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
Both (a) and (b)
By rearrangements of the DNA encoding the variable regions of the heavy and light chains
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 derived from bone marrow stem cells
can be attracted to the site of an infection following activation of complement
All of these
are a type of phagocyte that can engulf and kill bacteria

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Immune System
The role of the M cell is to

pass bacteria or virus to underlying macrophages for processing and presentation of antigen
induce apoptosis in virus-infected small intestinal epithelia cells
trap virus in mucus and prevent entry
they use their cilia to propel mucus out of the small intestine

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