Q.1 Which of the following is involved in innate immune response in higher
mammals?
(A) T cell antigen receptor
(B) B cell antigen receptor
(C) Toll-like receptor
(D) Major histocompatibility complex-II molecule
Innate Immune Response in Higher Mammals: Toll-Like Receptors Explained
Toll-like receptors (TLRs) are key players in the innate immune response of higher mammals, recognizing pathogen-associated molecular patterns to trigger rapid defense mechanisms. This article breaks down a common multiple-choice question on the topic, highlighting why option (C) Toll-like receptor is correct while explaining the roles of other options.
Correct Answer
The correct answer is (C) Toll-like receptor. TLRs serve as pattern recognition receptors on innate immune cells like macrophages and dendritic cells, initiating immediate responses such as inflammation and cytokine production without prior antigen exposure.
Option Breakdown
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(A) T cell antigen receptor: This receptor is specific to adaptive immunity, enabling T cells to recognize antigens presented by MHC molecules during acquired responses, not innate immunity.
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(B) B cell antigen receptor: Known as the B-cell receptor (BCR) or surface immunoglobulin, it functions in adaptive humoral immunity for antibody production, requiring antigen-specific activation.
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(C) Toll-like receptor: Directly involved in innate immunity by detecting microbial components like LPS or viral RNA, leading to NF-κB activation and proinflammatory signals in mammals.
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(D) Major histocompatibility complex-II molecule: MHC-II presents antigens to CD4+ T cells in adaptive immunity, primarily on professional antigen-presenting cells, bridging innate and adaptive phases but not initiating innate responses itself.
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Innate vs Adaptive Immunity
Innate immunity provides the first line of defense through non-specific mechanisms like TLR signaling, complement activation, and phagocytosis. Adaptive immunity, involving T and B cell receptors plus MHC-II, develops specificity and memory over days.
