WBR0683
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | |
| Sub Category | |
| Prompt | [[Prompt::Bacterial antigens are responsible for the stimulation of the innate immune system. Nonetheless, several organisms may evade the body's immunity via antigen variation. Which of the following antigenic variations is true about Salmonella enterica species?]] |
| Answer A | AnswerA::S. enterica alternatively expresses 2 flagellar proteins |
| Answer A Explanation | AnswerAExp::S. enterica has 2 flagellar variants. |
| Answer B | AnswerB::Intragenic recombination causes pilus antigenic variation in S. enterica |
| Answer B Explanation | AnswerBExp::Neisseria gonorrhea undergoes intragenic recombination causes pilus antigenic variation. |
| Answer C | AnswerC::Antigenic drifts and shifts allow continuous antigenic variations in S. enteric |
| Answer C Explanation | AnswerCExp::Influenza virus undergoes antigenic drifts and shifts. |
| Answer D | AnswerD::S. enterica undergoes programmed rearrangement |
| Answer D Explanation | AnswerDExp::Parasites, such as trypanosomes undergo programmed rearrangement. |
| Answer E | AnswerE::S. enterica undergoes recombination between extragenic repetitive elements on linear plasmids |
| Answer E Explanation | AnswerEExp::Borrelia hermsii undergoes recombination between extragenic repetitive elements on linear plasmids to cause relapsing fevers. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::Several infectious agents, whether bacteria, parasites, or virus, undergo different processes to achieve antigenic variation. Salmonella is a classic examples of antigenic variation by formation of 2 flagellar variants; where filament proteins FLjB and FliC are alternatively expressed. This process is in fact mediated by DNA inversion event at the level of the chromosome. This is in contrast to other organisms and viruses that achieve antigenic variation by different ways, such as pilus protein recombination in Neisseria, or antigenic drifts and shifts in influenza viruses.
Educational Objective: Salmonella has 2 flagellar variants that are alternatively expressed to allow antigenic variation. Reference: Bonifield HR, Hughes KT. Flagellar phase variation in salmonella enterica is mediated by a posttranslational control mechanism. J Bacteriol. 2003;185(12):3567-3574. Dai Q, Restrepo BI, Porcella SF, et al. Antigenic variation by Borrelia hermsii occurs through recombination between extragenic repetitive elements on linear plasmids. Mol Microbiol. 2006;60(6):1329-43. |
| Approved | Approved::No |
| Keyword | WBRKeyword::antigen, WBRKeyword::antigenic, WBRKeyword::variation, WBRKeyword::salmonella, WBRKeyword::enterica, WBRKeyword::flagellar, WBRKeyword::variants, WBRKeyword::flagella, WBRKeyword::protein, WBRKeyword::expressed, WBRKeyword::expression |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |