Download The Immune System Body Defenses Innate Defenses Surface

The Immune System
Body Defenses
· 2 intrinsic systems
1. innate (nonspecific) defenses
Ch. 21
The Immune System
Ch. 21
Innate Defenses
· prevent the approach, deny the entrance, or limit
the spread of pathogens
harmful or disease-causing microorganisms
· present at birth
· rapid response (same every time)
does not discriminate between
one threat or another
first line of defense - skin and
mucous membranes
second line of defense phagocytes, NK cells,
inflammation, antimicrobial
proteins, fever
2. adaptive (specific) defense
protect against specific threats
third line of defense - B and T cells
Surface Barriers
· skin, mucous membranes and their secretions
· keratin resistant to microorganisms, weak acids/bases,
bacterial enzymes, and toxins
nicks and cuts allow organisms to invade
· mucous membrane secretions
acidic secretions - sweat, sebum, vaginal secretions,
tears
HCl - stomach
saliva - contains lysozyme
mucus - respiratory and
digestive systems
Internal Defenses
· phagocytes - move between cells and recognize
chemical antigens that stimulate phagocytosis
carried out by macrophages (type of monocyte) and
neutrophils
· natural killer (NK) cells - lymphocytes that "polices" the
body looking for cells lacking "self" antigens
induce apoptosis (programmed cell death) and
release chemicals that enhance inflammation (cytokines)
· inflammation - triggered by physical trauma, intense
heat, irritating chemicals, or infection by viruses,
fungi, or bacteria
4 cardinal signs - redness, heat, swelling, pain
prevents the spread of damaging agents to nearby
tissues
disposes of cellular debris and pathogens
prevents movement to encourage healing/repair
Internal Defenses
· antimicrobial proteins
interferons - proteins released from virus-infected
cells that trigger the production of antiviral proteins
that interfere with viral replication inside healthy
cells; mobilize the immune system
complement - lyses microorganisms, enhances
phagocytosis, intensifies inflammatory and immune
responses
· fever - abnormally high temperature
initiated by pyrogens (chemicals released by
leukocytes and macrophages)
high body temp inhibits microbial multiplication (iron
and zinc stored in liver) and enhances body repair
processes
The Immune System
1 All of the following are innate defenses
EXCEPT
A complement proteins
B
inflammation
C
mucous membrane secretions
D
antibodies
E
NK cells
3 Innate defenses, like fever and
interferons, are nonspecific and
acquired throughout our lifetime.
True
False
2 MATA: Which innate defenses involve
an increase in temperature?
A
complement
B
fever
C
inflammation
D
interferons
Adaptive Defenses
· characteristics
specificity - recognizes and reacts to specific antigens
versatility - not restricted to the first infection
memory - mounts stronger attacks on "remembered"
antigens
tolerance - can ignore "self" antigens
· types
cell-mediated immunity (T cells) - cells killing cells
antibody-mediated (humoral) immunity (B cells) antibodies mark pathogens for destruction
Cell-Mediated Immunity
· T cells cannot recognize antigens in their natural state;
can only recognize processed or internalized antigens
· target cells infected by viruses and bacteria, abnormal
or cancerous cells, and cells of transplanted foreign
tissue
· activated T cells release cytokines (chemical
messengers), like interferon or interleukins, that amplify
and regulate immune responses
· T cell differentiation
helper T (TH) - "director" of adaptive immune response
activate B cells, T cells, and macrophages, recruit other
immune cells to join the fight
AIDS destroys helper T cells (no immune response)
cytotoxic T (TC) - attack and kill other cells
regulatory R (TREG) - suppress response of B and T cells
The Immune System
Cell-Mediated Immunity
Antibody-Mediated Immunity
Antibody-Mediated Immunity
· starts with antigen challenge
first encounter between an immunocompetent B cell and its
antigen; activates B cell
immunocompetence - ability to recognize a specific antigen
· activated B cells divide and produce plasma cells
· plasma cells secrete antibodies
2000/sec for 4 or 5 days
· antibodies bind with their specific antigen, marking it for
destruction
form antigen-antibody complexes
PLAN: precipitation (falling out of solution), lysis
(complement activation), agglutination (clumping),
neutralization (blocks toxic effect)
· B cells that do not become plasma cells turn into memory
B cells
MHC = Major Histocompatability Complex
4 __ cells are responsible for cellmediated immunity, while __ cells are
responsible for humoral immunity.
A
T, B
B
B, T
C
helper T, cytotoxic T
D
cytotoxic T, helper T
memory B cells allows the body to mount an immediate
attack when they encounter the same antigen a second
time
Primary vs. Secondary Response
· primary response - first exposure to a particular antigen
6-7 day lag time after antigen challenge
allows B cells for that antigen to replicate and start
producing antibodies
peak levels around 10 days
· secondary response - subsequent exposure(s) to the
same antigen
Antibody Structure
· heavy chains - identical to each
other; more than 400 amino acids
· light chains - identical to each
other; half as long as heavy chains
· variable region - depends on the antigen
· constant region - same for all antibodies
· antigen-binding site - variable regions of
heavy and light chains; antigen specific
memory cells recognize
the antigen
response is faster, longer,
and more effective
MADGE Antibodies
· antibody = immunoglobulin (Ig)
· IgM - first antibody released
· IgA - found in secretions
(i.e. mucus, sweat, etc.)
· IgD - found on B cell surfaces
· IgG - most abundant antibody;
can cross placenta
· IgE - involved in inflammation
and allergic reactions
The Immune System
5 Immunoglobulins are antigen-specific
and are made during the primary
response.
active immunity can be naturally acquired (getting
sick) or artificially acquired (vaccines)
passive immunity is produced by the natural transfer
of antibodies (mom's placenta or milk) or artificial
transfer of antibodies (donated antibodies that
jumpstart your own attack; hepatitis, snake bites,
rabies, tetanus)
True
False
6
Types of Immunity
· specific immunity may involve innate immunity
(genetically determined, present at birth) or
acquired immunity (developed during life)
· 2 types of acquired immunity
MATA: When I was sick, I spread my
germs every time I coughed. What
type(s) of immunity was I helping you
develop by sharing my germs?
(You're welcome by the way :-))
A
acquired
B
innate
C
specific
D
active
E
passive
Immune Disorders
· immunodeficiencies - immune system does not
develop normally or the immune response is blocked
SCID - severe combined immunodeficiency
syndromes; very few B and T cells
AIDS - acquired immune deficiency syndrome; results
from HIV infection; attacks CD4 proteins/helper T
cells
· autoimmune diseases - immune response mistakenly
targets normal body cells and tissues
multiple sclerosis (MS), Graves' disease, Type 1
diabetes mellitus, lupus, rheumatoid arthritis
· hypersensitivities - excessive reactions to harmless
threats (allergens)