Download The Immune System

The Immune System
2 Divisions of Immunity in Humans and
Other Mammals
I. Innate Immunity
“Non-Specific”
II. Acquired immunity
“Specific”
A. Barrier Defenses
Skin
B. Cellular Defenses
Microbes/antigens
PHAGOCYTIC CELL
Vacuole
Lysosome
containing
enzymes
There are different types of
phagocytic cells:
Fig. 43-7
Interstitial fluid
Adenoid
Adenoid
Tonsil
Tonsil
Blood
Blood
capillary
capillary
Lymph
Lymph
nodes
nodes
Spleen
Spleen
Peyer’s patches
Peyer’s
patches
(small
intestine)
(small intestine)
Appendix
Appendix
Lymphatic
vessels
Tissue
Tissue
cells
cells
Lymph
Lymph
node
node
Lymphatic
Lymphatic
vessel
vessel
Masses of
Masses of
defensive
cells
defensive cells
Fig. 43-8-3
D. Inflammatory Responses
Pathogen
Splinter
Chemical Macrophage
signals
Mast cell
Capillary
Red blood cells Phagocytic cell
Fluid
Phagocytosis
II. Acquired immunity
lymphocyte receptors provide
pathogen-specific recognition
Fig. 43-9
B cells and T cells have receptor proteins
that can recognize and bind to antigens
Antigenbinding
site
Antigenbinding site
Antigenbinding
site
Plasma
membrane
B cell
(a) B cell receptor
Cytoplasm of B cell
Cytoplasm of T cell
(b) T cell receptor
T cell
B Cells
Antigen-specific
B cell receptor
Class II MHC and
processed antigen
are displayed
Antigen
Antibodies
(Immunoglobins)
B cell
Cytokines (Lymphokines) Plasma cell
bacteria
Activated
helper T cell
T Cells
Resting helper T cell
Resting cytotoxic T cell
Cytokines
Released by
Helper T-Cells
Granule w/
destructive
enzymes
Activated helper T cell
Activated when they encounter
infected cells that are
presenting antigens
Activated killer cell
Killer Cells: Cytotoxic Ts
Killer cell
Surface contact
Target cell
Target-oriented
granules
Fig. 43-12
Infected cell
Microbe
Antigenpresenting
cell
1 Antigen
associates
with MHC
molecule
Antigen
fragment
Antigen
fragment
1
1
Class I MHC
molecule
T cell
receptor
(a)
2
2
Cytotoxic T cell
Class II MHC
molecule
T cell
receptor
2 T cell
recognizes
combination
(b)
Helper T cell
Activation of B Cells to Make Antibody
Circulating antibody
Antigen
Antigen-specific
B cell receptor
Antigen
Class II MHC
B cell
Antigenpresenting cell
Antigen is
processed
Class II MHC Antigen-presenting cell
and
processed
antigen are
displayed
Cytokines
Activated
helper T cell
Antibodies
Plasma cell
Fig. 43-14
Animation: Role of B Cells
Antigen molecules
B cells that
differ in
antigen
specificity
Antigen
receptor
Antibody
molecules
Clone of memory B cells
Clone of plasma cells
Fig. 43-16
Humoral (antibody-mediated) immune response
Cell-mediated immune response
Key
Antigen (1st exposure)
+
Engulfed by
Gives rise to
Antigenpresenting cell
+
Stimulates
+
+
B cell
Helper T cell
+
Cytotoxic T cell
+
Memory
Helper T cells
+
+
+
Antigen (2nd exposure)
Plasma cells
Memory B cells
+
Memory
Cytotoxic T cells
Active
Cytotoxic T cells
Secreted
antibodies
Defend against extracellular pathogens by binding to antigens,
thereby neutralizing pathogens or making them better targets
for phagocytes and complement proteins.
Defend against intracellular pathogens
and cancer by binding to and lysing the
infected cells or cancer cells.
Fig. 43-17
Helper T Cells
Antigenpresenting
cell
Peptide antigen
Bacterium
Class II MHC molecule
CD4
TCR (T cell receptor)
Helper T cell
Humoral
immunity
(secretion of
antibodies by
plasma cells)
Cytokines
+
B cell
+
+
+
Cytotoxic T cell
Cell-mediated
immunity
(attack on
infected cells)
Fig. 43-18-3
Released cytotoxic T cell
Cytotoxic T cell
Perforin
Granzymes
CD8
TCR
Class I MHC
molecule
Target
cell
Dying target cell
Pore
Peptide
antigen
Fig. 43-19
Antigen-presenting cell
Bacterium
Peptide
antigen
Class II MHC
molecule
TCR
CD4
B cell
+
Cytokines
Clone of plasma cells
Secreted
antibody
molecules
Endoplasmic
reticulum of
plasma cell
Helper T cell
Activated
helper T cell
Clone of memory
B cells
2 µm
Fig. 43-21
Viral neutralization
Opsonization
Activation of complement system and pore formation
Bacterium
Complement proteins
Virus
Formation of
membrane
attack complex
Flow of water
and ions
Macrophage
Pore
Foreign
cell