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NBME 21 Answers

nbme21/Block 1/Question#3 (53.1 difficulty score)
An investigator is studying the efficacy of ...

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 +19  upvote downvote
submitted by cantaloupe5(68),
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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). +3  
lovebug  Flagellum = Protein, (FA19, pg.124) +  

 +6  upvote downvote
submitted by enbeemee(13),
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i egt wyh st'i i,nfgellal but si eth fpceisci soraen ahtt PSL is rgnwo is bseeuac t'is usjt ton ohw eth encacvi is me?da PLS ouldw olas itceli an mienum c,raointe ?igtrh

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. +2  
hyperfukus  some extra info in case they ask another annoying q +3  
aturner713  Not sure if this matters for this or not, but Neisseria spp. have lipoOLIGOsaccharide (LOS) and not lipoPOLYsaccharide (LPS) +1  

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vi_capsule  Flagellum is protein. Pilli/Fimbriae - GLycoprotein +2