Acquired Immunity-Antibodies

Question 1

What type of cells secrete antibodies?

Answer 1

B cells
only cells in the body that are capable of making antibodies or immunoglobulins

Question 2

What neutralizes toxins?

Answer 2

Antibodies bind to and neutralize toxins
antibodies neutralize toxins
toxin-antitoxin antibody complex cannot bind to target cells

Question 3

What inactivates/prevent adherence and infections?

Answer 3

Antibodies bind to ectracellular bacteria and viral particle and inactivate/prevent adherence and infection
antigen:antibody complex is recognized by macrophages, internalized and eventually degraded.

Question 4

Coating of antigen by antibody

Answer 4

opsonization

Question 5

Antigen:Antibody complex can activate

Answer 5

complement system, which destroy antigen by lysis
antibodies bind to aged and damaged cells. macrophages have Fc receptors which phagocytose antibody-coated damaged cell and aid in clearance of old cells to keep the cell numbers in body optimum

Question 6

Pathological role of antibodes

Answer 6

when B cells become tumorigenic, cancer results(myeloma)
antibodies against self antigens (autoantibodies) destroy self tissues (autoimmune disease)
antibodies provoke exaggerated/inappropriate response

Question 7

Myeloma

Answer 7

plasma cell tumors
arise from single precursor cell or clone so secrete homogenous immunoglobulins of any class called myeloma proteins

Question 8

Autoantibodies against red blood cells

Answer 8

bind to RBC and destroy them through complement-mediated damage or opsonization (facilitate phagocytes to engulf better) antibodies

Question 9

Autoantibodies against synovial membrane and joint tissue

Answer 9

(rheumatoid factor) induce arthritis

Question 10

Type 1 hypersensitivity

Answer 10

IgE and eosinophils

Question 11

IgE

Answer 11

mediated allergic response

Question 12

Primary lymphoid organs

Answer 12

development occurs-no antigen interaction

Question 13

secondary lymphoidorgans

Answer 13

no further development of lymphocytes-site of antigen interactions

Question 14

B cell development and differentiation

Answer 14

stem cell-Pre B cell (cytoplasmic mu chain)-immature B cell (membrane bound IgM and IgD)-mature B cell-memory cell or plasma cell (immunoglobulin secretion)

Question 15

B cells have dual functions

Answer 15

secrete antibody (or immunoglobulin) production
antigen processing and presentation
antibodies play a critical role in defending against extracellular pathogen
antibodies cannot penetrate inside a cell, therefore not effective against intracellular pathogens

Question 16

Antibodies exist in two forms

Answer 16

secretory and membrane bound (Surface)

Question 17

secretory

Answer 17

detected in fluids such as serum, peritoneal cavity, mucosal fluids (humors) etc
(antibodies or immunoglobulins) found in body fluids (humors)

Question 18

membrane bound (surface)

Answer 18

important for specific binding to antigens
on B cell surface as B cell receptor (BCR)

Question 19

Secretory/free form of antibody

Answer 19

is found in the blood and body fluids as immunoglobulin. they neutralize antigen and assist in their removal
antibodies recognize free antigens( do not require combination with <HC unlike T cells)
antibodies are specific: bind speficially to antigen which induce antibody production
cannot penetrate the cell

Question 20

Antibody structure

Answer 20

they are glycoproteins made of 4 polypeptide chains
have a flexible y shaped structure

Question 21

Antibodies recognize shape of antigen

Answer 21

shapes of antigen and CDR(complementary determining regions of antibody)
each V region is folded in such a way that 3 CDRs come into contact with the antigen-creates a unique seat for antigen to sit

Question 22

Fc site

Answer 22

for complement binding

Question 23

Fc binds to

Answer 23

Fc receptors on cell surface

Question 24

Antibody or Immunoglobulin classes or Isotypes

Answer 24

based on heavy chain characteristics, antibodies are divided into 5 classes
IgM-mu
IgG-gamma
IgA-alpha
IgE-epsilon
IgD-delta

Question 25

IgM

Answer 25

first antibody to appear in circulation (predominant in primary antibody response largest in size membrane bound form is a monomer, secretory form is a pentamer has a J chain second highest in serum immunoglobulin level

Question 26

IgM function

Answer 26

agglutinate antigen Neutralize antigen

Question 27

IgG

Answer 27

most abundant monomer smallest can cross placenta in some species (primates and small percent in dogs and cats) can move out of the blood stream and is found in tissue, blood vessels and other secretions

Question 28

IgG function

Answer 28

Agglutinate antigen neutralize antigen important in inflammation

Question 29

IgA

Answer 29

Has a secretory component (sigA) which allows IgA to appear in secretions and protected from digestion by proteases prevents adherence of pathogen and antigen in general to mucosal surface and agglutinates tends to be synthesized under intestinal, respiratory, reproductive and other mucosal surfaces survive in harsh environment \

Question 30

IgE

Answer 30

monomer heavier than IgG bound to mast cells and basophils (tissue and blood respectively) through a receptor Fc Important in allergic reaction

Question 31

IgD

Answer 31

monomer similar to IgG BCR bound only secretion-negligible found in human, rats and mice

Question 32

Reasons to class switch

Answer 32

IgM to IgG (IgG is the only antibody which can penetrate placenta and blood vessels) IgM to IgA (IgA is the only antibody that survive in mucosal sites that is enzyme rich and acidic) IgM to IgE (IgE induces allergic type 1 hypersensitivity reaction)

Question 33

Class switch-antibody retains specificity

Answer 33

during an antibody response, class switch, occurs in standard sequence as immune response progrsses, B cells switches in presence of Th1 or Th2 cytokines and co-stimulatory molecules to one of the major secretory class Fab does not change during class switch

Question 34

B cell receptor (BCR) recombination

Answer 34

BCR determines the specificity of B cells BCR binding to salmonella antigen is different than BCR binding to E.Coli

Question 35

All B cells express

Answer 35

B cell receptors (binds specifically to antigen) CD19 (binds to C3d-decrease the threshold for B cell receptor signaling pathways) CD40(receptor for CD40L (or CD154) on activated T cells)

Question 36

Th2 cytokines act on B cells

Answer 36

Th2- cells secrete cytokines that initiate B cell activation and differentiation IL-4 induces class switch (IgM-IgE) enhances MHC class II and Fc receptor expression IL-5 acts on activated B cells to differentiate into plasma cells (antibody secreting cells, not present in plasma) Il-13 similar function as IL-4 IL-6 final differentiation of activated B cells into plasma cells

Question 37

Summary-B cells surface markers

Answer 37

B cell receptor (immunoglobulin/antibody-membrane bound) CD19 complex binds with complement C3d CD40-binds to CD40L on T cells CD68 binds with CD28 on T cells MHC class I and MHC class II antigen processing and presentation Th2 cytokine receptors such as IL-4R