Unit 4- Specific Resistance (Adaptive Immunity) Flashcards
where do B-cells mature?
in the bone marrow
where do T-cells mature?
thymus
what are APCs?
antigen presenting cells
what cells are professional APCs?
neutrophils, macrophages, T-cells and B-cells
how do APCs display antigens?
using the protein complex MHC-II, they display Ags of phagocytized pathogens on their surface
how do B-cells contact an antigen
either directly, or on the surface of an APC, then they make antibodies in response
what do helper T-cells do?
they activate B_cells and T-cells (act as managers/match-makers)
2 types of B-cells?
memory B cells, plasma B cells (the effector cells, making antibodies)
2 types of T cells?
memory T cells and cytotoxic T cells (Tc)- teh effector T cells attacking pathogen directly
effector cell of B cells are called…
plasma B-cells
effector cell of T cells are called.
cytotoxic T cells (Tc)
what do Abs do?
ANOC out punch!!
1) Agglutination
2) Neutralization
3) Opsonization
4) Complement Activation
aggultination?
some Abs stick together, clumping the target
neutralization
Abs bind the surface of a pathogen, toxin and prevent its function (prevents pathogen from moving fwd by piling on top)
opsonization
Ab-bound cells are more often phagocytized
complement activation
complement factors poke holes (MACs) to lyse membrane
MHC stands for…?
multihistocompatibility complex; it takes proteins from digested bacteria and presents on surface of a neutrophil
2 classes of MHC
MHC Class 1- foudn on all human nucleated cells MHC class II- found on some types of WBCs (the antigen presenting cells)
what are MHC genes known as?
HLA genes
antigen
substances, specific molecules usually proteins, that bind to lymphocyte receptors (B/Tcell)
epitope
the segment of the antigen that is recognized by lymphocyte receptors (shape is recognizable)
immunogens
agents that can provoke an immune response and react with the prodcts of that response
what antigens are not immunogens?
1) haptens (when they’re too small)
2) when they’re too similar to normal cellular proteins
3) when they either don’t have a static structure, or have a highly repeating structure
haptens
are too small, and cannot elicit an immunological response, although bound to T/B cells. HOwever, they can bind to larger molecules (carriers)
example of an antigen that isn’t immunogenic because of similarity to normal cell proteins?
streptococcus pyogenes- molecular mimickry
what antigens have a changing structure?
lipids and globular proteins with slimay, dynamic structures… they’re poorly immunogenic
what antigens have a repeating structure?
starch, glycogen and other polysaccharides. they’re poorly immunogenic
what 6 factors determine immunogenicity of an Ag?
chemical composition, size, complexity, genetic disparity, and processing by APCs
proteins, carbohydrates, pure lipids— rate on immunogenicity
proteins are highly immunogenic, carbs are weakly and pure lipids are non-immunogenic
pattern of size and immunogenicity of Ag?
larger the size, greater the immunogenicity
structural complexity and immunogenicity of Ag?
greater the complexity, greater the immunogenicity
what structure of Ag molecules are almost most immunogenic?
aromatic molecules (as compared to alipathic molecules)
autograft
transplant from self
isograft
transplant from twin
allograft
transplant from unrelated person
xenograft
trasnplant from animal (different species)
autoantigens
when your own proteins becoem immunogenic and recognized as an antigen–> autoantibodies are produced
alloantigens
antigens derived from other people (ie. blood transfusion or organ trasnplant)
what are 2 ways of minimizing risk of genetic disparity?
1) umbilical cord blood biobanking– cord blood rich in hematopoietic stem cells)
2) autologous blood transfusion- bank your own blood prior to surgery so you could receive your own blood for transfusion
adjuvants
factors external to the substance that can make an Ag more immunogenic. Adjuvants are agents added to vaccines to enhance the vaccines’ immunogenicty
example of an adjuvant
alum and dead bacteria, as well as oil-in-water emulsion (clumps molecules together) while alum stimulates chemotaxis
components of a vaccine:
1) Ag (primary
2) Adjuvant
3) Preservative
epitope
immunogenic or antigenic determinants, they are part of immunogen/antigen that interact with the ag-binding site of the antibody/T-cell receptor, around 4-6 a.a. long
what’s the most important part of an epitope?
its 3D shape
immunoglobulins
receptors on the surface of B-cells and T-cells
lymphocyte immunoglobins mutate during when?
hematopoiesis
what is the result of immunoglobulin mutation?
immunoglobulin Ag binding site changes shape.. final shape is random depending on mutation
VDJ Recombination
genetic recombination that consists of 3 genes: Variable, Diverse, Joining.
how many possible epitopes are there as a result of VDJ Recombination?
3 x 10^11 epitopes
example of naturally acquired active immunity
exposure to pathogen
example of articficially acquired active immunity
exposure to vaccine
example of naturally acquired passive immunity
breast feeding/Abs from mother’s placenta
example of artificially acquired passive immunity
premade Abs from immune donor or purified IgGs
what Abs do mother’s pass to babies through breast feeding?
IgA, but it eventually runs out and baby needs to develop own immune system
prophylaxis
administer an agent to prevent disease before exposure has occured
source of antigens? 4
killed whole cell or inactivated virus, lived, attenuated cells/virus, proteins or other antigenic molecules purified from pathogen, genetically engineered antigen
pros and cons of killed/inactivated pathogens?
pros: almost always dead/safe. cons: does not multiply, higher dose and booster shots needed
pros and cons of attenuted pathogen
pros: multiples somewhat, long lasting protection. cons: small risk of reversion to active pathogen
examples of attenuated pathogenvaccines
BCG (Tb), OPV (oral polio vaccine), toxoid (Td)
pros and cons of purified molecules
pros: no living pathogen, cons: ag may change shape during purification
examples of purified molecules
anthrax, hep B
pros and cons of recombinant proteins
pros: cheap, safe; cons: clonal, pathogen can evolve resistance easily (it only represents one protein)
herd immunity
when over 95% of people in the population are immune to the infectious agent
