The Immune Response An immune response to foreign antigen requires
the presence of an antigen-presenting cell (APC), (usually either a
macrophage or dendritic cell) in combination with a B cell or T
cell. When an APC presents an antigen on its cell surface to a B
cell, the B cell is signalled to proliferate and produce antibodies
that specifically bind to that antigen. If the antibodies bind to
antigens on bacteria or parasites it acts as a signal for pmns or
macrophages to engulf (phagocytose) and kill them. Another important
function of antibodies is to initiate the "complement destruction
cascade." When antibodies bind to cells or bacteria, serum proteins
called complement bind to the immobilized antibodies and destroy the
bacteria by creating holes in them. Antibodies can also signal
natural killer cells and macrophages to kill viral or bacterial-
infected cells.

The Organs of the Immune System

Bone Marrow -- All the cells of the immune system are initially
derived from the bone marrow. They form through a process called
hematopoiesis. During hematopoiesis, bone marrow-derived stem cells
differentiate into either mature cells of the immune system or into
precursors of cells that migrate out of the bone marrow to continue
their maturation elsewhere. The bone marrow produces B cells,
natural killer cells, granulocytes and immature thymocytes, in
addition to red blood cells and platelets.

Thymus -- The function of the thymus is to produce mature T cells.

Lymph Nodes -- The lymph nodes function as an immunologic filter for
the bodily fluid known as lymph. The Cells of the Immune System

T-Cells -- The main function of the T helper cell is to augment or
potentiate immune responses by the secretion of specialized factors
that activate other white blood cells to fight off infection.

Natural Killer Cells -- They function as effector cells that
directly kill certain tumors such as melanomas, lymphomas and viral-
infected cells, most notably herpes and cytomegalovirus-infected
cells.

B Cells -- The major function of B lymphocytes is the production of
antibodies in response to foreign proteins of bacteria, viruses, and
tumor cells. Antibodies are specialized proteins that specifically
recognize and bind to one particular protein that specifically
recognize and bind to one particular protein.

Granulocytes or Polymorphonuclear (PMN) Leukocytes -- These cells
are predominantly important in the removal of bacteria and parasites
from the body.

Macrophages -- They are often referred to as scavengers or antigen-
presenting cells (APC) because they pick up and ingest foreign
materials and present these antigens to other cells of the immune
system such as T cells and B cells.

Dendritic Cells -- Dendritic cells, which also originate in the bone
marrow, function as antigen presenting cells (APC).


Next week, we'll discuss supplements that will boost our immune
system. I particularly like Cat's Claw and pau D' Arco.