Chapter 16 videos Flashcards
What is adaptive immune system
- Defenses against specific pathogen Specific Acquired
- Third line of defense
Innate vs Adaptive (Distribution)
Innate
Almost all multicellular eukaryotes
Adaptive
Only in vertebrates
Innate vs Adaptive (Targets)
Innate
Limited number of key structures present in many microbes (PAMPs), perhaps 20-50
Adaptive
Antigens, which are mostly proteins; different ones number in the billions
Innate vs Adaptive (Immune Receptors)
Innate
Pattern recognition receptors, such as Tolllike receptors (TLRs)
Adaptive
T cell receptors and antibodies
Innate vs Adaptive (Cellular Presence)
Innate
Almost all cells
Adaptive
Lymphocytes only
Innate vs Adaptive (Discrimination)
Innate
Host cells do not contain PAMPs
Adaptive
Tolerance for self-antigens can break down, resulting in autoimmune disease
Innate vs Adaptive (Immunological
Memory)
Innate
Absent
Adaptive
Present
What are Five attributes of adaptive immunity?
- Specificity
acts against only one particular antigen - Inducibility (activated because exposure)
- Clonality
proliferate to form many generations of nearly identical cells - Unresponsiveness to self
adaptive immune responses are self-tolerant - Memory
it adapts to respond faster and more effectively
What are two types of lymphocytes?
- B cells
- T cells
Role of B cells
- antibody immune responses (humoral immunity)
- Control of extracellular pathogens and toxins
(free circulating antigens)
Role of T cells
- cell-mediated immune response (cell-mediated immunity)
- Control of intracellular pathogens and stimulates macrophages
What type of pathogen do B cells control?
Free cicurlating Pathogens
What do T cell in charge of?
Remove any intracellular pathogen
Steps in humoral system
- A B cell binds to the antigen for which it is specific. A T-dependent B cell requires cooperation with a T helper (Th) cell.
- The B cell, often with stimulation by cytokines from a Tu cell, differentiates into a plasma cell. Some B cells become memory cells.
- Plasma cells proliferate and produce antibodies against the antigen.
Steps in cell mediated immune system
- A T cell binds to MHC-antigen
comolexes on the surface of the infected cell,
activating the T cell (with its cytokine receptors).
2.Activation of macrophage
(enhanced phagocytic activity). - The CD8T cell becomes a cytotoxic T Lympocyte (CTL) able to induce apoptosis of the target cell.
Adaptive immunity has characteristics that distinguish it from innate immunity, one of which is inducibility. What is inducibility?
A. When there is a virus that can infect both animals and humans
B. When pathogens activate adaptive immunity
C. When a virus cannot cause disease in a particular human because that individual lacks the specific receptor that the virus glycoprotein binds to
D. When adaptive immunity responds only to a specific pathogen
B. When pathogens activate adaptive immunity
What are the targets of the two basic divisions of adaptive immunity?
A. B cells target mainly bone marrow pathogens, and T cells target mainly thymus pathogens.
B. B cells generally target free-floating antigen, while T cells target infected cells.
C. B cells are part of an innate immune response, while T cells are part of an adaptive immune response.
D. B cells target bacteria, while T cells target viruses.
B. B cells generally target free-floating antigen, while T cells target infected cells.
How T cell recptors work?
- T cells act primarily against cells that harbor intracellular pathogens
Specificity of the T cell receptor (TCR): - TCRs do not recognize epitopes (antigens) directly
- bind only epitopes (antigens) associated with an MHC protein
- Only one antigen binding site
How B cell recptors work?
- Major function is the secretion of antibodies
- Specificity of the B cell receptor (BR):
- BCR is a type of immunoglobulin
- BCR can recognize epitopes (antigen) directly
- Two identical antigen recognition site (recognizes only one antigen)
- Bind directly to antigens
B cells vs. T cells (Site of Maturation)
B Cells
Bone marrow
T Cells
Thymus
B cells vs. T cells (Specific Surface
Markers)
B Cells
Immunoglobulin
Several CD molecules
T Cells
T-cell receptor
Several CD molecules
B cells vs. T cells (Circulation in Blood)
B Cells
Low numbers
T Cells
High numbers
B cells vs. T cells (Receptors for Antigen)
B Cells
B-cell receptor (immunoglobulin)
T Cells
T-cell receptor
B cells vs. T cells (Require Antigen
Presented with MHC)
B Cells
No
T Cells
Yes
B cells vs. T cells (Product of Antigenic Stimulation)
B Cells
Plasma cells and memory cellss
T Cells
Several types of sensitized
T cells and memory cells
B cells vs. T cells (General
Functions)
B Cells
Production of antibodies to inactivate, neutralize, target antigens
T Cells
Cells function in helping other immune cells, suppressing, killing abnormal cells; hypersensitivity; synthesize cytokines
What are antigen presenting cell?
Antigens (Ag)
* Molecules that the body recognizes as foreign and worthy of attack
* provoke a specific immune response.
* Recognized by three-dimensional regions called epitopes on antigens
Examples:
* bacterial components as well as proteins of viruses, fungi, and protozoa
* food and dust can also contain antigenic particles
What are Exogenous antigens?
- Originate from microbes outside the body’s cells
- Toxins, secretions and cellular components of microbial cells (membranes, flagella, pili)
What are Endogenous antigens?
Produced by intracellular microbes and are incorporated into the host cell membrane
What are Autoantigens?
- Are components of normal body cells or self antigens
- Self-tolerance Adaptive immunity does not act against normal body cells
(Self-cells)
How Self-tolerance works?
Clonal deletion
* Vital that immune responses not be directed against autoantigens
* To prevent autoimmune diseases
* Body eliminates self-reactive lymphocytes by clonal deletion
* Lymphocytes that react to autoantigens undergo apoptosis (programmed cell suicide) and deleted from the repertoire of lymphocytes
How does Clonal deletion of T cells?
- In the thymus each lymphocyte randomly gets a TCR
- their TCRs should be complementary to the body’s MHC proteins
- if no, they undergo apoptosis; clonal deletion T cells should not recognize self antigens
- If yes, they they undergo apoptosis; clonal deletion
Some “self-recognizing” T cells become regulatory T cells - T cells that recognize M H C protein and foreign epitopes become repertoire of protective T cells
T cells mature in the thymus. Which T cells are deleted by apoptosis during the maturation process?
A. T cells that bind to both MHC Il and to autoantigens
B. T cells that bind to both MHC I and autoantigens
C. T cells that bind to MHC I and exogenous antigens
D. T cells that bind to MHC I and do not bind to autoantigens
T cells that bind to both MHC I and autoantigens
How does Clonal deletion of B cells?
- Cells whose BCR is
complementary to autoantigen will undergo apoptosis; clonal deletion - Occurs in the bone marrow
What does Lack of self-tolerance leads to?
autoimmune disorders
Types
-respiratory system
-Gastrointestinal and Pancreatic
-Systemic/Blood
- endocrine system
- Kidneys
- Connective Tissue
(Bone, Joints, and Skin)
-Neuromuscular
Who presents the antigen to T cells?
Antigen-Presenting Cells (APCs)
* B cells, Macrophages and Dendritic cells
APCs Characteristics:
* They all have Major Histocompatibility Complex (MHC)
MCH characteristics:
* Are glycoproteins (receptors) found in the membranes of most cells of vertebrate animals
* Hold and position antigenic epitopes for presentation to immune cells (T cells)
* Important in determining compatibility of tissues for tissue grafting
What are The two classes of MHC proteins.
- Class I MHC on every nucleated
Cell except red blood cells - Class II MHC on B cell or other antigen presenting cell (APC), (macrophages, B cells, dendritic cells)
The processing of endogeneous antigens.
The processing of exogenous Antigen
Steps involved in activation of cytotoxic T cells
- Antigen presentation
- Helper T cell differentiation
- Clonal expansion
- Self-stimulation
T cells are activated by antigen-presenting cells in lymphatic tissues
Activated T cells undergo proliferation and differentiation
Various TH subclasses : Functions: Activate B cells, T cytotoxic cells, macro-phages, and other white blood cells
Memory Th and Memory Tc : Functions: Long-lived cells that remain in lymphatic tissues; quickly mount immune response upon re-exposure
Various To subclasses : Functions: Seek and destroy cells infected with intracellular pathogens and cancer cells;
activate macropnages
T Helper Cells (TH)
T cytotoxic cell: Activated T cytotoxic cells destroy infected cells, cancer cells, and transplanted tissues.
T helper cell: Activated T helper cells release cytokines that can stimulate or suppress other white blood cells.
B cell : B cells are stimulated by T helper cells. Activated B cells (plasma cells) will secrete antibodies.
Three examples of T helper cell subclasses
T helper 1 cells : Stimulate –> T cytotoxic cells –> Cellular response promoted
T helper 2 cells: Stimulate –> B cells –> Humoral response promoted
T regulatory cells: Decrease immune response once the threat has passed
The effects of the binding of a T-independent antigen by a B cell.
A T-dependent antibody immune response. Steps
- APC presents
antigen to Th cells for Th activation and cloning.
2.Th cell differentiates into T2 cell.
3.Th2 cell activates B cell.
4.memory b cells
Antibody Structure and Isotopes
- The tips of the molecule are the antigen-binding sites
- Antibodies consist of heavy and light protein chains that are connected by disulfide bridges.
All the antibodies made by a given plasma cell will recognize the exact same epitope.
Six functions of antibodies.
1.Neutralization : They stick to antigens and block their attachment sites Stops pathogens from entering the host cells
2.Opsonization: They bind to the surface of immunogens and the Fc region interacts with the phagocytes (“calls” them to the site of infection
3.Oxidation: Antibody pathogen complex oxidizes pathogen
- Agglutination: They clump particles together so phagocytosis can occur more efficiently
5.Antibody-dependent cellular cytotoxicity (ADCC): The heaby chain region of the antibody interacts with eosinophils which release enzymes and reactive oxygen species to attack parasites
- Activation of complement and inflammation: When antibodies activate a protein that assists in membrane perforation (membrane attack complex)
Classes of antibodies
IgM - first antibody produced in early infection
IgG - most common and longest-lasting
antibody; crosses placenta
IgA - associated with body secretions
IgE - involved in response to parasitic infections and allergies
IgD - bound to B; exact function is not
Immunological memory Graph Primary response vs Secondary response
Secondary exposure to the same antigen is rapid and effective
Frequently will not experience disease symptoms while our bodies eliminate the pathogen
