NBME 21 Flagellin (NBME Answers)

NBME 21 Answers

nbme21/Block 1/Question#3 (reveal difficulty score)
An investigator is studying the efficacy of ...
Flagellin 🔍 / 📺 / 🌳 / 📖
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submitted by ∗cantaloupe5(87)

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

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mambaforstep both MHC 1 and 2 are present antigens that are PROTEINS (FA 2019 pg 100). so in order to elicit a T cell response, you need a protein (CANT BE A POLYSACC). that is why vaccines for polysaccaride antigens are often conjugated to PROTEINs--> so that we can elicit a T-cell response (FA 2019 pg 127). +7

lovebug Flagellum = Protein, (FA19, pg.124) +1

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submitted by ∗wasabilateral(47)

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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.

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vi_capsule Flagellum is protein. Pilli/Fimbriae - GLycoprotein +4

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submitted by enbeemee(12)

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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?

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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). +4

eclipse actually they do use LPS as adjuvant in vaccines +3

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. +5

hyperfukus some extra info in case they ask another annoying q +5

aturner713 Not sure if this matters for this or not, but Neisseria spp. have lipoOLIGOsaccharide (LOS) and not lipoPOLYsaccharide (LPS) +5

schep I don't understand why LPS couldn't be the answer also. UWorld question ID 45 specifically says that they are using LPS as a conjugate +1

jp1003 I think it's because Neisseria does have LPS. They have LOS instead. +2

jp1003 *does not have LPS +2

thrawn Doesnt matter - we dont necessarily inject the same specie LOS/LPS in a vaccine - anything to make the immune system wake up to a threat +1

an1 The term lipooligosaccharide ("LOS") is used to refer to a low-molecular-weight form of bacterial lipopolysaccharides. But injecting LPS will induce shock and the 'ENDOTOXIN" cascade mentioned in FA +1

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