Immunology

Question 1

Definr the antigen?

Answer 1

A foreign protein that can evoke an immune response mediated by B (plasma cells) or T lymphocyte

Question 2

Hapten (incomplete antigen) :

Answer 2

A non-protein foreign substance (e.g drug) that can evoke an immune response by combinig with one of the body proteins (this combination acts as an antigen) .

Question 3

Innate (Natural) immunity :

Answer 3

Always present (innate); doesn't change over the time.
1st line of defense

Question 4

Major components of innaye immunity:

Answer 4

Epithelial barrier of skin, GIT and respiratory tract
Specialized cell type called thr natural killer (NK)
Complement
Cellular components : composed of neutrophils, macrophage, Dendritic & langerhans cells.

Question 5

Adaptive (acquired) immunity

Answer 5

2nd line of defense
More specific (adaptive) and powerful than innate

Question 6

Major components of acquired immunity:

Answer 6

Lymphocytes

Lymphocytes products

Question 7

2 types of adaptive immunity :

Answer 7

Humoral immunity (mediated by antibodies)
Cellular immunity (mediated by T cells)

Question 8

Lymphocytes grow up in primary organs, then travel to secondary organs, searching for antigen:

Answer 8

Primary organs : Thymus and BM

Secondary organ: lymph nodes, spleen, mucosal and cutaneous lymphoid tissues

Question 9

B lymphocytes found in :

Answer 9

Peripheral circulation (10-20% of circulating peripheral lymphocytes)
BM
Peripheral lymphoid tissue
Peyers patches

Question 10

Functions of B cells:

Answer 10

Specific antigen stimulation 》 B lymphocytes form plasma cells 》 secrete specific antibodies directed against the antigen that caused its formation

Question 11

What is the humoral immunity?

Answer 11

Iit is immunity that is dependent on the production of antibodies and their actions.

Question 12

What is an antibody?

Answer 12

It is Y shaped glycoprotein
2 light chains
2 heavy chains
Constant region of heavy chain form the Fc fragment
Variable regions of both chains form the fab fragment

Question 13

T lymphocytes found in :

Answer 13

Peripheral circulation (60-70% of lymphocytes).
Paracortical areas of lymph nodes
Periarteriolar sheaths of spleen.

Question 14

T cell surface molecules :

Answer 14

T cell Receptor (TCR)
CD3 Molecular complex
CD4 molecules
CD8 molecules

Question 15

TCR composed of :

Answer 15

An aplha and beta polypeptide chain, each have a variable (antigen-binding) and a constant region.
TCRs are nomcovalently linked to a cluster of five invariant polypeptide chains, the gamma, delta and epsilon proteins of the CD3 molecular complex and two zeta chains

Question 16

Functions of T Cell Receptor :

Answer 16

TCRs bind to antigens presented by macrophages and langerhans cells.

Question 17

Tupes of T lymphocytes :

Answer 17

1.Helper T cell (CD4+)
Helper inducer T cells
Helper suppressor T cells
2.Suppressor T cells (CD8+)
3.Cytotoxic T cells (CD8+)

Question 18

How to activation of T lymphocytes?

Answer 18

They cannot be activated by free antigens.

They are activated by processed antigens presented to them by macrophages, dendritic & langerhans cells.

Question 19

Nk cells are :

Answer 19

Peripheral blood lymphocytes (10-15%), larger than B and T cells, devoid of cell surface immunoglobulin & TCR.

Question 20

Nk cells contain :

Answer 20

Azurophilic cytoplasmic granules (hence called larger granular lymphocytes LGs)

Question 21

Nk cells are part of :

Answer 21

Natural or innate immunity.

Question 22

Function of Nk cells:

Answer 22

Nk cells lyse tumor cells or virus-infected cells without prior sensitization and thus form first line of defense against neoplastic & virus-infected cells.

Question 23

Why nk cells called Natural killer?

Answer 23

It lyse tumor cells or virus-infected cells without prior sensitization.

Question 24

Nk cells have Fc receptors for IgG:

Answer 24

So they can lyse IgG-coated target cell.