The Immune System-Molecular Biology Flashcards
What are Antigens?
Any substance capable of eliciting an immune response
Name the 2 broad classes of immune responses
- Cell Mediated immune response (T Cells)
2. Humoral or Antibody immune response (B cells)
What are antibodies?
Antibodies are proteins produced by plasma cells involved in immune response. Antibodies are also referred to as immunoglobulins (Ig)
What is Complement?
A collection of blood proteins involved in killing microbes
What are Lymphocytes?
The class of white blood cells involved in immune response
Name the 2 classes of T cells
Cytotoxic T Cells
T Helper cells
Name some functions of T helper cells
- Enhance response of lymphocytes
2. Help B cells in antibody response
What are the functions of cytotoxic T cells?
Kill infected cells
What are effector cells?
Cytotoxic T cells and B cells are referred to as effector cells because they are involved directly in killing microbes
Where do lymphocytes develop from?
Pluripotent hemopoietic stem cells which give rise to all blood cells.
Where do T cells mature?
Thymus
Where do B cells develop?
Bone marrow
Name the primary or central lymphoid organs
Bone marrow, thymus
Name the secondary or peripheral lymphoid organs
Lymph nodes, spleen, epithelium associated lymphoid tissues found in GI tract, respiratory tract, and skin
Where in the body do T and B cells react with foreign antigens?
Secondary or peripheral lymphoid organs
When does it become possible to distinguish between T and B cells?
T and B cells become morphologically distinguishable only after they have been stimulated by antigens.
What do activated B cells develop into?
Antibody secreting cells the most mature of which are plasma cells which are filled with an extensive rough endoplasmic reticulum.
What do activated T cells do?
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
T/F The immune system works by clonal expansion.
True
T/F The majority of T and B cells continuously recirculate between the blood and secondary lymphoid tissues
True
T/F The antigen specific receptors on B cells are antibody molecules
True
Describe structure of antibody
- Y-shaped molecule
- Has 2 identical antigen binding sites at the tip of each arm of the Y
- Has flexible hinge region that allows the distance between the 2 antigen binding sites to vary
- 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
Name the 5 classes of antibodies
IgA, IgD, IgE, IgG, and IgM (ADEGM)
Name the 5 classes of Heavy (H) chains
alpha, delta, epsilon, gamma, and mu
What heavy (H) side chains does each class of antibodies have?
IgA alpha--dimer IgD delta IgE epsilon- IgG gamma- IgM Mu- pentamer
Name the first class of antibody to be produces by a developing cell
IgM
How many antigen binding sites does IgM has? How many antigens can it bind at the same time?
5 binding sites
10 antigens
What are some of the differences between T and B cells?
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
What are T cell Receptor?
They are antibodylike heterodimers
Describe the structure of the T cell receptor
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.
