Lecture 13: Adaptive Immunity Flashcards
What is specific immunity?
aka the third line of defense or adaptive immunity
the body’s ability to recognize and defend itself against distinct invaders and their products
A “smart” system whose “memory” allows it to respond rapidly to a second encounter with a pathogen
What are the types of specific immunity?
Humoral: antibodies produced by B cells
Cell-mediated: involves T cells
What is an antigen (Ag)?
a substance that causes the body to produce specific antibodies or sensitizes T cells (from the invaders)
What is an antibody (Ab)?
A protein made in response to an antigen (from the hosts)
What is the overview of adaptive immunity?
- lymphocyte development and differentiation
- the presentation of antigens
- the challenge of B and T lymphocytes by antigens
- B-lymphocyte response (the production and activities of antibodies) and T-lymphocyte response (cell-mediated immunity)
What is the lymphatic system?
Screens the tissues for foreign antigens
Composed of lymphatic vessels and lymphatic cells
Lymph system vs blood system
see more
Lymphatic vessels:
Form a one-way system: conducts lymph from local tissues and returns it to the circulatory system
What is lymph?
A liquid:
-similar composition to blood plasma
-arises from fluid leaked from blood vessels into surrounding tissues
Lymphatic cells:
From stem cells in bone marrow
Includes lymphocytes, smallest leukocytes
What are lymph nodes?
Houses leukocytes that recognize and attack foreign antigens present in the lymph
Concentrated in the cervical (neck), inguinal (groin), axillary (armpit), and abdominal regions
Role of spleen as lymphatic organ
Similar in structure and function to the lymph nodes
Filters bacteria, viruses, toxins, and other foreign matter from the blood
Role of tonsils and mucosa-associated lymphoid tissue (MALT)
Physically trap foreign particles and microbes
MALT includes the appendix, lymphoid tissue of the respiratory tract, and Peyer’s patches in the wall of the small intestine
Discuss B lymphocytes
Arise and mature in the red bone marrow
Found primarily in the spleen, lymph nodes, red bone marrow, and Peyer’s patches
Small percentage of B cells circulate in the blood
Major function is the secretion of antibodies
Discuss antibodies
Also called immunoglobulins (Ig)
Soluble, proteinaceous molecules that bind antigen
Secreted by plasma cells which are B cells actively fighting exogenous antigen
Part of the humoral immune response
Discuss T lymphocytes
Produced in the red bone marrow and mature in the thymus
Circulate in lymph and blood to lymph nodes, spleen, and Peyer’s patches
Part of the cell-mediated immune response, act directly against antigens:
-endogenous invaders
-many of the body’s cells that harbor intracellular pathogens
What are the ways that antibodies function?
Activation of complement
Stimulation of inflammation
Agglutination
Neutralization
Opsonization
Antibody-dependent cell-mediated cytotoxicity
Discuss antigens
Molecules that trigger a specific immune response
-components of bacterial cell walls, capsules, pili, and flagella
-proteins of viruses, fungi, and protozoa
Contain antigenic determinants (epitope)
Food and dust can also contain antigenic particles
What are the ways antigens can enter the body?
Through breaks in the skin and mucous membranes
Direct injection, as with a bite or needle
Through organ transplants and skin grafts
Discuss antigenic determinants
Parts of an antigen
Antibodies recognize and react with antigenic determinants or epitopes
Haptens
Small separable parts of an antigen
must specifically bind to an antibody to stimulate antibody production
Which T cell type is mainly responsible for interaction with B cells?
T helper cell 2 (TH2)
T cell type mainly responsible for interaction with B cells:
Drives B-cell proliferation; secretes IL-4, IL-5, IL-13
Which T cell type is mainly responsible for inflammation promotion?
T helper cell 17 (TH17)
Promotes inflammation; secretes IL-17; important in lung immunity
Which T cell type is mainly responsible for cell-mediated pathway?
T helper cell 1 (TH1)
Activates the cell-mediated immunity pathway;
secretes tumor necrosis factor and interferon gamma;
also responsible for delayed hypersensitivity (allergy occurring several hours or days after contact)
Which T cell type is mainly responsible for prevention of autoimmunity?
T regulatory cell (TR)
Controls specific immune response
Prevents autoimmunity
Which T cell type is mainly responsible for foreign cell lysis?
T cytotoxic cell (TC)
Destroys a target foreign cell by lysis
Important in destruction of complex microbes, cancer cells, virus-infected cells
Graft rejection
Requires MHC-1 for activation
What do memory T cells do? How are they formed?
Differentiate after activation of T helper or T cytotoxic cell
Do not participate in initial response but seed immune tissues to be activated in future responses
Always bear receptors for the specific antigen that originally activated TH or TC cell from which they are derived
What are on the surface of B cells and T cells?
B cells:
Immunoglobulin; B-cell receptor; MHC II marker
T cells:
Distinct CD molecules: CD3, CD4/ CD8; T-cell receptor
What are antibodies?
Also called immunoglobulins (Ig)
Soluble, proteinaceous molecules that bind antigen
Secreted by plasma cells, which are B cells actively fighting exogenous antigen
Part of the humoral immune response
Antibody function: Activation of complement:
The interaction of an antibody with complement can result in the specific rupturing of cells and some viruses
Antibody function: Agglutination
The capacity of antibodies to aggregate, or agglutinate, antigens is the consequence of their cross linking cells or particles into large clumps. Agglutination renders microbes immobile and enhances their phagocytosis.
Antibody function: Neutralization
In neutralization reactions, antibodies fill the surface receptors on a virus or the active site on a microbial enzyme to prevent it from attaching normally
Antibody function: Opsonization
When antibodies bind to microbes, they encourage the uptake of the microbe by phagocytes. Opsonization has been likened to putting handles on a slippery object to provide phagocytes a better grip.
What are the different types of antigens?
Antigenic determinants
Exogenous antigens
Endogenous antigens
Autoantigens
Clonal Deletion:
The process of destroying B and T cells that react to self antigens
Immune Tolerance:
When lymphocytes develop a harmful specificity for self molecules, they are eliminated from the pool of cells
Clonal Selection of B cells:
Bone marrow gives rise to B cells
Mature B cells migrate to lymphoid organs
A mature B cells recognizes epitopes by B-cell receptors
What are the requirements for effective vaccines? If one requirement is not met, should the vaccine be used? Why or why not?
It should have a low level of adverse side effects or toxicity and not cause serious harm
It should protect against exposure to natural, wild forms of pathogen
It should stimulate both antibody (B-cell) response and cell-mediated (T-cell) response
It should have long-term, lasting effects (produce memory)
It should not require numerous doses or boosters
It should be inexpensive, have a relatively long shelf life, and be easy to administer.
Advantages and disadvantages of live, attenuated vaccines?
Advantages:
Viable organisms can multiply and produce infection but not disease
Confer long-lasting protection
Require fewer disease and boosters
Effective at inducing cell-mediated immunity
Disadvantages:
Require storage facilities
Can be transmitted to other people
Can mutate to become virulent again
How are DNA vaccines made?
DNA that codes for protein antigen is extracted from pathogen genome
Genomic DNA is inserted into plasmid vector; plasmid is amplified and prepared as vaccine
DNA vaccine is injected into subject
Cells of subject accept plasmid with pathogen’s DNA, DNA is transcribed and translated into various proteins
Foreign protein of pathogen is inserted into cell membrane, where it will stimulate immune response.
