EXAM 4: Adaptive

Question 1

Antigen

Answer 1

A foreign substance that induces an immune response in the body

Question 2

Epitope

Answer 2

The part of an antigen that is recognized by a specific antibody

Question 3

Lymph

Answer 3

A fluid derived from the tissues of the body, resembling blood plasma (contains WBCs) and conveyed to the bloodstream by the lymphatic vessels

Question 4

Cluster of Differentiation

Answer 4

A protocol used for the identification and investigation of cell surface molecules providing targets for immunophenotyping of cells

Question 5

Leukocytes

Answer 5

cells of the immune system involved in defending the body against infectious disease

Question 5

Lymphocytes

Answer 5

A cell of the adaptive immune system

Question 6

Cytokine

Answer 6

Signaling molecules secreted by certain cells of the immune system and have a direct effect on other cells

Question 7

Chemokines

Answer 7

Ability to induce directed chemotaxis in nearby responsive cells

Question 8

Clonal Expansion

Answer 8

An immunological response in which lymphocytes stimulated by an antigen proliferate and amplify the population of relevant cells

Question 8

Cytotoxic

Answer 8

Toxic to living cells

Question 8

Opsonization

Answer 8

The process by which a pathogen is marked for ingestion and destruction by a phagocyte

Question 9

Agglutination

Answer 9

A reaction in which particles suspended in a liquid collect into clumps

Question 10

List and describe the attributes of the adaptive immune response.

Answer 10

Unlike innate immunity, adaptive immunity has resistance to a particular foreign agent (memory), resistance increases with repeated exposure
Traits are: AIDS

• antigenic specificity: has specific responses for specific antigens
• immunological memory: defense gets stronger upon repeated exposure
• diversity: can remember & defend against a wide range of pathogens
• self-nonself recognition: able to differentiate between normal cells/products in body and those of antigens

Question 11

Define antigen and discuss the role of antigens in the immune response

Answer 11

Def: A foreign substance that induces an immune response in the body
- the body recognizes certain molecules worthy of attack
- causes immune system to produce antibodies against it

• Recognized by 3D regions called epitopes
• Include various bacterial components
• Food and dust can also contain antigenic particles

Autoantigens: regular cell presentation on cell membrane

Exogenous antigens: presented on surface of bacterial cell

Endogenous antigens: presented on surface of virally infected host cell

Question 12

List the elements of the of the adaptive immune response, including cells, organs, tissues, signaling molecules and describe their specific roles

Answer 12

Lymphatic system: screens the tissues of the body for foreign antigens
* transitions from innate to adaptive response
ANTIGEN PRESENTATION OCCURS HERE

Lymph:
A fluid derived from the tissues of the body, resembling blood plasma and containing white blood cells, and conveyed to the bloodstream by the lymphatic vessels
* Flow of lymph: a one-way system that conducts lymph from tissues and returns it to the circulatory system

Lymphoid Organs:
Primary: red bone marrow, thymus (mature)
Secondary: lymph nodes, spleen, tonsils, MALT (mucosa associated lymphatic tissue)
Lymphocytes:
Identified by cluster of differentiation (CD)
3 major populations:
1. T lymphocytes:
* arise in bone marrow, mature in thymus
* mature cells are naïve until activated during antigen presentation
* Proliferate into various effector and memory cells
CD8+ cytotoxic T lymphocyte: directly kills virally infected cells and abnormal cells
CD4+ helper T lymphocyte: helps regulate B and T cell activities

2. B cells:
   * arise and mature in RB marrow
   * Job is differentiation into the plasma cells and secretion of antibodies
3. natural killer cells:
   * cytotoxic activity by secreting toxins onto surface of virally infected cells and tumors
   * recognizes low levels of MHC1 & Fc portion of antibodies
   * non-specific

T Cell Receptor
* On T cell cytoplasmic membrane
* Do not recognize epitopes directly- only through association with an MHC protein
* intracellular pathogens

B cell Receptor
* Each B cell generates a single BCR (mult. receptor copies)
* Recognizes only one epitope
* Two variable regions of the BCR form the AntBinding sites
* The entire collection of an individual’s BCRs can recognize millions of different epitopes

Question 13

Discuss antibody structure, including different types, and function

Answer 13

Antibody Structure:
* Composed of Fc Body, 2 heavy chains and 2 light chains (linked by disulfide bonds & chains have constant and variable regions)
* Fc body determines type & function of antibody
* antibodies are immunoglobulins similar to BCRs
* secreted by plasma cells
* Antigen-binding sites are complementary to epitopes

ANTIBODY KILLING:
activation of complement
neutralization
opsonization
oxidation
agglutination
antibody-dependent cellular toxicity ADCC

Classes of Antibodies:
* Since threats to immune system vary, so do antibody capabilities
* Class involved in the immune response depend on antigen type, portal of entry & antibody function needed

5 Classes:
IgM: 1st antibody secreted, pentamer, neutralization/agglutination, can activate complement, can pass placenta
IgA: associated w/ body secretions, dimer, neutralization/agglutination
IgG: most versatile, highest concen. & longest lasting antibody, can activate complement
IgE: allergies, response to parasitic infections
IgD: function unknown

Question 14

Compare and contrast the two classes of MHC molecules

Answer 14

Major Histocompatibility Complex: antigens bind in groove of MHC molecules, hold and position antigenic determinants for presentation to T cells

MHC class I:
* found on all nucleated cells
* self and nonself recognizing
* cells display antigens to CD8+ cytotoxic T lymphocytes
* on surface of nuc. cells
* presents endogenous antigen

MHC class II:
* found on all APCs and B-cells
* non-self recognizing
* works with foreign antigens
* cells display antigens to CD4+ helper T cells
* on surface of activated APCs, requires AP
* presents exogenous antigen

Question 15

Compare and contrast clonal selection and clonal deletion

Answer 15

Clonal deletion: it is vital that immune responses not be directed against autoantigens; body eliminates self-reactive lymphocytes through apoptosis

Clonal selection: antigen presentation by dendritic cells lead to activation of T cells, which causes rapid expansion of Active T cells (some memory T cells created)

Question 16

Describe the process by which different cells of the immune system communicate with each other.

List the receptors and signaling molecules used

Answer 16

Cytokines: Signaling molecules secreted by certain cells of the immune system and have a direct effect on other cells. SOLUBLE REG PROTEINS that act as intercellular signals
* Secreted by various leukocytes
* Cytokine network: complex web of signals among all the cells of the immune system

Cytokines examples:
* interleukins: signal among leukocytes
* chemokines: Ability to induce directed CHEMOTAXIS in nearby responsive cells. CHEMOTACTIC cytokines that signal LEUKOCYTES to move

Receptors used:
- BCRs, TCRs, antigens, etc.

Question 17

Describe the main events in cellular and humoral immune responses

Answer 17

cellular:
* Cell-mediated immunity
* T cells require additional signaling from antigen presenting cells (prompts T cell to respond to the antigen)

4 STEPS to activate T Cell clones:
Antigen presentation
Helper T cell differentiation
Clonal expansion
Self-stimulation

humoral:
* Antibody-mediated immunity

B cells must be activated and differentiated into plasma cells
* Secrete antibody molecules complementary to specific antigen
* Short lived cells
T Independent B cell activation
BCR binds antigen directly, clonal expansion/differentiation
T Dependent B cell activation
BCR binds with antigen on a corresponding TCR

Question 18

Discuss the role of memory cells in the immune response, including the primary and secondary immune response

Answer 18

memory B-cells:
* persist for months or years in the lymphoid tissue
* do not secrete antibodies
* have BCRs complementary to the antigenic determinant that triggered their production
* initiate antibody production if antigen is encountered again

memory T-cells:
* persist for months or years in lymphoid tissues
* some activated T cells become memory T cells
* immediately functional upon subsequent contacts with epitope specific to its TCR

When B and T-cells replicate during the primary immune response, they produce effector cells and long-lived memory cells.

Since both are antigen-specific, when they encounter the antigen again, they can mount a more rapid/effective immune response, this is the secondary immune response

Question 19

Compare and contrast the two types of acquired immunity. Differentiate between active and passive

Answer 19

Acquired immunity: specific immunity acquired during life

naturally: response against antigens encountered in daily life/nature

artificially: response to antigens introduced from a vaccine

draw out chart!
active: immunity developed after exposure to infection/vaccine
natural: Abodies made after exposure to infection
artificial: Abodies made after getting a vaccine

passive: immunity acquired from someone else
natural: Abodies transmitted from mother to baby (milk/placenta)
artificial: Abodies acquired from immune serum medicine

Question 20

Discuss the how the innate and adaptive immune responses work together to fight off infection.

Answer 20

innate acts at first fighting off new pathogens with it’s granulocytes, physical barriers, and chemical barriers.

from the innate immune system dendritic cells pass on the antigen information to the adaptive immune system so that the body is able to prevent infection and illness if the pathogen appears again