Week 1: Specific Acquired Immunity Flashcards
Why does the AIS take 7-10 days to ramp up?
Because the APC needs to find the random B and T lymphocytes that are specific to that antigen
How long does it take to generate memory B cells?
1-5 additional days
What are the two kinds of adaptive immunity?
Humoral Immunity and Cell-mediated immunity
What is humoral immunity?
B cells protecting the extracellular spaces of the body- tissue, blood, secretions- by releasing antibodies
What is cell-mediated immunity?
T cells surveying the surfaces of the body’s cells, looking at cells that have parasites in them
Where do B cells locate to release antibodies forever?
Bone Marrow
What are the two MHC molecules?
MHC I and MHC II
What do MHC I present?
antigens synthesized within the cell
What T cell recognizes MHC I molecules?
CD8+ killer T cells
What do MHC II present?
antigens that are products of phagocytosis
What cells present MHC II molecules?
monocytes/macrophages, dendritic cells, B cells, epithelial cells of the thymus
What cells recognize MHC II molecules?
CD4+ helper T cells
What is the function of MHC II molecules on epithelial cells in the thymus?
To train T cells to not react with self antigens
What are the cytokines that switch from CD4+ T cells to Th1?
IL-12
What are the cytokines that switch from CD4+ T cells to Th2?
IL-4
What are the cytokines that switch from CD4+ T cells to Th17?
IL-6 and IL-23
What are the cytokines that switch from CD4+ T cells to Tfh
IL-6, IL-21
What are the cytokines that switch from CD4+ T cells to Treg
IL-2 and TGF-beta
Where to B and T cells begin production at?
Bone Marrow
Where do T cells become mature cells?
Thymus
Where can mature B and T cells be located at?
blood and lymph nodes
What is the function of lymphokines?
attract and activate monocytes and macrophages
What cluster of differentiation is always found on T cells?
CD3
What are the two most common T cell receptors?
alpha-beta and gamma-delta
What is the T cell receptor coupled with?
CD3 complex
How do alpha-beta TCRs function?
by binding MHC I and II molecules
T/F: gamma-delpha TCRs can bind directly without the use of MHC complexes?
True
What TCR do most intraepithelial lymphocytes have?
gamma-delta CD8+ T cells
What is unique about gamma-delta T cells?
They are CD4- and CD8-
What are the 5 specialized subtypes of T helper cells?
Th1, Th17, Th2, Tfh, Treg
What is the function of Th1 helper cells?
make lymphokine that attract thousand of angry macrophages- usually what is involved in organ rejection
What is the function of Th17 cells? What kinds of diseases are they implicated in?
Main role in inflammation, more powerful than Th1 and protect mucosal barrier; implicated in forms of autoimmunity
What is the function of Th2 cells?
stimulate macrophages to become alternatively activated; function in wall-off pathogens and PROMOTING HEALING
What is the function of T follicular helper cells? (Tfh)
after stimulation by antigen, migrate from T cell areas of lymph nodes into B cell follicles where they help activate B cells to make the Ig subclasses
What is the function of Treg cells?
make cytokines that suppress activation and fxn of Th1, Th17 and Th2 cells, KEEP IMMUNE RESPONSE IN CHECK
What is the function of cytotoxic T cells?
destroy any body cell they ID as bearing a foreign or abnormal antigen on its surface
What are the steps of activation of alpha-beta T cells?
Signal 1: TLR recognition of HLA bound Ag (CD4 with MHC2, CD8 with MHC1). Signal 2: B7 (CD80/86) on APC binds to T cell surface prtn CD28. Other stimulation: APC CD58 binds to Tcell CD2, APC releases IL-1 and T cell releases IL-2
What is it better for a CTL to kill an infected cell than let the virus kill it?
Allowing the virus to kill it would allow it to expand its population after lysis of the cell
How to cytotoxic T cells kill?
FAS ligand interaction- activating caspase and apoptosis in target cell. (2) TNF can induce apoptosis, Perforin is a pore-forming protein, Granzymes induce apoptosis
Describe positive selection of T cells
T cells must recognize MHC I or MHC II molecules in order to be stimulated to mature (self-restricted)
Describe negative selection of T cells
T cells that recognize self-antigens bound to MHC II on the thymus epithelial cells are driven to apoptosis (tolerant to self-antigens
What are the surface receptors of B cells that recognize antigens?
IgD or IgM (monomers)
What cells is CD3 found on and what’s its function?
Th and Tc; Signal transduction element of the T-cell receptor
What cells is CD4 found on and whats its function?
Th; adhesion molecule that binds to MHC2 molecules and signal transduction
What cells is CD8 found on and whats its function?
Tc and possibly NK; adhesion molecule that binds to MHC I molecules and aids in signal transduction
What cells is CD16 (Fc(gamma)RIII) found on and whats its function
NK cells; low-affinity receptor for Fc region of IgG
What cells is CD19 found on and whats its function?
B cell; signal transduction, CD21 co-receptor
What cells is CD21 (CR2) found on and whats its function?
B cells; receptor for complement (C3d and EBC)
What cells is CD28 found on and whats its function
T cells; receptor for costimulatory B7 molecule on antigen-presenting cells
What cells is CD40 Found on and whats its function?
B cell; signal transduction
What cells is CD56 found on and whats its function?
NK cells; adhesion molecule
What 2 markers are only found on NK cells?
CD16 and CD56
Do B cell receptors require simultaneous recognition of an associated MHC molecule to be activated?
No, antigen alone
What cell typically helps the proilferation and differentiation of B cells?
T follicular helper cell
What are B cell receptors called?
CD79a (Ig-alpha), CD79b (Ig-beta)
What does two IgG molecules do to a bacterium?
cooperate to activate complement
What antibody can cross the placenta from mother to fetus?
IgG
What is IgM in fetus serum indicative of?
the baby had an infection in the womb
What is the function of IgM?
large polymeric immunoglobulin that is good at activating complement
What is the first antibody to be secreted into the blood? What is it replaced by?
IgM; replaced by IgG
What is the main form of antibody inserted into B cell membranes?
IgD
Where is IgA found?
Found in secretions like saliva, tears, genitourinary and intestinal fluids, milk
Where does the secretory component that is found on IgA molecules come from?
epithelial cells that secrete the cells
What is the function of IgE?
attach to mast cells in tissues to cause them to degranulate
When attached to mast cells, what does IgE cause them to secrete?
prostaglandins, leukotrienes and cytokines, and release its granules of histamines
What antibody is favored in local lymphoid tissues (after infection through mucosal membranes)?
IgA, sometimes IgE
What antibodies are favored if an antigen reaches local lymph nodes or the spleen?
IgM first, then IgG
What pathogen are patients without a spleen more susceptible to?
Salmonella spp.