Term
Innate (nonspecific) Immunity |
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Definition
•Rapid response to a broad range of microbes
•Not selective
•1st & 2nd lines of defense
•Physical & chemical barriers
•Cellular defense |
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Term
Adaptive (specific) Immunity |
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Definition
- Slow response to specific microbes
- Highly selective
- 3rd line of defense
- Humoral response
- (B cell/antibody mediated)
- Cell-mediated responses
- (T cell mediated)
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Term
Acquired specific immunity |
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Definition
–Acquired only after an immunizing event (infection or vaccine)
–Product of B and T lymphocytes
–Resist the specific pathogen and provide long-term protection against future attacks
–Lymphocytes undergo a selective process that specializes them for reacting to only one specific antigen or immunogen |
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Term
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Definition
- Body’s ability to react with multiple foreign substances |
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Term
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Definition
- Molecules that stimulate a specific immune response by T and B cells
- Protein or polysaccharide molecules on or inside cells and viruses
- Any exposed or released protein or polysaccharide is potentially an antigen
- Usually, our own antigens do not evoke a response from our own immune system
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Term
4 main characteristics of Specific Immunity |
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Definition
1) Diversity of antigen receptors
2) Specificity of antigen receptors (specific antibodies are developed only after exposure to a specific antigen)
3) Self-tolerance of the system (no mature T and B cells that react against self components)
4) Immunological memory (an enhanced response to previously encountered foreign molecule because B and T-memory cells "remember" the antigen and respond very rapidly on subsequent exposures) |
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Term
MHC- Major Histocompatibility Complex |
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Definition
- Involved in recognition of self & nonself
- Not found on RBC
- Allow for recognition of self
- Each human inherits a particular combination of class I MHC genes
- On macrophages, dendritic, B cells
- Involved in presenting antigens to T cells
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Term
CD - Cluster of Differentiation |
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Definition
- Found on the membranes of a variety of different immune cells; over 300 described
- CD3: on all T cells; assist in binding
- CD4: on T helper and T regulatory cells; bind to MHC-II on macrophages
- CD8: on T cytotoxic cells; bind to MHC-I on virally infected, cancer & foreign cells
- CD25: on T regulatory cells |
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Term
Principal stages of immunologic development and interaction |
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Definition
1) Lymphocyte development and differentiation (by clonal deletion)
2) Presentation of antigens (and clonal selection) initiates primary immune response!
3) Challenge of B and T lymphocytes by antigens (and clonal expansion)
4) Lymphocyte response
a) B-cell response: Humoral Immunity (production and activities of antibodies)
b) T-cell response: Cell-mediated immunity |
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Term
Stage I: Development of Lymphocyte Diversity |
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Definition
To be mature = to be immunocompetent (able to react w/foreign substances)
To be naïve = still haven’t gotten in contact w/foreign substance; waiting to be activated by an antigen |
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Term
Origin of Immunologic Diversity |
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Definition
•Stem cells become granulocytes, monocytes, or lymphocytes in the bone marrow
•Lymphocytes become either B or T cells
•For differentiation (maturation)
–B cells stay in the bone marrow
–T cells migrate to the thymus
•After maturation, each naïve lymphocyte bears a unique antigen receptor that recognizes a specific antigen
•Both B and T cells migrate to secondary lymphoid tissues |
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Term
Clonal Deletion vs. Clonal Selection |
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Definition
•Clonal deletion: Removal of any potentially harmful clones that recognize self
•Immune tolerance:
–Tolerance to self
–Some autoimmune diseases are thought to be caused by the loss of immune tolerance, the survival of “forbidden clones,” or failure of other systems |
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Term
Specific Events in T-Cell Maturation |
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Definition
• Markers found on T cells:
–Unique Antigen-specific T-cell receptor
–CD3 markers: surround the T-cell receptor and assist in binding
–CD4 or CD8 co-receptor
•CD4: binds to MHC class II molecules
•CD8: found on cytotoxic T cells and binds MHC class I molecules
• T cells constantly circulate between the lymphatic and general circulatory system
–Migrate to specific T-cell areas of the lymph nodes and spleen
–Estimated that 109 T cells pass between the lymphatic and general circulations per day |
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Term
Specific Events in B-Cell Maturation |
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Definition
•B cells mature in the bone marrow
–Hundreds of millions of distinct B cells develop as the result of gene modification and selection
–Circulate through the blood, “homing” to specific sites in the lymph nodes, spleen, and other tissue where they adhere to specific binding molecules
–Have immunoglobulins as surface receptors |
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Term
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Definition
•Large glycoprotein molecules
•Serve as the antigen receptors of B-cells, and when secreted as antibodies
•Composed of:
−Two heavy (H) chains
−Two light (L) chains
−One light chain is bonded to one heavy chain
−The two heavy chains are bonded to each other with disulfide bonds
−Creates a symmetrical, Y-shaped arrangement |
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Term
The Specific B-Cell Receptor |
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Definition
•Antigen binding sites:
–Pockets at the ends of the forks formed by the light and heavy chains
–Can be highly variable in shape to fit a wide range of antigens
•Variable (V) regions:
–Found in antigen binding sites
–Amino acid position is highly varied from one clone of B lymphocytes to another as the result of genetic reassortment |
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Term
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Definition
•Belong to the same protein family as the B-cell receptor
–Similar to the B cell receptor
–Formed by genetic modification
–Has variable and constant regions
–Inserted into the membrane
–Relatively small
–Never secreted |
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Term
Entrance and Presentation of Antigens |
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Definition
•Tissue dendritic cells:
–Ingest the antigen
–Migrate to the nearest lymphoid organ
–Process and present antigen to T-lymphocytes
•Antigen presenting cells:
–Dendritic cells
–Macrophages
–B cells |
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Term
Step II: Presentation of Antigens |
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Definition
•Antigen (Ag):
–A substance that provokes an immune response in specific lymphocytes
–To be perceived as an antigen or immunogen, a substance must meet certain requirements in foreignness, shape, size, and accessibility
•Antigenicity:
–Property of behaving as an antigen |
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Term
Characteristics of Antigens |
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Definition
•Must be perceived as foreign:
–Whole microbes or their parts
–Cells or substances that arise from other humans, animals, plants, and various molecules
–Molecules of complex composition
•Proteins or protein-containing compounds are more immunogenic than repetitious polymers composed of a single unit
•Chemical categories of antigens:
–Proteins and polypeptides, Lipoproteins, Glycoproteins, Nucleoproteins, Polysaccharides, and lipopolysaccharides |
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Term
Effects of Molecular Shape and Size |
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Definition
•A substance must be large enough to catch the attention of surveillance cells to initiate an immune response
–Molecules with a MW less than 1,000 are seldom complete antigens
–MW of 1,000 – 10,000 are weak antigens
–MW of 100,000 are the most immunogenic |
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Term
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Definition
– A portion of the antigen molecule recognized and responded to by a lymphocyte
– The primary signal that a molecule is foreign |
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Term
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Definition
– Consist only of a determinant group
– Too small by themselves to elicit an immune response
– If linked to a carrier group, the combined molecule develops immunogenicity |
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Term
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Definition
–Cell surface markers that occur in some members of the same species but not in others
–Proteins and other molecules of one person that are antigenic to another
–The basis for an individual’s blood group and major histocompatibility profile
–Responsible for incompatibilities that occur in blood transfusion or organ grafting |
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Term
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Definition
–Bacterial toxins
–Potent stimuli for T cells
•Activate T cells at a rate 100 times greater than ordinary antigens
•Can result in an overwhelming release of cytokines and cell death
–Toxic shock syndrome and certain autoimmune diseases are associated with these antigens |
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Term
Stage III: Lymphocyte Challenge and Clonal Expansion |
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Definition
•B cells and T cells proliferate and differentiate when challenged by antigen
•Clone:
–Proliferation of a particular lymphocyte
–Genetically identical cells, some of which are memory cells |
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Term
Step IV: The T-Cell Response to Antigen |
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Definition
•Cell-mediated immunities:
–Require the direct involvement of T lymphocytes throughout the course of the reaction
–Among the most complex and diverse in the immune system
–Involve several subsets of T cells whose actions are dictated by the APCs that activate
them
–T cells require some type of MHC recognition before they can be activated
–All produce cytokines with a spectrum of biological effects |
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Term
Three main functional types of T cells |
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Definition
- Helper T cells: activate macrophages, assist B-cell processes, and help activate cytotoxic T cells
- Regulatory T cells: control the T-cell response
- Cytotoxic T cells: lead to the destruction of infected host cells and other “foreign” cells |
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Term
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Definition
•Play a central role in regulating immune reactions to antigens
–Including B cells and other T cells
–Involved in activating macrophages
•Directly by receptor contact
•Indirectly by releasing cytokines such as interferon gamma (IFNγ)
•Stimulation of T helper (CD4) cells by antigen/MHC complex differentiates them into:
–T helper 1 (TH1)
–T helper 2 (TH2), or
–T helper 17 (TH17)
–Depends on what type of cytokines the APCs secrete |
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Term
Regulatory T (TR) Cells: Cells That Maintain the Happy Medium |
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Definition
•Regulatory T cells:
–In the TH class – carry CD4 and CD25 markers
–Act to control the inflammatory process
–Prevent autoimmunity
–Make sure the immune response does not inappropriately target normal biota
•Regulatory B cells also regulate the degree of response from T cells
–B cells become activated to become plasma cells by cytokines from activated T cells
–Already activated regulatory B cells can secrete their own cytokines to dampen the T-cell response |
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Term
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Definition
– The capacity of certain T cells to kill a specific target cell |
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Term
Killer T (CD8) activation |
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Definition
–must recognize a foreign peptide complexed with self MHC-I presented to it and mount a direct attack on a target cell
–Perforins:
•Proteins that punch holes in the membranes of target cells
•Causes ions to leak out of target cells
•Creates a passageway for granzymes to enter
–Granzymes:
•Enzymes that attack proteins of target cells
–After attack with perforins and granzymes, the targeted cells go through death by apoptosis |
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Term
Cells targeted by TC cells |
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Definition
–Virally infected cells
–Cancer cells
–Cells from other animals and humans |
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Term
Natural killer (NK) cells |
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Definition
- Lymphocyte related to T cells
–Lack specificity for antigens
–Circulate through spleen, blood, and lungs
–First killer cells to attack cancer cells and virus infected cells in a similar manner to TC cells
–Not considered part of specific cell-mediated immunity because they do not possess antigen receptors
–Recently discovered
–Hybrid type: share properties of both T cells and NK cells
•Display T-cell receptors and NK-cell markers
–Stimulated by glycolipids on foreign cells
–Rapidly produce cytokines, granzymes, and perforins
–Trigger self-destruction in target cells |
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Term
B Cell Response to Antigen |
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Definition
•When activated by antigen, a B cell divides, giving rise to plasma cells
–Each plasma cell has the same reactive profile
–Release antibodies into the tissue and blood
–Attach to the antigen for which they are specific and mark it for destruction or neutralization |
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Term
Principal activity of antibody |
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Definition
–Opsonization (call attention to)
–Agglutination (immobilize)
–Neutralization (prevent attachment) |
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Term
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Definition
–Opsonization: attachment of antibody to foreign cells exposes the Fc fragments to phagocytes
–Certain antibodies have regions on the Fc region for binding complement
–In other cells, binding of Fc causes the release of cytokines
•Example: Fc region of IgE releases histamine from basophils and mast cells |
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Term
Accessory Molecules on Immunoglobulins |
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Definition
•Varying amounts of carbohydrates are attached to the constant regions
•J chain:
–Joins the monomers of IgA and IgM
•Secretory component:
–Helps IgA move across mucous membranes |
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Term
Antibody Production Over Time |
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Definition
•Primary response:
–Occurs with the first exposure to antigen
–Latent period:
•Marked by a lack of antibody production
•Antigen is concentrated in lymphoid tissues
–As plasma cells produce antibodies, serum titer increases to a plateau, and then tapers off to a low level over weeks and months |
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Term
Secondary response or amnesiatic response |
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Definition
–Occurs when the immune system is exposed again to the same immunogen weeks, months, or even years later
–Rate of antibody synthesis, peak titer, and length of antibody response is greatly increased over the primary response |
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Term
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Definition
–The concentration of antibodies in the serum
–Can be measured over time to determine how the immune system reacts to antigen |
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