B Cells and antibody production

Question 1

What do the immune and adaptive immune processes depend on?

Answer 1

Blood cells- produced in the marrow of our long bones from stem cell precursors. These blood cells perform immune functions.

Question 2

What are the blood cells produced by these stem cells called?

Answer 2

Megakaryocyte

Question 3

What other cells are produced from megakaryocyte?

Answer 3

1. Platelets-clotting factors
2. B cell and T-cell
3. Eosinophil
4. Monocyte= macrophage
5. Basophil
6. Neutrophil
7. Red cell

Question 4

What are the two primary lymphoid organs?

Answer 4

1, Bone marrow

2. Thymus

Question 5

What do primary lymphoid organs do?

Answer 5

Makes lymphocytes

1. Bone marrow- B lymphocytes
2. Thymus- T lymphocytes

Question 6

What are the secondary lymphoid organs called?

Answer 6

Spleen, lymph nodes, tonsils, adenoids, Peyer’s patches, Skin

Question 7

What do the secondary lymphoid organs do?

Answer 7

Lymphocytes in the primary lymphoid organs migrate here

• Filter foreign matter out of the body fluids
• Carry out immune responses to foreign antigens.

Question 8

How are primary and secondary lymphoid organs connected together and to the rest of the body’s tissues?

Answer 8

By blood and lymphatic vessels, through which fluids and cells are constantly flowing.

Question 9

How much of the total body lymphocytes are circulating at any one time?

Answer 9

10%

Question 10

What is the circulatory pathway of lymphocytes?

Answer 10

1. Lymphocytes leave the bloodstream, squeezing through capillaries called high endothelial venules(HEV), and entering tissues such as lymph nodes.
2. They accumulate in small lymphatic vessels that connect to a series of lymph nodes downstream.
3. Passing through larger and larger vessels the lymphocytes enter the main lymphatic vessel- thoracic duct which carries them back into the blood.

Question 11

What is the purpose of continuous recirculation of lymphocytes?

Answer 11

Ensures that the appropriate lymphocytes will come into contact with antigen and with each other to disperse the activated lymphocyte cells throughout the body’s tissues.

Question 12

What are the two subpopulations of lymphocytes?

Answer 12

1. Effector

2. Regulator

Question 13

What are the are the effector and regulator subpopulations responsible for?

Answer 13

Effector- Recognizing, responding to and disposing of antigenic substances.
2. Primarily involved in controlling of the effector functions.

Question 14

What are the effector responses and the lymphocytes responsible for it?

Answer 14

1. Antibody production(B lymphocytes)= main one
2. Antigen specific cytotoxicity (CD8 T lymphocytes)= main one
3. ADCC- Antibody dependent cell mediated cytotoxicity(K cells)
4. Natural killer cells activity( NK cells)

Question 15

What are regulatory responses and the lymphocytes responsible?

Answer 15

1. Cytokine production( CD4 lymphocytes)
2. Helper cells(TH1- viruses, bacteria and TH2-parasites, allergies)
3. Treg- downregulation of responses.

Question 16

What is a primary immune response?

Answer 16

1. Occurs when an antigen is present, which has not been previously encountered by the adaptive immune system.
2. There is a lag period of a few days before effectors(antibodies or cytotoxic T lymphocytes) specific for that antigen appear in the blood.
3. These effectors can bind to antigens and lead to their neutralisation or removal.

Question 17

What is called a secondary response?

Answer 17

If we are exposed to the same antigen that has been dealt with before by the immune system, then the response is much more rapid and vigorous than the primary response. This is due to immunological memory.

Question 18

What are antibodies or immunoglobulins made of?

Answer 18

> Four polypeptide chains held together by disulphide bonds and non-covalent interactions.
2 heavy and 2 light chains in a covalently bonded structure with globular domains and variable and constant regions.

Question 19

How do B cells generate an antibody response?

Answer 19

1. Antigens select and bind to antigen-sensitive B lymphocytes that have surface immunoglobulin receptors with appropriate affinity.
2. Helper T cells provide these virgin B lymphocytes with further activation signals
3. Activation of these B lymphocytes results in proliferation of plasma cells which secrete soluble antibodies of the same antigen-binding specificity as was present on the surface immunoglobulin of B cell.
4. A population of memory cells is also produced as a result of this clonal activation and expansion process.

Question 20

Why are memory cells useful?

Answer 20

> Produce more rapid and larger responses.
more long-lived than precursor B cells
replace the B cells
Don’t need helper cells to identify danger
make memory cells in case the antigen comes back-the immune system can recognise it.
they circulate so the memory of the antigen goes to other organs.

Question 21

How do antibodies work within the body?

Answer 21

1. Direct neutralisation
2. Complement activation
3. Opsonisation
4. Antibody-dependent cell mediated cytotoxicity.

Question 22

How does direct neutralisation work?

Answer 22

Antiviral antibodies prevent virus adsorption

Question 23

How does complement activation work?

Answer 23

> Antigen bound to antibody(antigen-antibody complex) activates the complement system
The complement system is a series of proteins that act in an enzymatic cascade.
Activation of the complement system is important in destroying foreign material due to
: Chemotaxis- Attraction of phagocytic cells to the site of complement activation(where bacteria are)
: Opsonisation- Enhancement of the phagocytic process.
:Lysis- Destruction of cell membranes

Question 24

How does opsonisation work?

Answer 24

Phagocytic cells possess cell surface receptors for the Fc region of antibody molecules
> therefore the antigen cannot bind directly to these but the use of these receptors is to bind with high affinity to the antibody carrying the antigen.

Question 25

How does antibody-dependent cell-mediated cytotoxicity occur?

Answer 25

Through K cells.
K cells have Fc receptors so they can bind the antibody to itself-the antibody has the foreign material attached to it.
> K cells are not phagocytic but they are able to kill the cellular material(bacteria) which they become bound to through the antibody. They kill them by releasing short range cytotoxicity factors.