THE IMMUNE SYSTEM
I.
II.
III.
IV.
The Immune System
A.
Overview
1.
Defense against small “invaders”
2.
examples: viruses, bacteria, protists, fungi
3.
effects
a.
“steal” cell components
b.
insert their own DNA (or RNA)
c.
disrupt cell integrity
d.
toxic excretions
4.
immune system: array of tissues and cells along w/ certain organs whose
primary function is to protect the body from invading organisms & the harmful
substances some of the produce
a.
pertains to humans & a few other mammals
First line of defense
A.
“Barrier” defense
1.
integument (skin & mucous membranes)
a.
is tough and “poisonous”
1)
toughness from keratin, a protein resistant to most bacterial
enzymes
2)
poison from sweat & oil glands, which are toxic to bacteria
2.
Defense of body passages
a.
mucous secretions trap invaders
b.
strong stomach acid kills anything swallowed
c.
lysozymes—antibacterial enzymes in tears and other secretions
d.
“friendly” bacteria (i.e., E. coli) use up available nutrients, starving competitors
Secondary defenses
A.
Types of defenses
1.
Nonspecific
a.
chemical & molecular agents, certain WBC’s (white blood cells)
b.
response is direct and immediate
2.
Specific
a.
also involves chemical agents & cells
b.
complex; requires time for preparation (and previous exposure)
Nonspecific chemical defenses (4 major kinds; invaded or injured cells release chemicals to
destroy/hinder invader
A.
Histamine
1.
brings redness & swelling associated w/ inflammation & infection
2.
spreads the release of defenseive cells & chemicals @ troubled site (includes clotting
agents)
3.
results in:
a.
vasodilation—increased blood flow
b.
increases permeability of capillaries, permitting rapid escape of defensive
agents
4.
antihistamines—reduces these actions
B.
Kinins—polypeptides that increase circulation and capillary permeability, adding to the
inflammatory response
1.
attract phagocytic cells
2.
causes pain in nerve endings to encourage the favoring of an injured area to permit
healing
C.
Complement
1.
V.
VI.
battery of 20 plasma proteins that act directly by attacking invaders & indirectly by
cooperating w/ other agents of the immune system
a.
direct action—proteins work sequentially
1)
each step amplifies previous ones (called a cascade)
2)
complement coats surface of invader
--makes invader susceptible to phagocytes
--opsonization: phagocytes have specific complement recognition
sites (cb3 receptors) to which phagocytes attach to bound complement/invader complex
--complement may also disrupt invader cell membrane
D.
Interferon (3 types)
1.
stimulates cells of body to resist attack of viruses
2.
blocks protein synthesis of viral coat
3.
stimulates inflammatory & immune response
4.
is a potential treatment of certain cancers (works in a rare form of leukemia)
Nonspecific cellular defenses (the leukocytes)
A.
General
1.
WBCs produced in red bone marrow by stem cells (continually)
2.
3 of 5 kinds are phagocytes (engulf & ingest)
a.
eosinophils
b.
neutrophils
c.
monocytes
3.
basophils—impt. In inflammatory response
4.
lymphocytes—a specific cellular defense (but also involved in nonspecific)
B.
The phagocytes
1.
commonly associated w/ connective tissue in the linings of liver, kidney, lung, capillaries,
spleen, and lymph nodes
a.
some are in brain and blood
2.
drawn to site of infection by chemicals (kinins, complement)) or sometimes by bacterial
chemicals
3.
“go to work” within an hour of infection
a.
pus=remains of phagocytes that perish
4.
phagocytic specificity
a.
eosinophils: only weakly phagocytic
--attack & kill parasitic worms/larvae
--release toxic granules
b.
neutrophils
--1st to congregate
--massive #’s (~100 billion produced per day)
c.
monocytes—have a large lobed nucleus
--grow into macrophages at site of infection
--are prodigious
C.
Natural Killer (NK) cells
1.
are a lymphocyte
2.
plays an exclusively nonspecific role
3.
little are known about their development
4.
attack only the body’s own diseased cells
5.
are key to the development/spread of cancer if they don’t do their jobs
Specific cellular & chemical defense
A.
“The immune response”
1.
requires exposure to invading agent
2.
slow to start
3.
gives long-lasting protection
VII.
4.
encouraged by vaccinations
5.
the reason you usually don’t get the same infection twice (with obvious exceptions)
B.
Lymphoid tissues/lymphocytes
1.
lymphocytes= white blood cells that arise in red bone marrow early in fetal
development
2.
congregate in primary & secondary lymphoid tissue
a.
primary=thymus, red bone marrow
b.
secondary=lymph nodes, tonsils, adenoids, spleen & Peyer’s patches in small
intestine
3.
develops in primary tissues (matures)
4.
actual defense occurs in secondary tissues
C.
B and T lymphocytes
1.
T-cells differentiate in thymus
2.
B-cells differentiate in red bone marrow or liver
3.
The cells can only be distinguished chemically by their surface proteins
D.
Humoral & cell-mediated response
1.
B-cells: make & secrete antibodies & act as memory cells
a.
humoral response=secretion of antibodies
2.
T-cells: cell-mediated response
a.
attach body’s diseased cells (cancerous, infected, etc.)--Tc
b.
some activate B-cells—Th
c.
some are for memory— Tm
Antibodies & humoral response
A.
Antibody (immunoglobulin)
1.
special proteins secreted by B-cells in response to the presence of a “nonself”substance
2.
antigen=foreign (nonself) substance that triggers immune responses (also called an
“immunogen”)
a.
may be proteins, amino acids, nucleic acids, etc.
b.
contain special sites (antigenic determinant) for Ab to recognize
B.
Ab/Ag interactions
1.
Ab binds to Ag (several), causing clumps for phagocytes to devour
2.
complement will be activated
3.
opsonization occurs if complement is activated
**create a flow chart of immune response; use if-then statements**