Hummoral immunity (bowden)

Question 1

Humoral immunity

Answer 1

Branch of adaptive immunity mediated by antibodies produced by B cells (Plasma cells).

Humoral immunity is the principal defense against EXTRACELLULAR pathogens

Question 2

where are antibodies produced and what produces them?

Answer 2

lymhoid tissues/organs

Plasma cells (activated b cells)

Question 3

where is the effector function of the antibody?

Answer 3

Fc region

Question 4

what triggers Ab function?

Answer 4

Ag binding to Fab (V) region of the antibody

Question 5

Hyper IgM syndrome

Answer 5

pt is deficient in antibody responses to T-dependent Ags but can make IgM to antigens that are t-independent

usually show no germinal centers in their lymph node

cannot undergo class switching and cannot make memory B lymphocytes for long-term immunity

might have to do with defect in CD40 ligand expression on T cells so can’t switch to make IgG, IgE or IgA

prone to infections (such as PCP (pneumocytsis jiroveci pneumonia)

Question 6

Humoral immune response

Answer 6

Neutralization
Opsonization/waste management
Complement activation

Question 7

Neutralization

Answer 7

Ab neutralize the infectivity and potential effects of infection

only requires binding to antigen and any class works

prevents microbes from gaining enter into cells

the higher the affinity the antibody for the Ag epitope the better
used alot in vaccinations

Question 8

Opsonization and phagocytosis

Answer 8

Fc receptors on immune cell populations promote phagocytosis

opsonization is binding of Ab to microbe

binding of opsonized microbes to phagocyte Fc receptors

Fc receptors signals activate phagocytosis of microbe

killing of microbes

Question 9

ADCC

Answer 9

antibody-dependent cell mediated cytoxicity

can be mediated by NK cells, macrophages, eosinophils, etc.

Question 10

ADCC: anti-viral state

(NK cells)20 minutes since you saved your work.

Answer 10

NK cells express CD16 which binds to IgG that has bound to an antigen on the surface on an infected cel

this binding of CD16 with IgG (antibody) promotes killing of anti-body coated cell

Question 11

IgE mediated reactions

Answer 11

IgE binds to Fc receptors (CD23) present on mast cells

Ag binding causes degranulation of cell

usually for killing parasites (helminth)

Question 12

Activation of the complement system

Answer 12

in the classical pathway

IgM or IgG

Question 13

Blood group antigens

Answer 13

sugar groups found on bacteria in the gut

Question 14

toxoids

Answer 14

proteins that need t help for b cell activation

Question 15

why is IgG better than IgM and found in 30-50 x higher concentration in our bodies?

Answer 15

IgM can only promote phagocytosis of bacteria by activating the C’ system

IgG can stimulate phagocytosis by binding its Fc region to Fc receptor on phagocytes AND activates the complement system

Question 16

What else is CD40 expressed on?

Answer 16

Macrophages and dendritic cells

lack of CD40 signaling in Hyper IgM immunodeficiency leads to impaired handling of opportunist pathogens

also expressed on platelets and endothelium and epithelium cells during inflammation

Question 17

X-linked HyperIgM

Answer 17

CD40L deficiency
severely impaired production of IgG and IgA
no response to protein Ags
T-independent antigen response only
B memory cells absent or very reduced

Question 18

what does treatment with IvIg do for pt’s with autoimmune/inflammatory diseases?

Answer 18

engages the inhibitory FcR on B cells and possibly dendritic cells and suppresses the immune responses

Question 19

waste management

Answer 19

antigen/antibody immune complexes form

activation of complement leads to deposition of many C3b on the immune complex

Complement receptor (CR1) on RBC’s binds the IC

In the spleen and liver, phagocytic cells remove the immune complexes from the RBC surface

Question 20

Chronic infection can lead to ….

Answer 20

immune complex disease

persistent immune response to antigen can lead to formation of immune complexes

immune complexes themselves may become immunogenic (RA factor)

Question 21

what does positive rheumatoid factor mean?

Answer 21

the pt is making anti-IgG IgM

so making their own IgM against their own IgG

Question 22

cryoglobulins

Answer 22

IC’s and proteins may precipitate at s in the kidneys, small blood vessels and other organs

associated with hep C

Question 23

Polyclonal B cell response

Answer 23

polyclonal responses of B cells means each B cells is secreting monoclonal Abs specific to a different part of the virus

confers greater likelihood of clearance of Ag

Question 24

what happens when cryoglobulin complexes deposit in the wall of blood vessels?

Answer 24

they active C’

release of C3a and C5a are chemotactic and recruit leukocytes (macrophages and neutrophils)

neutrophils and macrophages release enzymes causing damage to endothelial cells of basement membrane

Question 25

Treatment for cryoglobulenemia using CD20 does what?

Answer 25

this is an antibody that targets CD20 which is on B cells

targets B cells for death

it is risky b/c it is taking out the entire B cell population