Specific Immune Defenses Flashcards
What are Specific Immune Defenses also referred to as?
Adaptive Immune Responses
What does specificity mean?
response vs individual antigens
What does diversity mean?
response vs many antigens
What does Inducibility mean?
Specific defenses are only turned “on” when needed
What does Clonality mean?
Specific Response makes many cells with the same antigen specificity (either B or T cells)
What does Tolerance mean?
Specific responses are programed to ignore self antigens because some are anti-you
What would happen if your immune system didn’t ignore self antigens that were anti-you?
you would have an autoimmune response and your cells and tissues would kill you
What does it mean when we say Specific Responses have “Memory”
Cells from 1st response vs antigen rapidly respond to later exposure to the same antigen
True or False:
Polypeptide antigens are the weakest antigens
False, they are the strongest
What constitutes an antigen?
-foreign molecule
-non-self
-located on surface of an organism/secreted by an exotoxin
-antibodies are attached
What are the Specific Immune Responses?
Cell-Mediated Immunity
Humoral Immunity
What is Cell-Mediated Immunity?
-T cells and T cell receptors
-Results in secretion of cytokines and/or cytotoxins (Th cells perform this)
-They target infected cells (w/ intracellular microbes), larger microbes, and cancer cells
What is Humoral Immunity?
-B cells and B cell Receptors
-Results in production of antigen specific antibodies (can function as antigen presenting cells)
-They target small, extracellular agents: extracellular bacteria, toxins, extracellular viruses
What are the properties of T cells?
-TCR is membrane bound
-peptides only in context of MHC on APC or abnormal cell
-Includes Th and Tc (cytotoxic)
-Secretes cytokines or cytotoxins
-Has CD4 (Th and Tm) or CD8 (cytotoxic T cells) as surface markers
-Proliferate and Differentiate when Ag-activated
-requires co-stimulation
What are the properties of B cells?
-BCR is membrane bound Ig (Igs can be secreted too)
-can recognize antigen alone AND non-peptide antigens
-There are a subset of B cells not different in function
-Secretes Ig as Antibody and Cytokines
-Ig acts as surface marker
-Proliferate and then become plasma cells when activated
-Do not require co-stimulation but the response is best if it happens
Where are antigen-specific B and T cells activated?
In the Lymphoidal tissues upon exposure to the antigen
What needs to be presented to T cells in order to be stimulated?
Antigen must be presented to T cell with an MHC protein
What can B cells be stimulated by?
-T independent stimulation
-T dependent stimulation
What is T-independent stimulation?
B cells directly binds antigen with its BCR and is stimulation without T cell help (B cell is not fully stimulated)
What is T-dependent stimulation?
Antigen-specific T cell helps activate B cell fully. Makes all classes of antibodies and cause B cells to divide and create memory cells
*ENABLES CLASS SHIFTING AND MEMORY RESPONSE
How are T cells differentiated?
By cytokine secreting types
-Th1 promoted cell mediated immunity
-Th2 promotes humoral immunity (secretes cytokines for B cells)
*Both Th1, Th2, and Tm, are considered CD4+
(Tc cells are considered CD8+)
True or False:
T cells recognize ONLY presented peptide antigens
True
Why is T cell activation controlled by a 3 signal model?
You will not have regulation of your immune system otherwise
True or False:
Threshold binding is not a form of regulation
False, threshold binding IS a form of regulation
What is Signal 1 of the “3 Signal Model” for T cell activation
TCR binding of presented antigen at threshold, plus
-CD4+ T cell and antigen MHC-II on an APC(antigen presenting cell)
OR
-CD4+ T cell and antigen MHC-I on an abnormal/infected cell
What is Signal 2 of the “3 Signal Model” for T cell activation
Co-stimulation using other membrane proteins
What is Signal 3 of the “3 Signal Model” for T cell activation
APC and T cell “cytokine help”
True or False:
T cells are potentially dangerous and you do not want to inactivate them inappropriately
True
True or False:
T cells are potentially dangerous and you do not want to inactivate them inappropriately
True
True or False:
The Humoral Immune Response features the production of ANTIGENS
False, the Humoral Immune Response features the production of ANTIBODIES
What occurs in genes for Antibody Heavy Chains and Light Chains?
Recombination
Where/when does the recombination of genes occur for antibodies heavy and light chains?
-occurs in bone marrow
-occurs before B and T cella are exposed to the antigen
What is the result of “different” antigen-specific B cells
-Delete the anti-self clones
-leads to immune response tolerance of you
-Anti-antigen clones are left and can be selected
Can antibodies switch classes of antibodies without changing its antigen specificity?
YES
What is Signal 1 of the “3 Signal Model” for B cell activation
BCR binding of antigen at threshold level
What is Signal 2 of the “3 Signal Model” for B cell activation
-T-independent = lower response
-T-dependent = co stimulation using membrane proteins (promotes Ig class shifting and B memory cells)
What is Signal 3 of the “3 Signal Model” for B cell activation
Cytokine help (2-way)
Immunoglobulin class switching can lead to what?
Increased antibody affinity (attraction between antigen and antibody) for the antigen
What is IgM and what does it do?
-Activates complement
-First Antibody
-B cell receptor
What is IgD?
B cell receptor
What is IgG and what does it do?
-placental transfer
-binds phagocytic cell surfaces
-activates complement
-Involved in opsonization and ADCC
What is IgE and what does it do?
-Binds mast cell surfaces
-Involved in allergic responses
What is IgA and what does it do?
Two subclasses:
-IgA1
-IgA2
*found as dimers in secretions
What is the order for Antibody-mediated immune reactions?
Neutralization, Opsonization, activate complement, ADCC
What is a live attenuated vaccine?
-Live microbe, but microbe can’t cause disease
-Longer duration/more effective –> “full” immune response
-Risk of reversion to virulence
What is a killed vaccine?
-Dead microbe/inactivated virus
-Shorter duration –> “incomplete” immune response
-No risk of reversion
What are toxoid vaccines?
they contain inactivated exotoxins
What re subunit vaccines?
they are made with antigenic part of the microbe
What are cytokines?
-proteins secreted for communication
-NOT antigen specific
-must be stimulated by the immune system
-have to be produced and secreted from scratch
-only secreted when needed
-diffuse out to neighboring cells (short: distance, time and low conc.)
-bind to specific membrane receptors, signal the receiving cell to alter its gene expression
Can act on cells that secreted them or nearby cells
