Lecture 15: B lymphocytes and antibodies

Question 1

What are the four cytokine properties?

Answer 1

Pleiotropic (multiple targets) -> B cell proliferation, Th proliferation, Mast cell activation

Redundant (overlapping action) -> B cell proliferation

Synergistic (Assist one another) -> AB class switch to IgE

Antagonistic (inhibits others) -> Block IL-4- IgE class switch

Question 2

What are the affects of interferon alpha and beta?

Answer 2

• Transient viral resistance in viral infected cells

- Attract natural killer cells

Question 3

What are the innate Interferons?

Answer 3

IFN alpha, beta, gamma

- Inhibit viral infections

Question 4

What are the functions of IL1,6 and TNF-alpha?

Answer 4

• Proinflammatory (Esp. bacterial infections)
• Wound healing and tissue repair (non-infected related trauma)
• > Fibroblast proliferation
• > Bone reabsorption
• > Prostaglandin and collagenase synthesis
• > Neuroendocrine effects

Question 5

What are some adaptive cytokine examples and what do they do?

Answer 5

IL-1
-> T and B cell activation

IL-2
-> T cell proliferation and NK cell activation

IFN-gamma
-> Antiviral, macrophage activation, NK cell activation, MHC upregulation

IL 4,5,6
-> B cell differentiation, antibody class switching

Question 6

What are some chemokines and their functions?

Answer 6

IL8 (Alpha chemokine)
- Neutrophil migration

MCP-1, MIP-1a (Beta chemokine)
- Allergic inflammation

Question 7

What are some heamopoetic chemokines?

Answer 7

G-CSF, M-CSF, GM-CSF
- Lineage specific control

IL3
- Proliferation of many lineages in bone marrow

IL5
- Eosinophil growth and activation (Allergy)

IL7

• Erythroblast and megakaryocyte growth
• B cell ontogeny in bone marrow

Question 8

Describe antibody structure

Answer 8

Insert picture

Question 9

What are antibody classes defined by? what are their heavy and light chain isotypes?

Answer 9

Heavy chain isotypes
- Alpha, delta, gamma, delta, epsilon, mu

Light chain isotypes
- Kappa, lambda

Question 10

Describe antibodies in relation to their levels at birth:

Answer 10

• Mostly maternal IgG in utero, this declines at birth
• At birth Bubba IgG levels increase
• Over time IgM and IgA slowly rise around 6 months

Hence insufficiencies may not present till 10 moths post birth. Also antibodies transferred in breastmilk

Question 11

Describe the role of cytokines in B cell clonal activation:

Answer 11

B cell recognize antigens and Th cells produce cytokines and this causes proliferation and differentiation

Question 12

What are the effects of antibodys?

Answer 12

• Blocking and neutralisation
• Agglutination
• Opsonization
• ADCC (K-lymphocytes)
• Complement activaiton

Question 13

Write some notes on antibody blocking and neutralization:

Answer 13

• Attatchment and entry (virus, parasites etc)
• Main protective effect of secretory IgA
• Toxins
• Immoblising bacterial flagella

Question 14

In agglutination what happens over time?

Answer 14

• Antibodys form cross links and become complex, forming larger immune complex sizes (Under constant antibody concentration)

Question 15

Describe IgG opsonisation:

Answer 15

IgG binds antigen, Phagocytes contain receptors for Fc region of IgG and for C3b complement component.

Because IgG Fc region can also bind C3B

Question 16

What happens in ADCC in relation to K cells?

Answer 16

K cells FcR recognize Ig Fc region and kills them.

Question 17

Whats the relation of Ig and complement activation?

Answer 17

Ab binds bacterium and compliment binds Fc region leading to:

• Lysis
• Opsonisation
• Chemotaxis
• And or anaphylaxis
• C5b, 6, 7, 8, 9 form membrane attack complex.

Question 18

Review compliment classic and alternative pathways and affects

Answer 18

Slide 25

Question 19

Describe the classic and alternative pathway of compliment cascade:

Answer 19

Classic pathway
- Antigen-antibody complexes i.e C1,2,4
OR
Alternative pathway
- Pathogen surface, C3b, Factor B, Factor D

leads to:

C3 convertase and this in turn:
-> splits C3 and C5 into C3a and C5a = Vasodilation, mast cell activation and chemotaxis

It also leads to membrane attack complex formation

Question 20

What are the antibody complexes involved in the secondary response (memory)?

Answer 20

IgG and IgA

IgM is minor

Question 21

Write some notes on IgM:

Answer 21

• Largest, pentamer
• 10% AB pool
• First in primary response
• VERY EFFECTIVE AGGLUTINATOR
• Efficient complement activator b/c shape
• Important against blood-borne disease

Question 22

Write some notes on IgG:

Answer 22

• 70-75% immunoglobulin pool

Good:

• Antitoxin antibody
• Effective barrier against virus infections
• Compliment activator
• Strongly bound by phagocytosed cells = enhanced opsonisation

and

Crosses the placenta

Question 23

Write some notes on IgA:

Answer 23

• Predom class in sero-mucous secretion

- Main role is protection of external body surfaces - Gut, resp and genitourinary tracts

Question 24

Write some notes on IgD:

Answer 24

• Trace amounts in blood and secretions
• Found on the surface of antigen sensitive naive B cells
• Receptors for antigen binding to activate naive B cells.

Question 25

Write some notes on IgE:

Answer 25

• Trace amounts in blood
• Binds strongly to mast cells (differentiated basophils)
• Important in parasitic infections and allergies
• Allergens binding to mast cell associated IgE, activates processes that leads to symptoms of allergy or asthma.