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, or immunoglobulins, are glycoproteins produced by B cells as part of the adaptive immune response. Their primary functions include recognizing and binding to specific antigens, which are foreign substances such as pathogens (bacteria and viruses) or toxins. The main roles of antibodies in the immune system are to neutralize pathogens, facilitate their elimination, and enhance other immune responses.
- Neutralizing bacterial toxins (A): Antibodies can bind to toxins produced by bacteria, neutralizing their harmful effects. By preventing the toxin from interacting with host cells, antibodies help protect the body from damage that toxins could cause.
- Preventing viruses from entering tissue cells (B): Antibodies can also block viruses from attaching to and entering host cells. This is crucial because many viruses rely on specific receptors on host cells to gain entry. By binding to the virus, antibodies prevent it from infecting cells and replicating.
- Opsonizing foreign antigens (D): Opsonization is a process whereby antibodies coat foreign antigens, marking them for destruction by phagocytic cells such as macrophages and neutrophils. This enhances the efficiency of phagocytosis, allowing the immune system to more effectively eliminate pathogens.
- Direct cell killing through the release of toxic chemicals (C): This option is incorrect because antibodies themselves do not directly kill cells. Instead, they can activate other components of the immune system, such as the complement system or effector cells (e.g., cytotoxic T cells), which are responsible for the destruction of infected or malignant cells. While some immune responses involve the release of toxic substances, it is primarily the role of cytotoxic T cells or natural killer (NK) cells, rather than antibodies.
In summary, while antibodies play several crucial roles in the immune response, they do not directly kill cells through toxic chemical release, which distinguishes their functions from those of other immune cells involved in cell-mediated immunity.