Adaptive Immunity Flashcards
Name 4 characteristics of adaptive immunity
- Antigen specificity
- Diversity
- Immunological memory
- Self regonition
What are the 2 types of adaptive immunity?
- Humoral immunity
2. Cell-mediated immunity
How is humoral immunity mediated?
Antibodies
How is cell-mediated immunity mediated?
CD8 and antigen-specific T cells
What is an antigen?
A substance capable of inducing a specific immune response
Describe 5 characteristics of antibodies
- Produced by B-cells and plasma cells
- Can be membrane bound or secreted
- Glycoprotein molecules
- Include light and heavy chains
- Held together by disulphide bonds and non-covalent interactions
What are immunoglobulins?
Glycoprotein molecules which are produced by plasma cells in response to an immunogen (antigen) and which function as antibodies
What are gamma globulins?
Antibodies produced in response to antigen injection
How does Ag adsorbed serum differ from immune serum with regards to its protein composition?
- Albumin is present in relatively similar amounts in both serums
- Alpha-1, Alpha-2 and Beta globulins are present in slightly higher amounts in immune serum
- Gamma globulins are present in much higher volumes in immune serum
Describe the structure of an antibody
- Made up of 2 identical heavy chains and 2 identical light chains
- Light chains connected to heavy chains by Na-S-S bond to create chain which also connects 2 heavy chains
- Viable region is made up of part of the heavy chain and part of the light chain and is found in the Fab section
- Fc section binds to Fc receptors on phagocytic cells
Name 5 types of immunoglobulins
- IgA
- IgD
- IgE
- IgG
- IgM
Which immunoglobulin is considered pentameric (not monomeric)?
IgM
Which 2 immunoglobulins are predominant in serium?
- IgD
2. IgG
Which immunoglobulin is responsible for mucosal immunity?
IgA
Explain which immunoglobulin has low serum levels
IgE as it is bound to Fc receptors of mast cells
What happens to IgM if it is on B cells?
It takes on a monomeric form
What are 4 functions of antibodies?
- Block virus or toxin entry
- Bound by complement to lyse bacteria
- Immobilize and agglutinate bacteria
- Activate extra-cellular killing
How do antibodies activate extra-cellular killing?
Act as opsonins
Which immunoglobulin is the major transporter across the endothelium?
IgA
Which 2 immunoglobulins are the major transporters across the placenta?
- IgG1
2. IgG3
Which 3 immunoglobulins struggle to diffuse into extravascular sites?
- IgM
- IgD
- IgE
Which 3 immunoglobulins struggle to carry out the function of neutralization?
- IgM
- IgD
- IgE
Which 2 immunoglobulins are good at opsonization?
- IgG1
2. IgG3
Which 2 immunoglobulins are good at sensitization for killing by NK cells?
- IgG1
2. IgG3
Which immunoglobulin sensitizes mast cells?
IgE
Which 3 immunoglobulins activate the complement system?
- IgM
- IgG1
- IgG3
Why are IgE the best immunoglobulins at sensitizing mast cells?
Mast cells posses Fc epsilon receptor which has a high affinity for IgE
Describe the two reactions which must occur for the activation of antibody producing cells
- APC + T helper cell = T helper cell activation
- Activated T helper cell + B lymphocyte = B lymphocytes differentiate into plasma cells
Describe the activation of immune cells involved in antibody response (until effector and memory cells are produced)
- APC captures pathogen and degrades it by lysosomes
- Peptides of pathogens become expressed with MHC class II proteins on surface of APC
- T helper cell recognises complex
- Specific T helper cell will be activated
- Produces effector and memory cells
Describe the activation of immune cells involved in antibody response (aftereffector and memory cells are produced)
- Effector cell proliferates as it produced IL-2
- Activated T helper cell interacts with B cell
- Receptor on B cell causes activation of B cell leading to clonal expansion resulting in production of plasma cells and memory B cells
What is necessary to facilitate the binding of T helper cells and complexes displayed on APCs or B cells?
Co-receptor, CD4
What are the 2 primary lymphoid organs?
- Bone marrow
2. Thymus
What are 3 secondary lymphoid organs?
- Lymph nodes
- Spleen
- MALT (mucosa-associated lymphoid tissue)
What are 2 reasons for having secondary lymphoid organs?
- Allows close proximity between microbes, dendritic cells and T lymphocytes so recognition can occur
- Allows activated T lymphocytes to interact with B lymphocytes
What is the major difference between primary and secondary lymph tissues?
Primary lymph tissues is where immune cells originate and mature whereas immune cells simply reside in secondary lymph tissues
Explain the pathogenesis of HIV infection
- Immediately following exposure, HIV is present at high levels in the blood
- Within 2 months the level declines in parallel with antibodies against HIV rising
- After a length of time, the level of the virus can suddenly rise in correlation with decrease of antibodies against HIV
- AIDS develops when killed CD4 cells can no longer be replaced
What is a vaccination?
Practice of artificially inducing immunity
What is the goal of a vaccination?
Make memory T helper cells, memory killer T cells and memory B cells that will protect the vaccinated person against future exposure to pathogen
Name 2 antibodies against HIV
- Anti-p24
2. Anti-gp120
What is cell mediated immunity?
Immune response in which antigen-specific T cells dominate
What is the function of cytotoxic T cells?
Principal defence against obligate intracellular microbes such as viruses and some bacteria which proliferate inside host cells
How do viral-infected cells interact with cytotoxic T cells?
T cell receptor interact with cells expressing foreign antigen fragments associated with MHC class 1 molecules
What is the co-receptor necessary for cytotoxic T cells to interact with viral-infected cells?
CD8
Why does a virus express foreign antigen fragments associated with MHC class 1 molecules?
- Viral infected cells cut virus into peptide fragments which will be associated with MHC class 1 molecules
- Complex is transferred onto the membrane surface of infected cells
How do cytotoxic T cells kill viral-infected cells?
- Interacts with viral-infected cell
- Induces secretion of lytic enzymes by the cytotoxic T cells
- Lytic enzymes kill viral-infected cell
Name 3 disorders of the immune system
- Hypersensitivity reactions
- Autoimmunity
- Immunodeficiencies
What are hypersensitivity reactions?
Over-reaction of adaptive immune system to harmless antigens
What is autoimmunity disease?
Misdirected adaptive immune response resulting from a loss of self-tolerance
What are immunodeficiencies?
Components of immune system either absent or defective
