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Humoral Immunity (Antibodies)
 Initiation of the humoral immune
response can occur when a pathogen is recognized by receptors
on B cells. Antigen-derived peptides
are then displayed on the B cell surface bound to class II molecules.
- CD4+ T cells, also called T helper (Th) cells, have their
own receptors that recognize the peptide bound to the B cell
class
II molecule.
- When the CD4+ T cell recognizes the antigen, it becomes activated
and releases stimulatory molecules called Type II cytokines.
- Type II cytokines, in turn, activate the B cell to produce
and secrete antibodies, which can protect against infection by
the
same pathogen in the future. Some B cells become “memory” cells
that remain in the body for years.
However, for clearance of established infection, cellular immunity
is usually required. One of the most important participants in
cellular immunity are T cells. There are different types of T cells.
Some T cells can assist antibody production while others can directly
attack infected or diseased cells. This “killer” function,
which resides within some types of T cells (and in other cell types
which make up cellular immunity) is thought to be important for
clearance of established infection or eradication of cancerous
cells.
Next: Cellular Immunity
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