Components of innate immunity that are active against viral cells include: March 2009
**Question:** Components of innate immunity that are active against viral cells include: March 2009
A. Natural Killer Cells
B. Antibodies
C. Complement System
D. Phagocytes
**Correct Answer:** D. Phagocytes
**Core Concept:** Innate immunity is the body's first line of defense against pathogens, including viruses. It is a non-specific defense mechanism that involves various cell types and molecules, collectively known as effector cells or effector molecules. In the context of the question, we are specifically discussing components that are active against viral cells.
**Why the Correct Answer is Right:** In the fight against viral infections, phagocytes, particularly macrophages and neutrophils, play a crucial role. These cells are part of the innate immune system and are crucial in recognizing and eliminating pathogens, including viruses, through phagocytosis, a process where the cell ingests and destroys the pathogen. Phagocytes release various antimicrobial substances, such as reactive oxygen species, reactive nitrogen species, and proteolytic enzymes, which directly damage the viral cells and inhibit their replication.
**Why Each Wrong Option is Incorrect:**
A. Natural Killer Cells (NK cells) are involved in the adaptive immune response and specifically target and kill virus-infected cells. While NK cells play a role in the immune response to viral infections, they do not directly target and destroy viruses like phagocytes do.
B. Antibodies, also known as immunoglobulins, are part of the adaptive immune response and are produced by B cells. They recognize and bind to specific viral antigens, marking infected cells for destruction by other immune cells. Antibodies are not involved in directly destroying viral cells.
C. Complement system is an essential part of the innate immune response. It consists of a group of proteins that function together to facilitate the clearance of pathogens, including viruses, by enhancing phagocytosis, inflammation, and direct pathogen destruction. However, complement system is not a cell type but a group of proteins.
**Clinical Pearl:** The innate immune system is the first line of defense against pathogens, including viruses, and phagocytes (macrophages and neutrophils) play a crucial role in directly destroying viruses through phagocytosis and releasing antimicrobial substances.
**Why Each Wrong Option is Incorrect:**
A. Natural Killer cells (NK cells) are part of the adaptive immune response and target and kill virus-infected cells, not viruses. Antibodies are produced by B cells and recognize specific viral antigens, marking infected cells for destruction by other immune cells. Complement system is a group of proteins involved in the innate immune response, enhancing phagocytosis, inflammation, and direct pathogen destruction.
**Clinical Pearl:** The innate immune system is the first line of defense against pathogens, including viruses, and phagocytes (macrophages and neutrophils) play a crucial role in directly destroying viruses through phagocytosis and releasing antimicrobial substances.