Adaptive Defenses Study Guide Flashcards
two arms of adaptive immunity + what lymphocytes play a role in each
- humoral/antibody mediated immunity - b cells
- cellular/cell-mediated immunity - t cells
humoral/antibody mediated immunity
- “Antibody Mediated”
- Immunity is provided by antibodies in the body’s fluids - blood and lymph
- Antibodies are produced by lymphocytes but circulate freely
- Antibodies bind to extracellular targets and mark them for destruction by phagocytes
cellular/cell-mediated immunity
- Protection provided by lymphocytes
- The targets are cells infected by pathogens, cancer cells, or cells of foreign grafts
- Lymphocytes attack directly by killing the infected cells or indirectly by releasing chemicals
- Chemicals enhance the inflammatory response or activate macrophages
What type of lymphocyte produces antibodies?
B lymphocytes of the humoral immunity
How do antibodies fight invasion?
Antibodies bind to extracellular targets and mark them for destruction by phagocytes
What kinds of cells are targeted in cell-mediated immunity?
Cells infected by pathogens, cancer cells, or cells of foreign grafts
4 characteristics of adaptive immunity
- It involves *lymphocytes: B-Cells and T-Cells
- It is *specific: recognizes and targets identified pathogens/foreign substances
- is it *systemic: not restricted to the initial infection site
- It has *memory: after priming, it can mount stronger attacks
Antigens
antibody generating – they are large, unfamiliar, complex molecules that are intruders or non-self. They are substances that can mobilize adaptive defenses. Complete antigens have immunogenicity – the ability to stimulate specific lymphocytes to proliferate, and reactivity – the ability to react with activated lymphocytes.
Haptens
trouble some small molecules, incomplete antigens. Ex – chemicals found in poison ivy, animal dander, detergents, cosmetics, household products
Is it possible for antigens to provoke immune responses in more than 1 type of leukocyte? how?
Many antigens have a variety of antigenic determinants (the specific parts of the antigen that are immunogenic) on their surface, so they have the ability to mobilize multiple leukocyte populations and produce multiple types of antibodies
role of an APC
Antigen presenting cell – play auxiliary roles – they do not directly respond to antigens
type of lymphocyte especially reliant on APCs
T cells (lymphocytes) cannot recognize antigens without apcs
5 steps of lymphocyte development
- Origin: Originate in red bone marrow - from what?
- Maturation: Cells are “educated” to develop immunocompetence and self-tolerance
Immunocompetence: ability recognize one specific antigen - once achieved, a unique antigen receptor is displayed on the lymphocyte’s surface
Maturation of B-Cells occurs in Bone Marrow
Maturation of T-Cells occurs in the Thymus - Seeding Secondary Lymphoid Organs: naive but immunocompetent B-Cells and T-Cells migrate to 2ndary lymphoid organs and await encounters with antigen
- Antigen Encounter and Activation: antigen binds to the lymphocyte that has its receptor; that lymphocyte is selected for further development - clonal selection
- Proliferation and Differentiation: once activated, the lymphocyte rapidly proliferates to form an army of cells (“a clone”) just like itself - with the same antigen specificity
Most members of the clone become effectors (infection-fighting) cells, but some will become memory cells
Memory cells will lie in wait for a subsequent encounter with the same antigen
positive selection test in lymphocytes
the maturing lymphocyte must be able to recognize the MHC (inability to do this = apoptosis)
negative selection tests for lymphocytes
the maturing lymphocyte must not recognize self-antigen (recognizing self antigen = apoptosis)
What determines the diversity of our antigen receptors?
Our genes – not the antigens we encounter – determine which specific foreign substances our immune system will be able to recognize and resist; the diversity of receptors on our lymphocytes represents genetically acquired knowledge of the microbes likely to be in our environment
The effector B-Cell is called a __________.
plasma cell
plasma cells
They secrete antibodies that circulate in blood or lymph where they bind to free antigen and mark them for destruction
What becomes of the non-effector B-Cells?
become memory cells – memory cells can mount an almost immediate humoral response when the same antigen is encountered in the future
What are the effector T-Cells?
Cytotoxic t (tc) cells
Helper t (th) cells
Regulatory t (treg) cells
Primary Immune Response
occurs on 1st exposure to antigen
- 3-6 day lag time
- B-cells specific to that antigen proliferate, offspring differentiates into antibody-secreting plasma cells
- Plasma antibody levels peak in about 10 days then decline
Secondary Immune Response
occurs on any subsequent exposure to the same antigen
- Response is faster, more prolonged, and more effective; “priming” has already occurred
- 2-3 day lag time
- Plasma antibody concentrations rise sharply to much higher levels than the primary response
- Plasma antibody concentrations remain high for weeks to months
- Memory cells persist for long periods - can retain capacity to produce powerful humoral responses for life
Active Humoral Immunity
your B-cells encounter antigens and produce antibodies against them
- can be natural or artificial
natural active immunity
you contract a bacterial or viral infection, experience symptoms, and develop antibodies
artificial active immunity
you receive a vaccine to prime your immune system
Passive Humoral Immunity
ready-made antibodies are introduced - B-cells are not challenged, immunological memory does not occur
- can be natural or artificial
Natural Passive Immunity
conferred on a fetus or infant when maternal antibodies cross the placenta or are ingested in breast milk
Artificial Passive Immunity
administration of a donor’s antibodies - can be used to treat Hepatitis A, poisonous snake bites, rabies, and tetanus
What type of immunity is garnered through a vaccine?
Artificial active immunity
What role do booster shots play?
intensify the immune response
What portion of an antibody is responsible for forming antigen-antibody complexes?
Variable regions – antibodies responding to different antigens have different variable regions
defense mechanisms of antibodies
Neutralization
Agglutination
Precipitation
Complement Activation (Lysis)
Neutralization
antibodies block specific sites on pathogens to prevent attachment to tissue cells - phagocytes destroy antigen-antibody complexes
Agglutination
antigen-antibody complexes are cross-linked into large latices
Precipitation
soluble molecules are cross-linked into large lattices that fall out of solution - once settled, soluble molecules are eaten by phagocytes
Complement Activation (Lysis)
several antibodies bind close together on a cellular antigen and complement is activated - membrane attack complexes insert into the antigenic cell’s surface and cell lysis occurs
Why are MHC proteins important?
- Major histocompatibility complex – proteins that help identify a cell as “self”
- Contain a self or foreign antigen
- Only identical twins have the same mhc
- T cells can only recognize antigens that are presented on mhc proteins
- Our self antigens are not antigenic to us, but highly antigenic to others
difference in CD4 and CD8 cells
Cd4 can only bind with mhc II and cd8 can only bind with mhc I
