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

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

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Immune System
Polymorphonuclear leukocytes (or PMNs)

are a type of phagocyte that can engulf and kill bacteria
All of these
can be attracted to the site of an infection following activation of complement
are derived from bone marrow stem cells

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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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