Question

Effector T cells are activated when their antigen-specific receptors and either the CD4 or the CD8 co-receptors bind to peptide: MHC complexes. Ligation of the T cell receptor and co-receptor does not, on its own, stimulate naive T cells to proliferate and differentiate into armed effector T lymphocytes. A second or co-stimulatory signal from an antigen-presenting cell is required. These molecules are members of the B7 family of ligands. On naïve T cells, CD28 is the only receptor for B7 molecules. Once T cells are activated, they express an additional receptor called?

MAGE
Ras
CTLA-4
IL-4
IL-5

Answer 1

Once naïve T cells are activated, they express an additional receptor called (3) CTLA-4, which interacts with B7 family ligands to help regulate the immune response.

Step-by-step explanation:

Once naïve T cells are activated by recognition of a pathogen's antigen through the T cell receptor (TCR), they require a second co-stimulatory signal from an antigen-presenting cell (APC). This involves the binding of the B7 family of ligands on the APC to the CD28 receptor on the naïve T cell.

After activation, T cells express an additional receptor for B7 molecules, which is CTLA-4. While CD28 is constitutively expressed on naïve T cells and has an activating role, CTLA-4 is induced only after T cell activation and helps to regulate and dampen the immune response.