Unit 4 Flashcards
Where do B cells mature in?
Bone marrow
Where do T cells mature in?
thymus
The _______ immune system can stimulate the ________ immune system by which 2 WBC?
innate, adaptive, neutrophil and macrophages
Which leukocytes are APCs (antigen presenting cells)?
Neutrophils, macrophages, B cells. Using MHC-II, they display the antigens of phagocytized pathogens on their surface
How do B cells contact antigens?
Either contact antigen directly or on the surface of an APC
Function of helper T cells (TH)
do not play an active role in the immune response; activate B cells and T cells so that they can get in contact with APCs bearing antigens
Both T cells and B cells form what 2 kind of cells?
memory cells and effector cells
Plasma B cells:
effector B cells make antibodies
Cytotoxic T cells (Tc)
effctor T cells attack the pathogen directly
What are the 4 functions of antibodies
agglutination, neutralization, opsonization, complement activation
Agglutination:
some Abs stick together, causing target to clump
Neutralization:
bind to the surface of a pathogen, toxin and prevent its function
Opsonization:
cell bound by antibodies are more often phagocytized
Where are MHC I? and MHC II?
All nucleated human cells; some types of WBC (APC: neutrophils, macrophages, B cells)
Two classes of antigens:
1) those expressed within normal cells and presented on the surface by MHC-I
2) Those derived from phagocytosis by APCs and presented on the surface by MHC II
Antigen:
specific molecule (usually protein) that may be used by the immune system to identify a specific pathogen. Substance that bind to lymphocyte (B/T cell) receptors (ex. antibodies)
Epitope:
the segment of an antigen that is specifically recognized by lymphocyte receptors
Immunogens:
agents that can provoke an immune response (i.e. immunogenic) and react with the products of such repsonse
Antigens that are NOT immunogens:
1) haptens, 2) too similiar to normal cellular proteins, 3) do not have static structure and/or repeating structure
Examples of haptens
sugars, amino acids, and drugs and/or drug metabolities (e.g. penecillin degrades, it can react with proteins)
Example of antigen that is too similar to normal protein
Streptococcus pyogenes: has cell surface proteins that resemble normal human proteins - “molecular mimickry”
Antigens that are NOT immunogens: structure examples
1) lipids and globular proteins have slimy, dynamic structures and are poorly immunogenic. 2) Starch, glycogen and other polysaccharides are repearting strcutures and are poorly immunogenic
Antigen: chemical composition (highly to least immunogenic)
(highly immunogenic) proteins > carbohydrates > pure lipids (least)
Antigen: molecular size
macromolecules with higher molecular weights are more immunogenic
Antigen: structural complexity
Aromatic molecules are more immunogenic than alipathic molecules. (Scented products causes more of an allergic rxn, than non-scented products or hypoallergenic)
Antigen: genetic disparity
Things that are different/foreign in a a host is immunogenic
(e.g. horse Abs against botulism toxin - antitoxin for humans leading to serum sickness)
Autograft
from self
Isograft
from twin
Allograft
from unrelated person
Xeongraft
from animal
Autoantigens
modification of normal proteins, stimulation of autoimmune response can cause normal proteins to become recognized as antigen
Alloantigens
antigens derived from other people
- (e.g. blood transfusion: blood group antigens A B Rh;
- organ transplant: human leukocyte antigens (HLAs - tissue type))
Minimizing genetic disparity risk (3)
- Umbilical cord blood biobanking: cord blood is rich in hematopoietic stem cells.
- Authologous bone marrow transplant (ABMT): for pts with leukemia, bone marrow harvested during remission and stored. during relapse then can receive their own bone marrow.
- Autologous blood transfusion: elective surgery, receive own blood
Cardiolipin
found in surface of bacteria such as syphilis and also surface of mitochondria. In lupus, antibodies are made that can go inside the cell, cardiolipin because an autoantigen
Extrinsic immunogenic facotrs: adjuvants
agents added to vaccines to enhance the vaccines’ immunogenicity (e.g. alum and dead bacteria as well as oil-in-water emulsion) (squalene in H1N1)
Epitopes aka
immunogenic or antigenic determinants. part of immunogen/antigen that interact with antigen-binding site of antibody/ T cell receptor (TCR). sequence of 4-6 amino acids = sufficient epitope. 3D shape is more important that the amino acids. agent must contain more than one epitope in order to be immungenic. identification of epitopes on an immunogen can have clinical significance (e.g. production of vaccines and monoclonal antibodies)
Immunoglobulins
receptors on the surface of B/T cells
VDJ
variable diverse joining
Active immunity:
the body exposed to an immunogen that stimulates the immune response
Naturally acquired active immunity:
exposure to pathogen
Artificially acquired active immunity:
exposure to vaccine
Passive immunity
individual receives protective immune products (ex. Abs) - no immunological memory! (aka passive immunization)
Naturally acquired passive immunity
Abs from mother through placenta or breastfeeding
Artificially acquired passive immunity
premade Abs - serum of an immune donor, purified immunoglobulins
How is antivenom made?
Venom is obtained from snake by milking, diluted and injected into a horse. Abs are purified from the horse serum.
VDJ
variable diverse joining
Active immunity:
the body exposed to an immunogen that stimulates the immune response
Naturally acquired active immunity:
exposure to pathogen
Artificially acquired active immunity:
exposure to vaccine
Passive immunity
individual receives protective immune products (ex. Abs) - no immunological memory! (aka passive immunization)
Naturally acquired passive immunity
Abs from mother through placenta or breastfeeding
Artificially acquired passive immunity
premade Abs - serum of an immune donor, purified immunoglobulins
How is antivenom made?
Venom is obtained from snake by milking, diluted and injected into a horse. Abs are purified from the horse serum.
Prophylaxis
administer an agent to prevent disease before exposure has occured
4 Sources of antigens
1) killed whole cell or inactivated virus 2) live, attenuated cells or virus 3) proteins or other antigenic molecules purified from pathogen 4) genetically engineered antigen
Killed/inactivated pathogen (antigen)
- pros + cons
- 2 examples
- pathogen is killed by heat, radiation, or chemical treatment (ex. salk polio, influenza)
- pro: almost always dead and safe.
- con: does not multiply, higher dose & booster shots needed
attenuated pathogen (antigen)
- pros + cons
- 3 examples
- pathogen is grown in lab conditions until they lose virulence
- (eg. BCG (Tuberculosis) - 13 years of cultivation;
- OPV - oral polio vaccine;
- toxoid attenuated exotoxin such as diptheria, tetanus)
- pros: multiplies somewhat, confer long-lasting protection
- cons: small risk of reversion (1 over 1-3 million)
Purified molecules (antigen) pros + cons
- fragments or purified components of pathogen used, rather than living organism
- anthrax, hep B
- pros: no living pathogen
- cons: antigen may change shapre during purfication
Recombinant protein (antigen) pros + cons
- DNA encoding the protein of a pathogen is expressed in yeast
- e.g. Hep B
- pro: cheap, safe
- con: clonal, pathogen can evolve resistance easily
Check list of requirements for an effective vaccine
- it should hav ea low level of adverse side effects or toxicity and not cause serious harm
- it should protect against exposure to natural, wild forms of pathogen
- it shoudl stimulate both antibody (B cell) response and cell mediated (T cell) repsonse
- it should have long term, lasting effects (produce memory)
- it should not require numerous dose or boosters
- it should be inexpensive, have a relatvely long shelf life, and be easy to administer
Herd immunity
- scale immunization campaign should be targeted to at-risk population (e.g. infants and children at high risk of common childhood disease/infections) - cost-effective and benefits outweighs the risk
- large scale immunization is often used to prevent epidemic by establishing a high level of herd immunity in a population (e.g. typically when over 95% of the people in the popluation are immune to the infectious agent of agent)
