:2How Lymphocytes Produce Antibody
The scanning electron micrograph (right) shows a human macrophage
(gray) approaching a chain of Streptococcus pyogenes
Riding atop the macrophage is a spherical lymphocyte. Both macrophages and lymphocytes
can be found near an infection, and the interaction between these cells
is important in eliminating infection.
Below is an animation that illustrates
the basic cell-cell interactions that lead to antibody production can
be seen in the accompanying animation. Antigen Processing
When the macrophage eats bacteria, proteins (antigens)
from the bacteria are broken down into short peptide chains and those
peptides are then
"displayed" on the macrophage surface attached
to special molecules called MHC II (for Major Histocompatibility Complex
Bacterial peptides are similarly processed and displayed
on MHC II molecules on the surface of B lymphocytes.
Helper T Cell Stimulating B Cell
When a T lymphocyte "sees" the
same peptide on the macrophage and on the B cell, the T cell stimulates
the B cell to turn on antibody production. Antibody Production
The stimulated B cell undergoes repeated cell
divisions, enlargement and differentiation to form a clone of antibody
secreting plasma cells.
Hence. through specific antigen recognition
of the invader, clonal expansion and B cell differentiation you acquire
an effective number of plasma cells all secreting the same needed antibody.
That antibody then binds to the bacteria making them easier to ingest
by white cells. Antibody combined with a plasma component called "complement" may
also kill the bacteria directly.