The Immune System-Molecular Biology

Question 1

What are Antigens?

Answer 1

Any substance capable of eliciting an immune response

Question 2

Name the 2 broad classes of immune responses

Answer 2

1. Cell Mediated immune response (T Cells)

2. Humoral or Antibody immune response (B cells)

Question 3

What are antibodies?

Answer 3

Antibodies are proteins produced by plasma cells involved in immune response. Antibodies are also referred to as immunoglobulins (Ig)

Question 4

What is Complement?

Answer 4

A collection of blood proteins involved in killing microbes

Question 5

What are Lymphocytes?

Answer 5

The class of white blood cells involved in immune response

Question 6

Name the 2 classes of T cells

Answer 6

Cytotoxic T Cells

T Helper cells

Question 7

Name some functions of T helper cells

Answer 7

1. Enhance response of lymphocytes

2. Help B cells in antibody response

Question 8

What are the functions of cytotoxic T cells?

Answer 8

Kill infected cells

Question 9

What are effector cells?

Answer 9

Cytotoxic T cells and B cells are referred to as effector cells because they are involved directly in killing microbes

Question 10

Where do lymphocytes develop from?

Answer 10

Pluripotent hemopoietic stem cells which give rise to all blood cells.

Question 11

Where do T cells mature?

Answer 11

Thymus

Question 12

Where do B cells develop?

Answer 12

Bone marrow

Question 13

Name the primary or central lymphoid organs

Answer 13

Bone marrow, thymus

Question 14

Name the secondary or peripheral lymphoid organs

Answer 14

Lymph nodes, spleen, epithelium associated lymphoid tissues found in GI tract, respiratory tract, and skin

Question 15

Where in the body do T and B cells react with foreign antigens?

Answer 15

Secondary or peripheral lymphoid organs

Question 16

When does it become possible to distinguish between T and B cells?

Answer 16

T and B cells become morphologically distinguishable only after they have been stimulated by antigens.

Question 17

What do activated B cells develop into?

Answer 17

Antibody secreting cells the most mature of which are plasma cells which are filled with an extensive rough endoplasmic reticulum.

Question 18

What do activated T cells do?

Answer 18

Activated T cells unlike B cells have very little rough ER and do not secrete antibodies. They do however secrete a variety of mediators called lymphokines; interleukins (IK) and cytokines

Question 19

T/F The immune system works by clonal expansion.

Answer 19

True

Question 20

T/F The majority of T and B cells continuously recirculate between the blood and secondary lymphoid tissues

Answer 20

True

Question 21

T/F The antigen specific receptors on B cells are antibody molecules

Answer 21

True

Question 22

Describe structure of antibody

Answer 22

1. Y-shaped molecule
2. Has 2 identical antigen binding sites at the tip of each arm of the Y
3. Has flexible hinge region that allows the distance between the 2 antigen binding sites to vary
4. Consists of 4 polypeptide chains
   - 2 identical light (L) chains and 2 identical heavy (H) chains. L chain has ~200 AAs, H chains has ~440 AAs
   - 4 chains are held together by a combination of noncovalent and covalent disulfide bonds

Question 23

Name the 5 classes of antibodies

Answer 23

IgA, IgD, IgE, IgG, and IgM (ADEGM)

Question 24

Name the 5 classes of Heavy (H) chains

Answer 24

alpha, delta, epsilon, gamma, and mu

Question 25

What heavy (H) side chains does each class of antibodies have?

Answer 25

IgA  alpha--dimer
IgD  delta
IgE   epsilon-
IgG   gamma-
IgM  Mu- pentamer

Question 26

Name the first class of antibody to be produces by a developing cell

Answer 26

IgM

Question 27

How many antigen binding sites does IgM has? How many antigens can it bind at the same time?

Answer 27

5 binding sites

10 antigens

Question 28

What are some of the differences between T and B cells?

Answer 28

T Cells
- Act only at short range
- They interact directly with target cell
- Can recognize antigens only when antigen is displayed on surface of target cell
- T cells recognize peptide fragment of protein antigen that have been partially degraded inside target cell
- Antigen receptors made by T cells exist only in the membrane-bound form. They are not secreted.
B Cells
- Secrete antibodies that can act far away
- B cells recognize intact antigens

Question 29

What are T cell Receptor?

Answer 29

They are antibodylike heterodimers

Question 30

Describe the structure of the T cell receptor

Answer 30

Composed of a and b polypeptide chains. Ech chain is about 280 aas. Has an extramolecular part that is folded into 2 Ig-like domains; one variable and the other constant.