23 Overview of the immune system Flashcards
Generated from gene rearrangement. These receptors are specific for one antigen
Somatically generated receptors
non-specific cells of the innate immune response. These receptors recognize families of patterns that are found in certain microorganisms and not in the human body
Pattern recognition receptors
soluble proteins located on cell surfaces. Identify pathogens
Pathogen receptors
o Physical barrier:
First line of defense against microbes.
Skin, musuc, membranes lining the organs (large perimeter)
o Innate immune system:
Second line of defense
Eliminate microorganisms and can prevent infection
If elimination of the infection is impossible, the innate immune system will alert the adaptive immune system of the problem and recruit an adaptive immune response
o Adaptive immune system:
Third line of defense
Specificity, diversity, and memory
Three main lines of defense of the immune system
Kill the microorganism by inducing apoptosis. Uses pattern recognition receptors (non-specific)
NK cells
The main phagocytic cells of the innate immune system
Macrophages and neutrophils
24 hours after the initiation of infection. This branch of the immune system is activated
Adaptive immune response
These cells produce antibodies
B lymphocytes
These cells help coordinate the immune response
T lymphocytes
- Specificity: For molecules shared by groups of related microbes and molecules produced by damaged host cells
- Diversity: Limited, germline encoded
- Memory: none
Innate immunity
- Specificity: specific for any particular pathogen that has been identified (microbial and nonmicrobial antigens)
- Diversity: very large, receptors are produced by somatic recombination of gene segments
- Memory: Yes
Adaptive immunity
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aka granulocytes. These are the neutrophils, basophils, and eosinophils
Polymorphonuclear leukocytes
Most abundant leukocyte in blood. Major function is phagocytosis
Neutrophils
Participate in destruction of pathogens that are too big to be phagocytosed by neutrophils or macrophages. These cells release granules that kill the microorganism
Eosinophils & basophils
Contain IgE receptors. These IgE receptors trigger the allergic response when an allergen is encountered for the second time
Eosinophils, basophils, and mast cells
Neutralize the pathogen, preventing infection. ___ do NOT kill microbes. The ___ do however enable the microbe to be identified by phagocytic and Natural Killer cells for destruction
Antibodies
Orchestrate the immune response. Determine which immune cells will be activated (macrophages, phagocytic cells to induce inflammation, induction of proliferation and differentiation of T cells and B cells)
T helper lymphocytes
Induces apoptosis of an infected cell of the human body that is expressing a microbial antigen. Specific for a particular antigen
Cytotoxic T cell
Regulate the immune response. Mainly by suppressing the immune response
Regulatory T lymphocytes
Mainly performed by B cells (that create antibodies)
Humoral immunity
Mainly performed by T helper cells and cytotoxic T lymphocytes
Cell-mediated immunity
Molecules (antigens) that are able to generate an immune response
Immunogens
1) Foreignness
2) Molecular size: Larger molecules mount a larger immune response than smaller molecules (they are visualized more easily by the immune system)
3) Chemical-structural complexity: Complex structures mount stronger immune responses
4) Dosage, route, and timing of antigen administration: If the antigen comes via a route that is designed to mount an immune response, the response will be higher. Ex: an antigen entering the respiratory tract as supposed to an antigen being injected directly into the bloodstream
5) Antigenic determinants (epitopes)
o Epitopes: Small chemical groups on the antigen molecule that can elicit and react with an antibody. An antigen can have one or more epitopes
o Adjuvants: Not an immunogen. They are chemically unrelated to the immunogen, and are not covalently bound to it. Adjuvants enhance the immune response to an immunogen.
Characteristics of an immunogen
A small molecule that can elicit an immune response only when attached to a large carrier such as a carrier protein. The carrier may be one that also does not elicit an immune response by itself (however, the combination does elicit an immune response. This is because in general, only large molecules, infectious agents, or insoluble foreign matter can elicit an immune response in the body)
• Antibodies that are produced can now react to either the ___ or the carrier protein individually
Hapten
T/F. Over-excited lymphocytes are destroyed in the bone marrow before they can mature and spread to the peripheral lymph nodes. This is b/c an easily excitable lymphocyte is likely to destroy cells of the human body that are not infected
True
Specificity: Ensures that the immune response to a microbe (or nonmicrobial antigen) is targeted to that microbe (or antigen)
Diversity: Enables the immune system to respond to a large variety of antigens
Clonal expansion: Increase in the number of antigen-specific lymphocytes to keep pace with microbes
Memory: Increases the ability to combat repeat infections by the same microbe
• Effector cells and memory cells (longer half-life) are produced when a B cell encounters a pathogen. The secondary immune response is more robust than the primary immune response
Nonreactivity to self: Prevents injury to host during responses to foreign antibodies
• Over-excited lymphocytes are destroyed in the bone marrow before they can mature and spread to the peripheral lymph nodes. This is b/c an easily excitable lymphocyte is likely to destroy cells of the human body that are not infected
Specialization: Generates responses that are optimal for defense against different types of microbes
Contraction and homeostasis: Allows immune system to recover from one response so that it can effectively respond to newly encountered antigens
Cardinal features of the adaptive immune system
are a large and heterogeneous group of secreted proteins produced by many different cell types, mediate and regulate all aspects of innate and adaptive immunity
Cytokines
The organs in which lymphocytes are generated and mature
Primary lymphoid organs
Production and maturation of immune cells occurs here
Bone marrow
Maturation of T cells occurs here
Thymus
The organs in which lymphocytes interact with antigens. Antigens are presented to the lymphocytes from the tissues by circulating antigen presenting cells (macrophages & dendritic cells)
Secondary lymphoid organs
(Primary or secondary lymphoid organs?) Lymph nodes & spleen
Secondary lymphoid organs
Collects lymph (fluid) from the tissues into lymphatic vessels, and recycles the lymph back to the blood
Lymphatic system
) is conferred by a host response to a microbe or microbial antigen, whereas passive immunity is conferred by adaptive transfer of antibodies or T lymphocytes specific for the microbe
o Provides resistence to infection and is specific for microbial antigens
o Only the active immune responses generate memory
o Cell transfers can be done only between genetically identical donor and recipient to avoid rejection of the transferred cells
Active immunity
Dysregulated or uncontrolled, excessive, immune response (can be caused by response to foreign bodies or by response to self-antigen autoimmunity)
Hypersensitivity reactions
