Multiple Choice
Which of the following is a form of cell communication that may be used during an immune response?
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19. Innate Immunity
Introduction to Cell Communication
2:12 minutesProblem 8
Textbook Question
Which of the following is not targeted by a Toll-like receptor?
a. Lipid A
b. Eukaryotic flagellar protein
c. Single-stranded RNA
d. Lipoteichoic acid
Verified step by step guidance1
Step 1: Understand the role of Toll-like receptors (TLRs). TLRs are a class of proteins that recognize pathogen-associated molecular patterns (PAMPs) found on microbes, triggering an immune response.
Step 2: Identify common targets of TLRs. For example, TLR4 recognizes Lipid A (a component of lipopolysaccharide in Gram-negative bacteria), TLR2 recognizes lipoteichoic acid (from Gram-positive bacteria), and TLR7/8 recognize single-stranded RNA (common in viruses).
Step 3: Analyze each option in the question: (a) Lipid A is recognized by TLR4, (b) Eukaryotic flagellar protein is a protein from eukaryotes, not bacteria, so it is generally not recognized by TLRs, (c) Single-stranded RNA is recognized by TLR7/8, (d) Lipoteichoic acid is recognized by TLR2.
Step 4: Recall that TLRs primarily recognize microbial components, not eukaryotic proteins, so eukaryotic flagellar protein is not a target of TLRs.
Step 5: Conclude that the correct answer is the option that is not targeted by TLRs, which is the eukaryotic flagellar protein.
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Video duration:
2mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Toll-like Receptors (TLRs) and Their Function
TLRs are pattern recognition receptors in the innate immune system that detect conserved microbial molecules called pathogen-associated molecular patterns (PAMPs). They initiate immune responses by recognizing components like bacterial lipids, nucleic acids, and proteins, helping the body distinguish pathogens from self.
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Toll-Like Receptors
Common Ligands Recognized by TLRs
Different TLRs recognize specific microbial molecules: TLR4 detects Lipid A from Gram-negative bacteria; TLR2 recognizes lipoteichoic acid from Gram-positive bacteria; TLR7 and TLR8 detect single-stranded RNA from viruses. These interactions trigger signaling pathways to activate immune defenses.
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Distinction Between Prokaryotic and Eukaryotic Flagellar Proteins
Bacterial flagella are made of flagellin, a protein recognized by TLR5, whereas eukaryotic flagella have a different structure and protein composition. TLRs do not target eukaryotic flagellar proteins because they are not microbial PAMPs, thus preventing immune responses against host or non-pathogenic eukaryotic cells.
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