Adaptive Immune system

Question 1

what is the adaptive immune system, what triggers it?

Answer 1

• 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

Question 2

primary vs secondary exposure to an antigen

Answer 2

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

Question 3

what happens when adpative immune system is missing?

Answer 3

• 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

Question 4

what are the two major cell types of the apative immune system and where did they differentiate from?

Answer 4

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)

Question 5

B lymphocytes mature in the ______ and T cells mature in the ______

Answer 5

B lymphocytes matture in bone marrow

T lymphocytes matture in thymus

Question 6

what are hematopoietic stem cells?

Answer 6

• from red bone marrow
• origin of multipotent hematopoietic stem cells that then can diff into myeloid and lymphoid cells

Question 7

what are the two types of adaptive immunity

Answer 7

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

Question 8

what triggers the adaptive immune response?

Answer 8

• 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

Question 9

what do antigents stimualte and what does that do

Answer 9

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

Question 10

what is immunogenicity?

Answer 10

• the effectiveness by which an antigen elicites an immune resposne

*proteins are better immunogens bc fo size, uniqueness, can be transported into cell

Question 11

compare immunogens and haptens

Answer 11

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

Question 12

what is immunogeni specificity? what is cross binding?

Answer 12

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

Question 13

what is cross protection?

Answer 13

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

Question 14

what is the ABO blood group system a good example of

Answer 14

• immunological specificity
• individuals with type A antigen on their RBCs posses anti B antibodies

*react to the B and not the A antigens

Question 15

describe the antibody/immunoglobulin monomer

Answer 15

• 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

Question 16

what are the two regions on the antibody/immunoglobulin monomer

Answer 16

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 (V_H & V_L) 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

Question 17

what if Fc and what does it do, what does it bind to?

Answer 17

• one of two functional regions of antibody
• facilitates opsonization
• bidns to phagocytes in IgG and mast cells and basophils in IgE

Question 18

what are the differnt types of heavy chains and the diff types of light chains?

Answer 18

5 diff heavy chains: : γ, δ, α, μ and ε

two diff light chains: λ and κ

Question 19

what is an isotype, what are the different ones?

Answer 19

*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

Question 20

what are the effector functions of antibodies

Answer 20

• enutralization, agglutination, opsonization, ADCC (antibody dependent cell mediated cytotoxicity) and complement dependent cytotoxicity

Question 21

describe neutralization and agglutination

Answer 21

1. Neutralization
   * binding of specific antibodies to antigens, preventing attachment to target cells
2. Agglutination
   * antibodies agglytinate pathogens by binding to epitopes on two or more microbes simultaneously (aggregation)

Question 22

describe opsonization

Answer 22

• 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

Question 23

what is ADCC

Answer 23

• antibody dependent cell mediated cytotoxicity
• opsonization (pathogens too large for phagocytosis ex parasites)
• Fc receptor binds to antigen and brings NK cells in close proximity
• release extracellular cytokines

Question 24

describe complement dependent cytotoxicity

Answer 24

• 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

Question 25

what is MHC and TCR

Answer 25

MHC = major histocompatibilty complex molecules TCR = T cell receptor, all T-lymphocytes ahve a membrane TCR (this is what recgonizes mol on surface of other cells) \*the diff T cell subtypes are identifiec by their function and accessort receptors

Question 26

describe MHC

Answer 26

- consists of transmembrane proteins with surface exposed variable regions wehre the antigen/epitope is bound - MHC proteins differ between species and amoung individuals within a species - they help to determine whether a given antigen is recognized as self or non self \*used to match tissue in transplants

Question 27

what are the two claasses of MHC

Answer 27

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