2B - Cells and Antibodies

Question 1

B lymphocytes importance, origin, residence

Answer 1

‣ Make antibodies = humoral immunity (blood)
‣ Originate in the bone marrow
‣ Mature and differentiate in the bone marrow in mammals and in the Bursa of Fabricius in Birds.
‣ Reside in the peripheral lymph nodes

Question 2

Activated B cell transition

Answer 2

• B cells are selected, and self-reactive B cells are eliminated in a process like T-cell selection
‣ Clonal deletion
• Each B-cell is specialized to recognize a certain antigen
◦ After being presented with its specific antigen the specialist B cell in the lymph node becomes activated replicated and makes antibodies
◦ Activated B cells become plasma cells
‣ Expansion of plasma → more production of antibodies
• There is a different B lymphocyte for every different antigen (millions of different B lymphocytes)
◦ A specific B cell recognizes a specific antigen

Question 3

Immunoglobulins

Answer 3

serum glycoproteins produced by plasma cells in response to antigenic challenge

Question 4

Antibodies

Answer 4

◦ Antibodies are immunoglobulins that are specific for a certain antigen

Question 5

FAB

Answer 5

Fab binds to antigen

Question 6

FC

Answer 6

binding site for phagocytes

Question 7

Direct effects of antibodies

Answer 7

Neutralization, agglutination, precipitation

Question 8

Neutralization

Answer 8

inactivation of the antigen and makes the agents binding site unavailable for binding with host cells

Question 9

Agglutination

Answer 9

makes soluble antigens clump together

Question 10

Precipitation

Answer 10

makes soluble antigens fall out of solution

‣ Agg and Prec → easier for phagocytes to dispose

Question 11

Indirect effects of antibodies

Answer 11

Opsoniation, Activation of complement by the antibody, activation of cell mediated response

Question 12

Opsinization steps

Answer 12

Fab site binds to antigen, FC site binds to the phagocytic cell. Phagocytic cell eats the AB-AG complex

Question 13

What happens during activation of cell mediated response

Answer 13

‣ The antibody may bind to antigen on infected cells or large target cells like parasites. This will cause the cell to be destroyed by macrophages, eosinophils and NK cells

Question 14

IgM

Answer 14

the first antibody produced in response to an infection
‣ Largest immunoglobulin
‣ Opsonizes bacteria
‣ Lyses bacteria

Question 15

IgG

Answer 15

the major class of antibody and is responsible for more antibody functions (precipitation, agglutination and complement activation) 
‣ Coats the mucosa 
	• Neutralizes toxins and viruses 
	• Inhibits growth 
	• Lyses bacteria 
	• Opsonization

Question 16

How to tell if an infection is new or old

Answer 16

• Find IgM → new/recent infection

* Find IgG → past infection

Question 17

IgA

Answer 17

the dominant antibody in normal body secretions
‣ Present in tears, sweat, saliva, mucous and milk to provides local protection from inhaled or ingested antigens or those that come into contact with the external body surface
• Block adherence
• Inhibit growth
• Immobilize bacteria
• Neutralize viruses

Question 18

IgE

Answer 18

important in allergic reactions and parasitic infections
‣ Exposure to an allergen causes B-cells to produce IgE → IgE Fc binds to Fc receptor on the cell membrane of mast cells
‣ In a sensitized individual cross linking of the two IgE molecules with the antigen causes degranulation of the mast cell and massive release of histamine and other performed mast cell products

Question 19

Histamine

Answer 19

an example of preformed chemical mediator
◦ The effects are almost immediate but do not last long
◦ Histamine is found in the granules of mast cells and basophils
‣ → increase vascular permeability, vasodilation (hyperemia), pain and itching
‣ effects are almost immediate (w/in 1-2 minutes)
‣ Effects are transient (lasts only 30 min)