Q.21 Which one of the following is NOT a principal component of innate immunity?
(A) Mucosal epithelia
(B) Dendritic cells
(C) Complement system
(D) Memory B-cells
Memory B-cells are not a principal component of innate immunity.
Innate immunity provides rapid, non-specific defense against pathogens, while adaptive immunity involves specific memory cells like Memory B-cells. This question tests the distinction between these two arms of the immune system.
Option Analysis
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(A) Mucosal epithelia: These form physical barriers lined with mucus that trap pathogens and secrete antimicrobial substances, serving as a key first line of innate immunity.
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(B) Dendritic cells: These act as sentinel cells that detect pathogens via pattern recognition receptors, phagocytose microbes, and initiate inflammation while bridging to adaptive responses.
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(C) Complement system: This group of serum proteins enhances phagocytosis (opsonization), lyses pathogens directly, and promotes inflammation, forming a core soluble mediator of innate immunity.
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(D) Memory B-cells: These arise from adaptive immunity after antigen-specific activation, providing long-term memory for faster secondary responses; they are absent in innate immunity, which lacks specificity and memory.
Innate immunity forms the body’s first line of defense against infections through rapid, non-specific mechanisms like barriers, cells, and proteins. Understanding principal components of innate immunity—such as mucosal epithelia, dendritic cells, and the complement system—helps distinguish it from adaptive immunity, which involves memory B-cells. This guide explains each option in the question “Which one of the following is NOT a principal component of innate immunity?” for students, researchers, and biotech professionals preparing for exams.
Key Components of Innate Immunity
Innate immunity activates within minutes of pathogen exposure, relying on:
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Physical barriers: Skin and mucosal epithelia prevent microbial entry.
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Cellular effectors: Phagocytes like dendritic cells and macrophages engulf invaders.
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Soluble factors: Complement system proteins amplify responses.
These elements contrast with adaptive immunity’s antigen-specific memory.
Detailed Option Breakdown
| Option | Role in Immunity | Innate or Adaptive? | Explanation |
|---|---|---|---|
| Mucosal epithelia | Traps pathogens in mucus | Innate | Principal barrier component. |
| Dendritic cells | Pathogen sensing and phagocytosis | Innate | Bridge innate to adaptive. |
| Complement system | Opsonization and lysis | Innate | Key humoral innate mediator. |
| Memory B-cells | Long-term antibody response | Adaptive | NOT innate; provides memory . |
Why Memory B-cells Are Excluded
Memory B-cells develop post-infection in adaptive immunity, enabling faster responses upon re-exposure. Innate immunity lacks this memory, confirming (D) as the correct answer. For molecular biology researchers, this highlights B-cell activation via germinal centers, absent in innate pathways.
