Adaptive Immune system Flashcards
what is the adaptive immune system, what triggers it?
- triggered by the processes of innate immunity ie. phagocytosis and antigen presentation
- branch of immune system iwht memory - formed during an infectiona nd can last for years
**antigen specific - virutally limitless foreign antigen structures can be recognized
- causes amplification - hieghtened by subsequent exposures
- tolerance - distinugishes itself from foreign
**B and T lymphocytes
primary vs secondary exposure to an antigen
Takes a bit of time to get primary immune response, get amount you need to clear pathogen then disipates
Then if exposed again already have memory cells circulating and secondary immune response is faster and stronger
what happens when adpative immune system is missing?
- result of inheritable genetic mutation SCID (evere combined immunodeficiency syndrome)
- affects development of both B and T lymphocytes
- lack of the 2nd line of defense against all invaders
*would relay fully on innate immune system
what are the two major cell types of the apative immune system and where did they differentiate from?
stem cell differentiates into myeloid and ymphoid stem cells
- lymphoid stem cells then diff into B lymphocytes (produce antibodies/immunoglobulins) and T lymphocytes (Helpter T cells, Cytotoxic T cells and regulatory T cells)
B lymphocytes mature in the ______ and T cells mature in the ______
B lymphocytes matture in bone marrow
T lymphocytes matture in thymus
what are hematopoietic stem cells?
- from red bone marrow
- origin of multipotent hematopoietic stem cells that then can diff into myeloid and lymphoid cells
what are the two types of adaptive immunity
Humoral Immunity
- invovled B cells (B lymphocytes)
- produce antibodies (immunoglobulins) that directly target invaders and their products in the body fluids (humors)
Cell mediated immunity
- involve diff types of T cells (T lymphocytes)
- T cells work together to
- recognize antigens displayed on infected cells
- target intracellular infections -directly kill infected cells
- provide help to B-, T- and antigen presenting cells
**humoral and cell mediaed immunity are intertwined
what triggers the adaptive immune response?
- immune system does not recognize whole microbes/viruses, but tiny pieces of them called antigenic determinants or epitopes
*epitope can be as small as 9 aa or longa s 25 aa
- B- and T-cells recognize different types of epitopes
- al receptors on a B or T cell recognize ONE specfiic epitope (monospecific)
- each epitope is recognzied by a different B and T cell
*response to a microbe involved thousands of different B and T cells
what do antigents stimualte and what does that do
antigens stimulate B cells to differentiate into antibody producing cells
*antigens have a few or multiple different epitopes
- epiotes are often described as linear or confirmational
what is immunogenicity?
- the effectiveness by which an antigen elicites an immune resposne
*proteins are better immunogens bc fo size, uniqueness, can be transported into cell
compare immunogens and haptens
immunogen = antigen that can elicit an antibody production by themselves
Hapten = small molecule that are not immuniogenic on their own, much be convalently attached to a large carrier protein or other molecules
* if injected with a hapten and see no respond link with a protein complex
what is immunogeni specificity? what is cross binding?
an antibody made to one epitope will not bidn to otehr epitopes
- cross binding can occur with similar epitoes
ex: antibodies of cowpox virus wil bind to a similar epitope on the small pox virus neutralizing the virus - technique used in vaccination
what is cross protection?
cross protection will onyl work if two proteins ciritcal to the pathogenesi of the two different microorgnisms share ket antigenic determinants (required for infection of host cell)
- no cross protection occurs if these determinants differ significatnly
what is the ABO blood group system a good example of
- immunological specificity
- individuals with type A antigen on their RBCs posses anti B antibodies
*react to the B and not the A antigens
describe the antibody/immunoglobulin monomer
- Y shaped structure made of 4 polypeptides
- 2 identical large heavy chains and two identical smaller light chains -each arm of the Y is composed of one heavy and one light chain
- each arm has one epitope bindind site; a total of 2 sites per antibody monomer
- chains are connected by disulfide covalent bonds between the heavy chains and between each heavy and light chain
what are the two regions on the antibody/immunoglobulin monomer
constant (C) and ariable (V) regions
- constant regions are highly conserved amino acid sequences
- varibale regions are hgihly different/variable amino acid sequence
*variable region can generate antibodies that will bidn to endless number of antigens
- the variable regions of BOTH the L- and H- chains (VH & VL) form the epitope binding site/pocket
- functional parts of the antibody - Fab and Fc regions can be separated following cleavage by certain enzymatic enzymes
*Fc faciliates opsonization
what is an isotype, what are the different ones?
*isotype refers to the antibody class
- defined by the heavy chain there are 5 types”
γ = IgG monomer, 2 antigen binding sites
δ= IgD monomer 2 antigen binding sites
α= IgA dimer with secretory component 4 antigen binding sites
μ= IgM pentamer 10 antigen binding sites
ε = IgE monomer 2 antigen binding sites
- each isotype if common to a species - IgA is the same fro all humans but diff from that of a a cow or mouse
describe neutralization and agglutination
- Neutralization
* binding of specific antibodies to antigens, preventing attachment to target cells - Agglutination
* antibodies agglytinate pathogens by binding to epitopes on two or more microbes simultaneously (aggregation)
describe opsonization
- effector function of antibodies
- enhances phagocytosis
- IgG is an opsonin ( as is complement factor C3b)
- Fc of a ‘free’ IgG is not recognized by the Fc-receptor in phagocytes
- when bound to an antigen/epitope, the Fc domain undergoes ocnformational change to reveal the Fc receptor binding domain
describe complement dependent cytotoxicity
- via the calssical complemnt pathway
*invovles antibody-antigen complex that activates the pathway
- antibody (IgG or IgM) binds tot he surface of a pathogen (opsonization)
- complement C1 binds to the Fc-domain of the antibody
- initiates activation of the complement via classical pathway
*bound C1 is activated which activates C2, C4 and C3…
*pathway converges with that previously descriebd for alternate pathway
what are the two claasses of MHC
Class 1: found on all nucleated body cells (NOT RBC)
- presents inracellular antigens - include both host (self) and non self (intracellular bacterial pathogens or viral proteins)
- proteins made in the host cytoplasm are degraded
- peptides are imported itno the ER and loaded onto MHC class I mol
Class II: found only on antigen presenting cells (APCs like monocytes, macrophages dendritic cells and B cells)
- microbes and foreign protens frmo outside the host cell are taken up (phagocytosis and endocytosis) by APCs
- they are then degraded and placed on the MHC class II molecules
* be able to label the figure
