful effects. This process prevents the toxins from interacting with host cells and causing damage, effectively mitigating the threat posed by bacterial infections.
- Preventing Viruses from Entering Tissue Cells (B): Antibodies can also prevent viruses from entering cells. They do this by binding to viral particles, blocking their ability to attach to and penetrate host cells. This neutralization is critical in stopping viral infections before they can establish themselves within the host.
- Opsonizing Foreign Antigen (D): Opsonization is a process by which antibodies coat pathogens, marking them for destruction by phagocytic cells such as macrophages and neutrophils. This enhancement of phagocytosis is crucial for eliminating foreign antigens from the body.
- Direct Cell Killing (C): Unlike cytotoxic T cells, which are capable of directly killing infected or cancerous cells, antibodies do not have the mechanism to induce direct cell death. Instead, they function primarily through neutralization, opsonization, and activation of the complement system, which enhances the ability of immune cells to clear pathogens. The role of antibodies is more about marking and neutralizing threats rather than executing direct cytotoxicity.
In summary, while antibodies have diverse functions in immune defense, direct cell killing through the release of toxic chemicals is not one of them. This function is more characteristic of certain immune cells, particularly cytotoxic T cells and natural killer (NK) cells, which actively kill infected or abnormal cells.