LECTURE 10: IMMUNSE SYSTEM Flashcards
- lymphatic capillaries take up and return excess fluid
to the bloodstream - lacteals receive lipoproteins and transport them to
the bloodstream - helps defend body against disease
Lymphatic System
lymphatic organs:
-red bone marrow,
-thymus gland,
-tonsils,
-spleen,
-lymph vessels (lymphatic capillaries)
-lymph nodes
take up and return excess
fluid to the bloodstream
Lymphatic capillaries
Capsule surrounding two distinct
regions, cortex and medulla
Lymph Nodes
congregate in cortex when
fighting off a pathogen
Lymphocytes
concentrated in medulla -
cleanse lymph
Macrophages
Lymph nodes named for their __________
location
- Located in upper left
region of abdominal cavity
just beneath diaphragm - Cleanses blood
- Found in all vertebrates
- Mechanical filtration of red blood cells to remove
old red blood cells - Active immune response through humoral and cell-mediated pathway
Spleen
- Patches of lymphatic tissue
located around the
pharynx - First to encounter
pathogens that enter via
the nose and mouth
Tonsils
- Located along trachea
behind the sternum in
upper thoracic cavity - Produces thymic hormones
Thymus Gland
- Origin for all types of blood
cells - Area of maturation for most
white blood cells
Red Bone Marrow
- Blind-ended tube connecting to the caecum
- Shrunken remnant of the part of the caecum
- found in the digestive tracts of many extant
herbivores - house mutualistic bacteria which help animals
digest the cellulose molecules that are found
in plants - may harbour and protect bacteria that are
beneficial in the function of the human colon
Appendix
inflammation of the appendix
Appendicitis
2 category of Defense Mechanism
-Innate immunity (Nonspecific defense mechanism)
-Adaptive Immunity (Specific defense Mechanism
Category under Innate immunity (Nonspecific defense mechanism)
-First line of defense
-Second Line of defense
Category under Adaptive Immunity (Specific defense Mechanism
third line of defense
-(non-specific) is present before any exposure to pathogens and is effective from the time of birth.
-It responds to a broad range of pathogen
-Recognition of traits shared by broad ranges of pathogens, using a small set of receptors
- Rapid response
Innate immunity
-(acquired/specific), develops after exposure to agents such as microbes, toxins, or other foreign substances.
-It involves a very specific response to pathogens
-Recognition of traits specific to particular pathogens, using a vast array of receptors
- Slower response
Adaptive immunity
agents that cause disease, infect a wide
range of animals, including humans
Pathogens
recognizes foreign bodies and
responds with the production of immune cells and proteins
immune system
All animals have__________________, a
defense active immediately upon infection
innate immunity (non-specific)
Components of Immune system recognition and response
-immunocytes (lymphocytes and
macrophages)
-plus a diverse array of molecules
(antibodies, lymphokines, etc.)
Formed elements (45 %) – produced by bone marrow
BLOOD
Multipotential stem cell —–>
-Myeloid stem cell
-Lymphoid stem cell
Myeloid stem cell—>
Macrophage Precursor—->Monocyte—> Macrophage
Lymphoid Stem cell —->
-B cell precursor
-natural killer precursor
-T cell precursor
B cell precursor—>
B Cell—-> (two possible result)—> Plasma cell/memory cell
Natural killer precursor—>
natural killer cell—>activated natural killer cell
T cell precursor—>
T cell—> (two possible result)—> helper T cells/ cytotoxic T cell
-innate defenses include barrier defenses, phagocytosis, antimicrobial peptides.
-Main function is to prevent infection
-Barrier defenses - skin and mucous membranes of the respiratory, urinary, and urinary tracts
-Mucus traps and allows for the removal of microbes
-Many body fluids including saliva, mucus, and tears are hostile to many microbes
-The low pH of skin and the digestive system prevents growth of many bacteria
First Line of Defense – Natural Barriers
Components of the 1st Line of Defense
-Saliva, sweat, tears and mucus
-Cilia
-Stomach Acid
- Bathe surfaces and wash away many potential invaders
- Many secretions contain antimicrobial proteins
Saliva, sweat, tears and mucus
❑digests cell walls of bacteria
❑destroys many microbes at eyes and upper resp.
tract
Lysozyme
- Traps particles
- Swallow or expel
Mucus
Line the cells of the trachea
(windpipe) and help sweep
out microbes trapped in
mucus there.
Cilia
Kills many microbes
present in food before
they reach intestines.
Stomach Acid
Second Line of Defense – Three Mechanisms
- Phagocytic and Natural Killer Cells’
- Localized Inflammatory Responses
- Antimicrobial Peptides and Proteins
Phagocytic and Natural Killer Cells
a. Neutrophils
b. Monocytes
c. Eosinophils
d. natural killer cells
- attracted to damaged cells, enter the infected
tissue, engulfing and destroying pathogens
*self-destruct and live only for a few days
*Chemotaxis – migration towards the source of
chemical attractant
Neutrophils
migration towards the source of
chemical attractant
Chemotaxis
- transformed to macrophages once they enter the affected tissue; effective and long-lived
- Macrophages – “big-eaters; engulf microbes in a vacuole – fused with lysosomes – kill the microbe
- Mechanism:
▪ generate toxic forms of O2
▪ digestion of microbial
components (lysosomal enzymes)
Monocytes
“big-eaters; engulf microbes in a
vacuole – fused with lysosomes – kill the microbe
Macrophages
Mechanism of monocytes
▪ generate toxic forms of O2
▪ digestion of microbial
components (lysosomal enzymes)
- against larger parasitic
invaders (blood fluke.
Schistosoma mansoni) - discharge destructive
enzymes targeting the parasite’s
external wall
Eosinophils
-circulate through the body and detect abnormal
cells
-release chemicals leading to cell death, inhibiting the spread of virally infected or cancerous cells
-does not attack microbes but destroy virus-infected or abnormal cells
-do not phagocytose but mount an attack via lysis of infected cell
natural killer cells
-Occurs when there is damage to tissue (physical injury) or by entry of microorganisms
-Four symptoms: redness, pain, swelling and heat
-inflammatory response, such as pain and swelling, is brought about by molecules released upon injury of infection
-Mast cells, a type of connective tissue, release
histamine, which triggers blood vessels to dilate and become more permeable
Localized Inflammatory Responses
Four symptoms of localized inflammatory response
redness, pain, swelling and heat
a type of connective tissue, release
histamine, which triggers blood vessels to dilate and
become more permeable
Mast cells
Localized Inflammatory Response : Activated macrophages and neutrophils release _________, signaling molecules that enhance the immune response
cytokines
Localized Inflammatory Response: Enhanced blood flow to the site helps deliver antimicrobial peptides that result in an accumulation of ____
pus
a fluid rich in white blood cells,
dead pathogens, and cell debris from damaged tissues
pus
damage to tissue by physical injury or entry of
microorganisms triggers a localized
inflammatory response
Second Line of Defense
Example of Second Line of Defense
-Fever
-Septic Shock
- systemic inflammatory response triggered by substances
released by macrophages in response to certain pathogens - response to toxins BUT certain WBCs release molecules called
PYROGENS which set the body’s thermostat at a higher temp.
Fever
set the body’s thermostat at a higher temp
PYROGENS
❑inhibits growth of some microbes
❑May speed up phagocytosis and tissue repair by speeding up body chemical reactions
MODERATE fever
a life-threatening condition caused by an
overwhelming inflammatory response
Septic shock
Peptides and proteins function in innate defense by
attacking pathogens or impeding their
reproduction
Antimicrobial Peptides and Proteins
Antimicrobial Peptides and Proteins
a. Lysozymes
b. Interferon
c. Complement system
antimicrobial enzymes present in
saliva, tears, and mucous secretion
Lysozymes
secreted by virus-infected cells; bind
to receptors of non-infected cells and induce them to produce substances
b. Interferon
proteins which carry out
cascade of steps which causes lysis of invading cells
and helps trigger inflammation
Complement system
Second Line of Defense: some microbes have evolved mechanisms for
evading phagocytic destruction. Ex: ____
– outer capsules
– Mycobacterium tuberculosis are readily engulfed but are resistant to lysosomal destruction and can even reproduce inside a macrophage
key cells
of the immune system
Lymphocytes
two main types of
lymphocytes:
B lymphocytes (B cells) and T lymphocytes (T
cells
- Adaptive (specific) immunity
- Bursa of Fabricius – Chang & Glick
- a foreign molecule that elicits a specific response
by lymphocytes is called an antigen - Antigens react to specific antibodies that are
either attached to lymphocytes or are secreted
Third Line of Defense (Adaptive Immunity)
response mounted by the immune
response (lymphocytes) against pathogens or antigens
Immune Response
recognizes and directed against
particular antigens of foreign substances
Antigen-specific
immunity is not restricted to initial
infection site
Systemic
recognizes and mount enhanced
attack on previously encountered antigens
Immune response has memory
T or B cells bind to antigens via ______________ specific to part of one molecule of that pathogen
antigen receptors
a foreign molecule that elicits a specific response by lymphocytes is called an __________
antigen
Antigens react to specific ___________ that are
either attached to lymphocytes or are secreted
antibodies
an antibody interacts with a small, accessible portion of the antigen called an ________ or antigenic determinant
epitope
Each B cell antigen receptor is a ___________________ with two identical ____________ and two identical ____________
-Y-shaped molecule
-heavy chains
-light chains
The constant regions of the chains vary little among B cells, whereas the ______________ differ greatly
variable regions
The variable regions provide_______________
antigen specificity
First step in B cell activation
Binding of B cell antigen receptor to an antigen
First step of B cell activation gives rise to cells
that secrete a soluble form of the protein called an ____________________________
antibody or immunoglobulin (Ig)
Each T cell receptor consists of two different polypeptide chains called ______________
alpha and beta
Antibodies have the
same Y shape as B cell
antigen receptors but are
___________, not membrane
bound
secreted
The tips of the chain form a ___________ region; the rest is a __________ region
-variable (V)
-constant (C)
T cell and B cell antigen receptors are functionally _______-
different
Enormous Variety of B and T cells in the body allows the immune system to respond to
millions of ___________, and thus millions of
_______________
-antigens
-potential pathogens
What activate lymphocyte?
binding of a mature lymphocyte to an antigen
although a microorganism encounters a large
repertoire of B cells and T cells, it interacts only
with ____________ bearing receptors specific for
its various antigenic molecules
lymphocytes
In the body there are few lymphocytes with
antigen receptors for any particular _________
epitope
In the ________________, an antigen is exposed to a steady stream of lymphocytes until a match is made
Lymph Node
Once activated, a B or T cell undergoes multiple cell divisions called?
Clonal Selection
Clonal Selection
produce a clone of identical cells
Some cells from the clone become short-lived ___________ that act immediately against the antigen
effector cells
responsible for long-term
protections against diseases
Immunological Memory
Some cells from the clone become long-lived ____________ that can give rise to effector cells if the same antigen is encountered again
memory cells
Effector cells are ____________ that secrete antibodies
plasma cells
The first exposure to a specific antigen represents the
primary immune response
During primary immune response, selected B and T cells give rise to their
________________
effector forms
In the _____________________, memory cells facilitate a faster, more efficient response
secondary immune response
While B cells and T cells are maturing in the
____________ and __________, their antigen
receptors are tested for potential self-reactivity
-bone marrow
-thymus
What is tested (potential self-reactivity) in the antigen of B and T cells?
– capacity to distinguish self from nonself continues to develop as the cells migrate to lymphatic organs
– autoimmune diseases
Why is it needed to check autoimmune disease in the antigen of B and T cells?
Caused when the immune system mistakes its own cells as pathogens and attack them
The defenses provided by B and T lymphocytes can be divided into humoral immune response and the cell-mediated immune response
Adaptive (Specific) Immunity
antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph
Humoral immune response
specialized T cells destroy affected host cells
Cell-mediated immune response
_______ interact with one important group of
native molecules
T cells
collections of cell surface glycoproteins
encoded by a family of genes called the
major histocompatibility complex (MHC)
have class I and class II MHC molecules on their surfaces
Antigen-presenting cells
Two main classes of MHC molecules mark
body cells as self:
*Class I MHC molecules
*Class II MHC molecules
found on almost
all nucleated cells
Class I MHC molecules
restricted to macrophages, B cells, activated T cells, and those inside the thymus
Class II MHC molecules
two main types of T cells, each responds to one
class of MHC molecule
-Cytotoxic T cells (TC)
-Helper T cells (TH)
have antigen receptors that
bind to protein fragments displayed by the body’s class I MHC molecules
Cytotoxic T cells (TC)
have receptors that bind to
peptides displayed by the body’s class II MHC
molecules
Helper T cells (TH)
___________ cells respond by killing the infected cells
Cytotoxic T
_____________ send out chemical signals that incite other cell types to fight the pathogen
Helper T cells
How Class I MHC molecule function?
If the cell contains a replicating virus, class I
MHC molecules expose foreign proteins that
are synthesized in infected or abnormal cells to
cytotoxic T cells
this interaction (MHC molecule exposing foreign proteins) is greatly enhanced by a __________________ which helps keep the cells together while the TC cell is activated
T surface protein CD8
Binding of Antibodies to antigens inactivates antigen by:
-Neutralization
-Agglutination of antigen-bearing particles
-Precipitation of soluble antigens
-complement fixation (activation of complement)
Five Classes of Immunoglobulins
-IgM (Pentamer)
-IgG (monomer)
-IgA (dimer)
-IgD (monomer)
-IgE (monomer)
Blocks viral binding sites; coats bacteria and/or opsonization
Neutralization
Neutralization, Agglutination of antigen-bearing particles, and Precipitation of soluble antigens enhances?
Phagocytosis
Process of Complement System
- A trigger (like an antibody-antigen complex) initiates the complement cascade by activating the first complement protein in the pathway.
- Activated complement proteins sequentially cleave and activate the next protein in the cascade, amplifying the response.
- C3b binds to the pathogen surface, marking it for phagocytosis by immune cells.
- Complement fragments like C3a and C5a stimulate mast cell degranulation, leading to histamine release and increased vascular permeability.
- In the final step of the cascade, the MAC is formed on the pathogen membrane, causing cell disruption
Complement fixation leads to?
Cell Lysis
part of your body’s immune system that cleans up damaged cells, helps your body heal after an injury or an infection and destroys microscopic organisms like bacteria that make you sick
Complement System
- first to be produced after
initial exposure to antigen - promotes neutralization
and cross-linking of
antigens - very effective in
complement system
IgM (pentamer)
- most abundant Ig in blood
- promotes opsonization,
neutralization and cross-linking of antigens - only Ig that crosses
placenta - present in tissue fluids
IgG (monomer)
- present in tears, saliva,
mucus, and breast milk - provides localized defense
of mucous membranes by
neutralization and cross-linking of antigen
IgA (dimer)
- present on surface of B
cells that have not been
exposed to antigens - acts as antigen receptor in
the antigen-stimulated
proliferation and
differentiation of B cells
IgD (monomer)
- present in blood at low
concentrations - triggers release from mast
cells and basophils of
histamine and other
chemicals that cause
allergic reactions
IgE (monomer)
what do you call the condition/ hemolytic disease where in a mother is Rh- and the baby is Rh+. The mother’s Rh factor attacks the baby in the placenta?
Erythroblastosis fetalis
