Immune System
T cell receptors (or TCR) on CD4+ T cells

recognize peptides associated with MHC class I molecules
recognize peptides associated with MHC class II molecules
recognize peptides not associated with MHC molecules
are secreted out into the environment to bind antigens

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Immune System
Numerous antibodies can be prepared, against one antigen, each binds to unique epitopes. How is this antibody diversity generated?

By the combination of different heavy and light chains that form the antigen binding site
By rearrangements of the DNA encoding the variable regions of the heavy and light chains
Antibody proteins can physically change their shape to bind different epitopes
Both (a) and (b)

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Immune System
Which of the following is correct for CD8 T cells?

In the thymus, CD8 T cells undergo positive selection only, whereas CD4 T cells undergo negative selection only
CD8 T cells only recognize virus-infected cells
CD8 T cell receptor recognizes epitopes that are also commonly recognized by B cells
CD8 T cells can kill individual virus-infected cells in a contact dependent fashion

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