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NBME 21 Answers

nbme21/Block 1/Question#3

An investigator is studying the efficacy of ...


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submitted by cantaloupe5(37),

Capsular polysaccharide vaccines are often conjugated to proteins to improve immunogenicity. Flagellin is the only answer choice that's a protein.

I think they want you to think about how conjugate vaccine is made: polysaccharide + protein fragment (to induce T dependent immune response). Only flagellin is a protein (or at least sounds like one) in the option list.

vi_capsule  Flagellum is protein. Pilli/Fimbriae - GLycoprotein +1  

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submitted by enbeemee(5),

i get why it's flagellin, but is the specific reason that LPS is wrong is because it's just not how the vaccine is made? LPS would also elicit an immune reaction, right?

nor16  Lipid A of LPS can be sensed by CD14 of macrophages causing shock, its not a protein, so no immune reaction as in vaccination (humoral, IgG class switch via Th2 and B Cells). +2  
eclipse  actually they do use LPS as adjuvant in vaccines +1  
eclipse  actually they do use LPS as adjuvant in vaccines +1  
hyperfukus  TLRs recognize common motifs called pathogen-associated molecular pattern (PAMP) in bacteria, fungi, viruses, and other pathogens. TLR signaling in the modulation of innate immunity + adaptive immunity against pathogens, TLR agonists: CpG-DNA, flagellin, and lipid became essential candidates of effective+safe vaccine adjuvants. TLR agonists improve the efficacy of vaccine, reducing TCR-based selection thresholds and enhancing the magnitude and quality of memory T-cell response. +  
hyperfukus  some extra info in case they ask another annoying q +