Immunology USMLE Step 1 Practice Question
A 28-year-old researcher conducts an in vitro study exposing naive CD4+ T cells to peptide-bound MHC-II molecules presented by antigen-presenting cells deliberately engineered to lack B7 expression. Flow cytometry reveals normal TCR engagement and calcium influx. However, the T cells survive without proliferating and fail to mount immune responses upon subsequent antigen re-exposure. Notably, IL-2 production remains absent. Which mechanism best explains this anergic state?
Answer choices
- AAnergy due to lack of costimulatory signalCorrect answer
- BMembrane attack complex mediated cell lysis
- CClonal expansion driven by IL 5
- DDeletion of self reactive clones in the thymic medulla
- EClass switching due to CD40 signaling
- FActivation-induced cell death due to repeated Fas-FasL interactions
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