Lec 3 - Adaptive Immunity - Humoral

Question 1

Where do lympocytes come from and where do B and T cells mature?

Answer 1

stem cells in the bone marrow.

b cells mature in BONE MARROW.

t cells mature in THYMUS

Question 2

What are the B/T cell receptros?

Answer 2

B cell receptor - antibody.

Tcell - T cell receptor

Question 3

Where does antigen in/dependent differentiation take place?

Answer 3

in - central lympohoid tissue

dependent - peripheral

Question 4

What are the infections that B/T cells are effective against?

Answer 4

• B cells - extracellular bacteria, 2ndry viral
• T - intracellular - viral, parasitic, bacterial

Question 5

Describe the clonal selection hypothesis and give the 2 types of cells that result

Answer 5

• B cell with specific antibody that binds the specific antigen differentiates into MANY plasma cells
• these plasma cells all produce the same Ab
• B cells can also differentiate into memory cells - that do not currently poruce Abs unless 2ndry infection occurs

Question 6

Antibodies may be ____ of infections

Answer 6

diagnostic

Question 7

What is an antigen?

Answer 7

molecule (protein, carb) that binds antibodies

specific Ab binds an ANT

Question 8

Draw a schematic of an Ab and label it

Answer 8

dont forget the hinge region

Question 9

What does Fc/Fab stand for and state what they bind

Answer 9

• Fc - Fragment crystallisable - binds Fc receptors & complement
• Fab - fragment antigen binding - binds antigen

Question 10

Describe the V and C regions

Answer 10

• encoded for by different exons
• V - bind different atigens
• C - constant for a given Ab H chain / L chain type

Question 11

How can different Ab specificities arise?

Answer 11

multiple V region exons can recombine to give different specifciites

Question 12

Describe IgG/M/A/D/E

Answer 12

• IgG - 2ndry responses, main Ab in serum and tissues
• IgM - 1ry responses
• IgA - important in secretions & protecting mucosal surfaces
• IgD - ?
• IgE - allergy and large parasites , few

Question 13

Give the 2 additional types of Ab L chains and state why they are special

Answer 13

• kappa (K) and lamda
• can belong to different classes eg IgGK (ie aren’t class restricted)

Question 14

Draw a graph that illustrates the 1ry/2ndry response

Answer 14

Question 15

What is classs switching?

Answer 15

• as V and C regions encoded by separate exons, allows the V regions to recombine to gene regions next to diffeent C regions
• this means that same V region, that used to be on IgM Abs, can now exist on IgG therefore has a different effector function

Question 16

Describe afinity maturation

Answer 16

• somatic hypermutation can occur in the V regions leading to a higher binding affinity for the antigen
• almost like natural secletion
• this mutation is selected for

Question 17

Describe the GENERIC effects of immunoglobuilin on pathogens

Answer 17

• bind to and reduce nutrient uptake
• neutralise toxin eg Diptheria
• bind to and prevent adhesion to other surfaces
• promote agglutination of bacteria - easier for phagocytosis

Question 18

Describe the effects of immunoglobulin on pathogens that RELY ON FC REGION

Answer 18

• induce phagocytosis by phagocytes with Fc receptors
• complement activation leading to cell lysis
• enhanced killing by NK cells (ADCC)

Question 20

Which complement molecule is activated when it binds to the Fc region of 2 Abs and what does this lead to?

Answer 20

C1q - leads to inflammation (phagocytes etc) , opsonisation and cell lysis

Question 21

What is the protein that prevents host cells being susceptible to MAC by C9?

Answer 21

CD59 - prevents assembly og the last componenet in MAC formation (C9)

Question 22

Give an example of a bacterial protein that binds the Fc region of IgG and what does this do?

Answer 22

• Staph aureus
• protein A binds Fc region
• prevents phagocytes binding to Fc region of bound IgG antibodies therefore prevents opsonisation

Question 23

What is ADCC and describe it

Answer 23

• antibody dependent cell mediated cytoxicity
• Abs mediate ADCC of NK cells
• NK cells have IgG receptors binding to IgG on bacterial cells stimulates perforin release to punch holes in cell wall and allow contents of granules to be secreted in and induce apoptosis