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The Immune System:
Why we all don’t look like this
I. Sources of Immunity
A. Inherited or
Acquired
1.Inherited (aka innate or
inborn)- from
development in the
womb
2.Acquired- after birth,
from body's exposure to
an antigen (NATURAL)
or immunization
(ARTIFICIAL)
(Types of Acquired Immunities)
a. Active- own body's response to antigen by making
antibody, longer-lasting
ex. Measles (nat.), Polio vacc. (artif.)
b. Passive- body is given the antibodies directly, temporary
but immediate
ex. Breast feeding (nat)
vs
II. Nonspecific defense mechanisms: general, innate
barriers to infection
A. Mechanical and Chemical Barriers- 1st line
1. Skin and mucosa
2. Secretions like sebum, mucus, enzymes
Genetically Modified Skin that is
resistant to infection
B. Inflammation- 2nd line
1.Mediators released after tissue damage
histamine, kinins, prostaglandins
2. Redness, heat, swelling, pain, vasodilation,
fever (mild fever good)
3. Chemotaxis- mediators attract more WBC
C. Phagocytosis- part of 2nd line- ingestion of
microorganisms; pseudopods surround and
lysosomes digest
Trypanosoma : human parasite that
causes African sleeping sickness,
transmitted by tsetse flies
C.
1. Neutrophil- granular WBC, most numerous,
form pus when die
2. Macrophage- aka monocyte, agranular
wbc, names differ based on location
D. Natural Killer Cells- part of 2nd line
1. Police blood and lymph
2. Lymphocytes lyse tumor cells or viruses
E. Interferon- part of 2nd line
1. Protein that interferes with reproduction of viruses
and cancer
2. 3 kinds: leukocyte a, fibroblast b, immune g
3. Genetic engineering
IFN -2a is indicated for hairy
cell leukemia (HCL), acquired
immune deficiency syndrome
(AIDS)-related Kaposi's
sarcoma (KS), chronic-phase
Philadelphia (Ph)
chromosome-positive chronic
myelogenous leukemia (CML)
and chronic hepatitis C (CHC).
F. Complements- 2nd line
1. 20 inactive plasms proteins or enzymes that are
triggered by pathogens
2. cause lysis by binding to pathogen's surface
Increased complement in:
•Cancer
•Certain infections
•Ulcerative colitis
Decreased complement in:
•Cirrhosis
•Glomerulonephritis
•Hereditary angioedema
•Hepatitis
•Kidney transplant rejection
•Malnutrition
• Tissue macrophages (pink/purple), T
lymphocytes (green), and human red
blood cells from a leg wound.
• A tissue macrophage (pink) is a
mature phagocyte that can ingest
and destroy invading microbes,
foreign particles and cellular debris.
• A monocyte (purple)is a circulating
phagocyte that ingests microbes,
invading particles, and cellular debris.
• Lymphocytes are involved in the
specific immune response
– Precursor T cells (T lymphocytes)
• Migrating to the thymus where they
develop into specialized cells (helper T
and killer T cells) that are able to identify
antigens and infected tissue cells
– Precursor B cells (B lymphocytes)
III. Specific Mechanisms- fight specific invaders; 3rd line
Lymphocytes- develop in red blood marrow, fetal liver,
lymph nodes, thymus, and spleen
B. Antigens aka immunogens- foreign invaders or
cancer cells
epitope identifies antigen
Epitope is what the antibody
recognizes
C. Antibodies aka immunoglobulins (Ig)•protein made by B cells
•contains variable or binding site to join with epitope of antigen
1. Structure
a. Y-shaped
b. contains 4 polypeptide chains: 2 heavy & 2 light
c. variable region differs
d. 5 classes: IgM, IgA, IgD, IgE, IgG
2. Functions of antibodies
a. forms antigen-antibody complex
b. inactivates antigens
c. allows macrophages to destroy the complex
d. changes shape so complement can lysis
e. initiates release of mediators
IV. 2 Types of Specific Immunity
A. Cell-mediated Immunity (T cells)
1. Have surface receptors that match antigen's epitope
2. When activate, secrete lymphokines or cytokines to promote
phagocytosis or release lymphotoxins.
3. Killer T cells- release lymphotoxin; kill cells taken over by virus or
cancer
4. Helper T cells- help B cells activate into plasma cells to make
antibodies
5. Suppressor T cells- stop T (and B) cells from activating
B. Antibody-mediated immunity, aka humoral
1. Inactivated B cells become activated when in contact
with epitope of antigen
2. B cells can generate 2000 antibodies/ sec
3. Memory B cells remain and become activated later
Types of Immunity
Cell-Mediated
Humoral (antibody)
Major cell type
involved
T-cells
B-cells
How cell is activated Self cells or antigen Antigen contacts Bpresenting cells
cell
(Helper T-cell can
co-activate)
Response
T-cells produce
B-cells produce
cyto-toxic T-cells
plasma cells that
that attack antigen produce antibodies
presenting cells or
helper T-cells that
get B-cells involved
Memory cells
(long-lasting
immunity)
Memory T-cells
T-lymphocytes
Memory B-cells
V. Organ Transplants and Rejections
A. Common since 1970s
B. Must check ABO groups
C. Post-operation treatment w/ immunosuppressive therapy
D. 4 kinds
1.autograph- same person
2.isograph- identical twins
3.allograph- same species
4.xenograph- different species