Question:medium
Which of the following is the most potent activator of T cells?
Which of the following is the most potent activator of T cells?
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Think of the professional APC that uniquely primes naive T cells with both peptide-MHC and B7 co-stimulation.
Updated On: Jun 24, 2026
- B cells
- Follicular dendritic cells
- Mature dendritic cells
- Macrophages
Show Solution
The Correct Option is C
Solution and Explanation
Naive T lymphocytes can only be switched on when an antigen-presenting cell delivers two simultaneous messages: a peptide loaded onto an MHC molecule and a co-stimulatory handshake through the B7-CD28 axis. Among all body cells capable of presenting antigen, the dendritic cell stands out as the only true professional that can prime a resting T cell that has never seen its antigen before. Once a dendritic cell matures, it greatly upregulates surface MHC II along with $CD80$ and $CD86$, giving it an unmatched capacity to engage and stimulate T cells in the lymph node paracortex. B cells and macrophages do present antigen, but they mainly amplify responses that are already underway and carry fewer co-stimulatory molecules, while follicular dendritic cells serve B-cell selection rather than direct T-cell priming. Therefore the cell that most powerfully turns on T cells is the mature dendritic cell. \[\boxed{\text{Mature dendritic cells}}\]
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