CTLA-4 is a co-stimulatory receptor on T cells that belongs to the same family as the CD28 co-stimulatory receptor. However, CTLA-4 is antagonistic to CD28. Which of the following could be a functional advantage of CTLA-4 expression within the immune response?
A. CTLA-4 competes with CD28 for ligand binding so that, if CD28 binds to its ligand, the response will be magnified.
B. CTLA-4 is often given to immunosuppressed individuals to trigger an immune response.
C. CTLA-4 limits the immune response of TC and TH cells after an infection has been cleared.
D. CTLA-4 limits TC activity in healthy individuals during a viral infection.
E. CTLA-4 reduces the lag time between antigen presentation to a TH cell and B cell activation.
Answer: C
Biology
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- How long ago do scientists believe life first began on Earth?
- What process produces Earth's atmospheric oxygen?
- What evidence points to the date of the appearance of the first oxygen-producing organisms?
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- Animals first appeared during the _____.
- The Cenozoic era began approximately _____ million years ago.
- ____ were the dominant vertebrate life form during the Mesozoic era.
- Most modern animal phyla evolved during the _____ era.
- Bony fish first evolved during the _____ .
- Life arose during the _____.
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- The Mesozoic era began approximately _____ million years ago.
- The Precambrian time began at least _____ million years ago.
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- Reptiles first appeared during the _____ era.
- We are living during the _____era.
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- _____ were the dominant vertebrate life form during the Paleozoic era.
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