Transcript THE IMMUNE SYSTEM

THE IMMUNE SYSTEM
•
The Perfect World
•
The Real World
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ANTIBODIES
STRUCTURE
CLASS
Distribution of immunoglobulins
• IgG & IgM predominate in
plasma while IgG &IgA are the
major isotypes in extracellular
fluid within the body
• IgA predominates in secretions
across epithelial including breast
milk. The fetus received IgG from
the mother by transplacental
transport. IgE is found mainly
with mast cells (specially of
respiratory tract, GIT & skin)
• The brain is normally devoid of
immunoglobulins
The basic structure of immunoglobulin
Variable domain
Heavy chain
Light chain
V
VH
D
V
J
J
VL
CH1
Fab
CL
Hinge region
Constant domain
CH2
CH3
CH4 (some antibody classes only)
Fc
Antibody can be secreted from plasma
cells or expressed on the cell surface of B
lymphocytes. in both forms, they
recognize and bind foreign antigens
Viral infection of cells can be blocked by
neutralizing antibodies
Neutralizing antibodies they represent antibodies that
bind to the receptor binding site on the toxin molecule &
prevent the toxin from binding to the target cell & thus
protect the cell from attack
Ag-Ab interaction leads to cell
lysis
Leads to
Antigen antibody interaction facilitates
Ag-Ab interaction
enhance phagocytosis
phagocytosis
Video film (2)
Tissues of the immune System
Primary (Central) Lymphoid Organs
Bone Marrow
Thymus
Where B & T cells become competent
to Respond to Ag
Secondary lymphoid organs
Spleen
Lymph nodes
Where Adaptive IR is Initiated
MALT
- Tonsils
- Peyer’s
patches
- Appendix
- Bronchial
& mammary
tissue
Immunity is the result of the action of two types lymphocytes,
the B lymphocytes and the T lymphocytes.
B cells produce antibodies that are secreted into the blood and
lymph.
T cells attack the cells that have antigens that they recognize.
 Killer T Cells (lymphocytes) recognize surface
markers on other cells labeled for destruction. They,
Killer T Cells, help to keep virus-infected or malignant
cells in check.
 Here, a smaller Killer T Cell (arrow) is attacking and
killing a much larger flu virus-infected target. The
sequence represents 30 minutes elapsed time.
• Once a white cell has left the blood vessel and
migrated to the enemy, the next job is to EAT the
microbe.
• The macrophage is a large phagocyte. A
phagocyte is an eating cell (phago = "eating",
cyte = "cell") which engulfs invaders.
The scanning electron micrograph above, shows a human
macrophage (gray) approaching a chain of Streptococcus
pyogenes (yellow). 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.
Figure 16.6