immune Flashcards
Inappropriate immune responses lead to
** allergies**
or
**autoimmune responses **
The primary pathogens are
bacteria and viruses.
are non-nucleated, single-celled micro-organisms
Bacteria
are non-nucleated, single-celled micro-organisms
are not cellular, consisting of a nucleic acid enclosed by a protein coat
**
Viruses**
are not cellular, consisting of a nucleic acid enclosed by a protein coat
Effector Cells
Never
Let
Monkeys
Eat
Banannas
are highly mobile phagocytes
**Neutrophils **
secrete chemicals that fight parasites
Eosinophils
release histamine
Basophils
change into macrophages (resident phagocytes)
Monocytes
Lymphocytes are of two types
B lymphocytes
T lymphocytes
lymphocytes
change into plasma cells that make antibodies
B lymphocytes
Lymphocyte
are responsible for cell-mediated immunity
T lymphocytes
A given leukocyte is present in the blood only ____________. Most are in the_______ on “defense missions”
A given leukocyte is present in the blood only _transiently. _ Most are in the tissue on “defense missions”
Most leukocytes arise directly from
** stem cells in the bone marrow**
Lymphocytes arise from lymphocyte colonies in
lymphoid tissue
Two Intrinsic Defense Systems
- Innate (nonspecific) system
- Adaptive (specific) defense system
Innate (nonspecific) system responds quickly and consists of:
- First line of defense
- Second line of defense
– skin and mucosae prevent entry of microorganisms
First line of defense
antimicrobial proteins, phagocytes, and other cells
Second line of defense
Second line of defense – antimicrobial proteins, phagocytes, and other cells DO WHAT?
Inhibit spread of invaders throughout the body
Second line of defense – its most important mechanism
Inflammation
Adaptive (specific) defense system
THAT
– mounts attack against particular foreign substances
Third line of defense –
Adaptive (specific) defense system
Takes longer to react than the innate system &
Works in conjunction with the innate system
Third line of defense –
Adaptive (specific) defense system
Third line of defense – mounts attack against particular foreign substances
HUMORAL IMMUNITY CONTAINS-
B CELLS
Adaptive (specific) defense system
Third line of defense – mounts attack against particular foreign substances
CELLULAR IMMUNITY CONTAINS
T-CELLS
Skin
_________ (pH of 3 to 5) inhibits bacterial growth
Acidity
Skin
___________contains chemicals toxic to bacteria
Sebum
_______in the skin:
Presents a physical barrier to most microorganisms
Is resistant to weak acids and bases, bacterial enzymes, and toxins
Keratin
Mucosae provide similar ________ barriers
mechanical
Mucosae provide similar mechanical barriers
Stomach mucosae secrete concentrated_______ and protein-digesting enzymes
HCl
Mucosae provide similar mechanical barriers
Saliva and lacrimal fluid contain ________
- lysozyme
- *
Mucosae provide similar mechanical barriers
traps microorganisms that enter the digestive and respiratory systems
Mucus
Mucosae provide similar mechanical barriers
Respiratory tract mucosae
_____________ in the nose trap inhaled particles
Mucosa of the upper respiratory tract is _________
______ sweep dust- and bacteria-laden mucus away from lower respiratory passages
- Mucus-coated hairs in the nose trap inhaled particles
- Mucosa of the upper respiratory tract is ciliated
- Cilia sweep dust- and bacteria-laden mucus away from lower respiratory passages
The body uses nonspecific cellular and chemical devices to protect itself
- 3.
- Phagocytes and natural killer (NK) cells
- Antimicrobial proteins in blood and tissue fluid
- Inflammatory response
derived from monocytes) are the chief phagocytic cells
Macrophages
wander throughout a region in search of cellular debris
Free macrophages
are fixed macrophages
Kupffer cells (liver)
and
microglia (brain)
become phagocytic when encountering infectious material
Neutrophils
are weakly phagocytic but important against parasitic worms
Eosinophils
- adherence more efficient if complement proteins or antibodies coat microbe
Opsonization -
Microbes adhere to the phagocyte by
“signature” carbohydrates
Phagocytosis
Pseudopods engulf the particle into a
Phagosomes
Phagocytosis
Phagosomes fuse with a lysosome to form a
phagolysosome
Phagocytosis
Invaders in the phagolysosome are digested by
proteolytic enzymes
Phagocytosis
Indigestible and residual material is removed by
exocytosis
Macrophages and other phagocytic cells have this &
recognize specific classes of infecting microbes
Toll-like Receptors (TLRs)
Binding TLRs promotes phagocytosis and triggers the release of ________that promote inflammation
cytokines
React nonspecifically and eliminate cancerous and virus-infected cells
Natural Killer (NK) Cells
Natural Killer (NK) Cells
Kill their target cells by releasing _______and other cytolytic chemicals
*Same method as Cytotoxic T lymphocytes
perforins
Natural Killer (NK) Cells
Also secrete chemicals that enhance the
inflammatory response
The four cardinal signs of acute inflammation are
redness, heat, swelling, and pain
Inflammation Response
Flood of inflammatory chemicals released into
extracellular fluid
Remember activated TLRs trigger the release of cytokines that promote inflammation
Cytokine =
cell to cell signaling molecule
Inflammation Response
WHAT IS released from basophils and mast cells in response to physical injury
Histamine
Inflammation Response
WHAT IS released by injured tissue
Prostaglandins
Inflammation Response
Cause local small blood vessels to dilate, resulting in
hyperemia
Inflammatory Response: Vascular Permeability
Chemicals liberated by the inflammatory response ______ the permeability of local capillaries
increase
Inflammatory Response: Vascular Permeability
—fluid containing proteins, clotting factors, and antibodies
Exudate—
___________seeps into tissue spaces causing local edema (swelling), which contributes to the sensation of pain
Exudate
The surge of protein-rich fluids into tissue spaces :
- Helps dilute harmful substances
- Brings in large quantities of oxygen and nutrients needed for repair
- Allows entry of clotting proteins, which prevents the spread of bacteria
(edema):
Inflammatory Response: Phagocytic Mobilization
Inflammatory chemicals diffusing from the inflamed site act as
chemotactic agents
Inflammatory Response: Phagocytic Mobilization
4 main phases
- Leukocytosis
- Margination
- Diapedesis
- Chemotaxis
– neutrophils are released from the bone marrow in response to leukocytosis-inducing factors released by injured cells
Leukocytosis
– neutrophils cling to the walls of capillaries in the injured area
Margination
– neutrophils squeeze through capillary walls and begin phagocytosis
Diapedesis
– inflammatory chemicals attract neutrophils to the injury site
Chemotaxis
Antimicrobial Proteins
Enhance the innate defenses by:
- Attacking microorganisms directly
- Hindering microorganisms’ ability to reproduce
Antimicrobial Proteins
The most important antimicrobial proteins are:
- Interferon
- Complement proteins
Genes that synthesize IFN are activated when a
host cell is invaded by a virus
Interferon molecules leave the infected cell and enter
neighboring cells
Interferon stimulates the neighboring cells to activate genes for an
antiviral protein
The antiviral protein nonspecifically blocks ________in the neighboring cell
viral reproduction
Complement System
Can be activated in two ways
- By exposure to molecules microorganisms surface
- By exposure to antibodies (next lecture)
Complement System
Does two things
- Formation of Membrane Attack Complex that kills microbes
- Augmentation of the inflammation
Complement can be activated by two pathways:
- Classical pathway
- Alternative pathway
Antibodies bind to invading organisms
C1 binds to the antigen-antibody complexes (complement fixation)
Classical pathway
Triggered by factors B, D, and P, and polysaccharide molecules present on invading organisms
Alternative pathway
Both pathways(classical&alternative)
converge on ____, which cleaves into C3a and C3b
C3
______ initiates formation of a membrane attack complex (MAC)
C3b
MAC causes cell ______ by allowing influx of water
lysis
C3b also causes_________,
and
C3a causes________
opsonization
and
nflammation
The body’s thermostat is reset upwards in response to ____________, chemicals secreted by leukocytes and macrophages exposed to bacteria and other foreign substances
** pyrogens **
High fevers are dangerous because they can
denature enzymes
Moderate fever can be beneficial, as it causes:
The liver and spleen to sequester iron (needed by microorganisms)
An increase in the metabolic rate, which speeds up tissue repair
Why is Adaptive (Specific) Defenses
a functional system?
- Recognizes specific foreign substances - particular pathogens or foreign substances
- Is systemic - not restricted to initial infection site
- Has “memory” - after initial exposure, second response is stronger and faster
- Also amplifies inflammatory response and activates complement
adaptive(specific) immune system has two separate but overlapping arms called
- Humeral, or antibody-mediated immunity
- Cellular, or cell-mediated immunity
Antibodies freely circualte in the blood and lymph
Bind bacteria, toxins, free viruses
Marking for destruction is known as what immunity?
Humeral, or antibody-mediated immunity
What immunity is -Living cells protect against …
Cells - infected with viruses, cancerous, from a graft
Cellular, or cell-mediated immunity
Compounds that elicit antibody production
Antibody generator
Antigens can be found on ?
surface of bacteria, on the surface of red blood cells, in pollens, in toxins, in food
Antigens can be an enormous variety of materials but
what induces strong response
Proteins and polysaccharides
Y-shaped protein that has two regions:
Antibodies
Antibodies 2 region names
Fc Region
Fab region
The constant region is the stem of the Y
Fc region
The two (identical) variable regions are the arms of the Y
(Fab region)
how can specific immunity be specific
variable region
(Fab region)
binds to a specific antigen
Two types of lymphocytes
B lymphocytes
T lymphocytes
types of lymphocytes
– oversee humoral immunity
B lymphocytes
type of lymphocytes
– non-antibody-producing cells that constitute the cell-mediated arm of immunity
T lymphocytes
Play essential auxiliary roles in immunity
Antigen-presenting cells (APCs):
Antigen-presenting cells (APCs):
what are the (professional APC)
- Macrophage,
- Neutrophil,
- Dendritic cells
Lymphopoiesis involves
bone marrow
thymus,
peripheral lymphoid tissue
All lymphocytes begin maturation in
bone marrow
- B cells finish maturation in the
- T cells finish maturation in the
- Mature but still “naïve” cells travel to
- bone marrow
- thymus
- peripheral lymphoid tissue
first encounter between an antigen and a naive immunocompetent cell
Antigen challenge
Humoral Immunity Response Antigen challenge Takes place in the
spleen or other lymphoid organ
If the lymphocyte is a B cell:
The challenging antigen provokes a ________ immune response
___________ are produced against the challenger
If the lymphocyte is a B cell:
The challenging antigen provokes a humoral immune response
Antibodies are produced against the challenger
– cellular differentiation and proliferation, which occurs on the first exposure to a specific antigen
- Lag period: 3 to 6 days after antigen challenge
- Peak levels of plasma antibody are achieved in 10 days
- Antibody levels then decline
Primary immune response
– re-exposure to the same antigen
- Sensitized memory cells respond within hours
- Antibody levels peak in 2 to 3 days at much higher levels than in the primary response
- Antibodies bind with greater affinity, and their levels in the blood can remain high for weeks to months
Secondary immune response
Active Humoral Immunity what encounters antigens and produce antibodies against them
B cells
response to a bacterial or viral infection
Naturally acquired –
response to a vaccine of dead or attenuated pathogens
Artificially acquired
spares us the symptoms of disease, and their weakened antigens provide antigenic determinants that are immunogenic and reactive
Vaccines –
Passive Humoral Immunity
Differs from active immunity in the antibody source and the degree of protection by
- B cells are not challenged by antigens
- Immunological memory does not occur
- Protection ends when antibodies naturally degrade in the body
Passive Humoral Immunity
- – from the mother to her fetus via the placenta
- – from the injection of serum, such as gamma globulin
- Naturally acquired – from the mother to her fetus via the placenta
- Artificially acquired – from the injection of serum, such as gamma globulin
Antibodies themselves do not destroy antigen; they
inactivate and tag it for destruction
All antibodies form an
antigen-antibody (immune) complex
Defensive mechanisms used by antibodies are:
- 4.
Defensive mechanisms used by antibodies are:
- Complement fixation
- Neutralization
- Agglutination
- Precipitation
Main mechanism used against cellular antigens
Complement fixation
This triggers complement fixation and cell lysis
Antibodies bound to cells change shape and expose complement binding sites
Remember, complement activation also:
- Enhances the__________response
- Uses a ______ feedback cycle to promote phagocytosis
- Enlists more and more ________ elements
Remember, complement activation also:
- Enhances the inflammatory response
- Uses a positive feedback cycle to promote phagocytosis
- Enlists more and more defensive elements
– antibodies bind to and block specific sites on viruses or exotoxins, thus preventing these antigens from binding to receptors on tissue cells
(mask dangerous parts of baterial exotoxins; viruses)
Neutralization
Cell bound antigens-
- antibodies bind the same determinant on more than one antigen
*Makes antigen-antibody complexes that are cross-linked into large lattices
Agglutination
soluble molecules are cross-linked into large insoluble complexes
Precipitation
Antibody Structure
consist of
___ polypeptide chains linked together with____bonds
Two identical heavy (H) chains and two identical light (L) chains
Four polypeptide chains linked together with disulfide bonds
Two identical heavy (H) chains and two identical light (L) chains
Each chain of the Antibody has a _____ region at one end and a_________ region at the other
Each chain has a variable (V) region at one end and a constant (C) region at the other
What part of the Antibody structure combines to form the antigen-binding site
Variable regions of the heavy and light chains
To code for this many antibodies,_______________takes place:
*Gene segments are shuffled and combined in different ways by each B cell as it becomes ____________
*Random mixing of gene segments makes unique antibody genes that:
Code for _____ of the H and L chain
To code for this many antibodies, somatic recombination takes place:
Gene segments are shuffled and combined in different ways by each B cell as it becomes immunocompetent
Random mixing of gene segments makes unique antibody genes that:
Code for V region of the H and L chain
Antibodies responding to different antigens have different _____ regions but the _____ region is the same for all antibodies in a given class
_____ regions form the stem of the Y-shaped antibody and determine the class of the antibody
** (V) Varible**
(C) Constant
(C) Constant
There are five classes of antibodies:
- ** IgD**
- IgM
- IgG
- IgA,
- IgE
– monomer attached to the surface of B cells, important in B cell activation
IgD
– pentamer released by plasma cells during the primary immune response
** IgM** – pentamer released by plasma cells during the primary immune response
– monomer that is the most abundant** and **diverse antibody in primary and secondary response; crosses the placenta and confers passive immunity
** IgG**
dimer that helps prevent attachment of pathogens to epithelial cell surfaces
** IgA** – dimer that helps prevent attachment of pathogens to epithelial cell surfaces
monomer that binds to mast cells and basophils, causing histamine release when activated
_ IgE_ – monomer that binds to mast cells and basophils, causing histamine release when activated
________ are primarily helper T cells (TH)
_____________ are cytotoxic T cells (TC) that destroy cells harboring foreign antigens
CD4 cells (T4 cells)
** CD8 cells** (T8 cells)
__________ proteins – found on virtually all body cells
_________ proteins – found on certain cells in the immune response
- *Class I MHC** proteins – found on virtually all body cells
- *Class II MHC** proteins – found on certain cells in the immune response
- Found on almost all cells
- Always recognized by CD8 cytotoxic T cells
-
Display peptides from endogenous antigens
*
Class I MHC proteins
- Found on B-cells and phagocytic cells
- Always recognized by CD4 helper T cells
- Display peptides from exogenous antigens
Class II MHC proteins
They circulate throughout the body in search of body cells that display forign antigen on MHC I
TC cells, or killer T cells, cytoxic cells
The four major types of grafts are:
The four major types of grafts are:
Autografts – Isografts – Allografts – Xenografts –
– graft transplanted from one site on the body to another in the same person
_ Autografts_ – graft transplanted from one site on the body to another in the same person
– grafts between identical twins
_ Isografts_ – grafts between identical twins
– transplants between individuals that are not identical twins, but belong to same species
Allografts – transplants between individuals that are not identical twins, but belong to same species
– grafts taken from another animal species
_ Xenografts_ – grafts taken from another animal species
Congenital and acquired conditions in which the _function or production of immune cells, phagocytes, or complement is abnormal
_
Immunodeficiencies
Immunodeficiency-
a genetic defect that producse:
*A marked deficit in B and T cells
Abnormalities in interleukin (chemokine that signals between WBCs) receptors
or
Defective adenosine deaminase (ADA) enzyme
Metabolites lethal to T cells accumulate
SCID – severe combined immunodeficiency (SCID) syndromes
SCID is _____ if untreated; treatment is with_____
SCID is fatal if untreated; treatment is with bone marrow transplants
Acquired Immunodeficiencies
– cancer of the lymph nodes leads to immunodeficiency by depressing lymph node cells
Hodgkin’s disease
– cripples the immune system by interfering with the activity of helper T (CD4) cells
Characterized by severe weight loss, night sweats, and swollen lymph nodes
Opportunistic infections occur, including pneumocystis pneumonia and Kaposi’s sarcoma
Acquired immune deficiency syndrome (AIDS) –
*Loss of the immune system’s ability to distinguish self from nonself
*The body produces autoantibodies and sensitized TC cells that destroy its own tissues
Autoimmune Diseases
Examples include multiple sclerosis, Type I (juvenile) diabetes mellitus, and rheumatoid arthritis
Autoimmune Diseases
Hypersensitivities categories:
- Immediate
- IgE-Mediated
- E.g., anaphylactic shock
*
- Type I
- *
Hypersensitivities categorie:
- Cytotoxic
- E.g., Blood transfusion reactions
*
- Type II
- *
Hypersensitivities categorie:
- Immune Complex (Ab/Ag)-Mediated
- E.g., Disseminated intravascular coagulation in Gram-negative septicemia
*
- Type III
- *
Hypersensitivities categorie:
- Delayed Cell-Mediated
- E.g., Tuberculin reaction
- Type IV
- *
- Caused by IgM and IgG (not IgE)
- Onset is slow (1–3 hours) after antigen exposure
- Duration is long lasting (10–15 hours)
Type II Hypersensitivities
- Antibodies bind to antigens on specific body cells, stimulating phagocytosis and complement-mediated lysis of the cellular antigens
- Example: mismatched blood transfusion reaction
Cytotoxic (type II) reactions
*Immune complexes are eliminated by phagocytosis
*with excess of antigen many small immune complexes are made
“block” small capillaries (e.g., in kidney)
Called Disseminated Intravascular Coagulation
Type III Hypersensitivities
Infection of blood (septicemia) by _________bacteria
Leads to LPS in blood, immune complexes
Infection of blood (septicemia) by Gram-negative bacteria
Leads to LPS in blood, immune complexes
Delayed hypersensitivities caused by cell-mediated immunity
Poison ivy and poison oak
Latex products
Tuberculin skin test
Type IV Hypersensitivities