Immunology II - Mclean Flashcards
3 modes of cytokine action:
autocrine: act on same cell
paracrine: act on nearby cells
endocrine: hormonal, act systemically. distant.
Pleiotropy:
Redundancy:
Synergy:
Antagonism:
cascade induction:
Pleiotropy: one cytokine acting on different cells, multiple effects
Redundancy: multiple cytokine , one effect
Synergy: working together for an effect
Antagonism: cytokine blocks effect
cascade induction: a cell producing a cytokine that can act in another cell that will release another cytokine.
3 popular cytokines that macrophages secrete:
important question!
These are referred to as Inflammatory cytokines **
Macrophages: IL-1, IL-6, TNFa.
IL stands for interleukins
Know how to identify which ones are inflammatory cytokines ^^^
TH1 and TH2 relationship:
they downregulate each other.
“if you have a viral or bacterial infection, you want to activate TH1 and then th1 is going to downregulate THII.” Worm : downregulate th1 and upregulate th2.
TH1 cells: play important role in what
TH2 cells:
TH1: viral, bacterial infections (macrophages engulf)
TH2: worms, larger microorganisms (B cells produce antibodies, bind to surface of worm Fc region then binds to eosinophil)
Which cell has the Fas receptor?
Fas receptor on target cell.
Fas ligand on Cytotoxic T cell (CD8), doing the killing.
ONE WITH RECEPTOR WILL DIE
CD8 cytotoxic t cell kill mechanism:
orients LG (lytic granules) and release lytic granule to site of cell contact. Move onto next cell and go down line.
CD8 T cells release:
cytotoxins
cytokine: Interferon-y.
- this inhibits viral replication, increases processing / presentation of viral antigens via MHC class I, activates macrophages
requirements of b cell activation:
1.)crosslinking of BCR (b cell receptor): binding of epitopes close to each other.
2.)b - cell co-receptors
3.)When T-cell help is involved, must do CD40 receptor on B cell binds to costimulatory molecule CD40 ligand on T cell.
Thymus-independent antigens:
TI antigens are usually bacterial surface molecules with highly repetitive epitopes that crosslink many BCRs.
LPS bind to other receptors on B cell too.
Note: the LPS is similar to the CD40 ligand in t-dependent antigens.
problems with thymus-independent antigens:
no isotype switching
no somatic hypermutation
no memory b cell formation.
Mitogens:
nonspecifically activate b / t cells. Binds to site other than b / t cell receptors.
IMPORTANT: POKEWEED MITOGEN: stimulates both B and T cells.
superantigens:
causes of this:
antigens that bind simultaneously to CD4 TCR and MHC-II of APC in absence of a specific peptide antigen.
can cause massive T cell activation, due to this superantigen not having to bind to the specific groove to elicit a response. can interact with multiple TCRs. Thus Large cytokine release.
Example: Toxic Shock Syndrome.
Isotype switching: how are the particular isotypes determined?
determined by the cytokines released by the helper t cell.
Hyper-IgM syndrome:
absence of CD40 ligand on T cells. thus, cant isotype switch, thus, too much IgM cause no switching.
which immunoglobulin has a strong affinity to mast cells, eosinophils, basophils?
IgE.
They are almost always coated with IgE even if not bound to antigen due to insanely high affinity.
Note: mast cells generally found underneath mucosa of skin.
When does a mast cell become activated?
when antigens crosslink at least 2 IgE molecules on its surface. contents will then be released.
anaphylaxis:
type 1 hypersensitivity reaction. a systemic life threatening allergic response.
difficulty breathing, drop in BP.
where antibodies are abundant:
IgM, IgG, IgA, IgE
IgM and IgG: mainly in plasma
IgG and monomeric IgA: lymph nodes / spleen, extracellular spaces
Dimeric IgA: secondary lymphoid tissue underlying mucosal surfaces. in breast milk. AKA secretory IgA, polymeric IgA.
IgE: surface of skin, under mucosal surface.
Which antibody can travel across placenta?
mechanisms for other antibodies?
TARGET QUESTIONS
IgG can go directly across placenta.
IgA through breast milk
neutralizing antibodies:
High affinity IgG, IgA.
example of artificial passive:
example of natural passive:
artificial passive: inject horse with toxin, horse generates antibodies, inject serum into person.
natural passive: IgG directly across placenta to fetus.
Natural killer cell similar to what?
they are like cytotoxic t cells but act earlier. They are less specific. can target XYZ, but cytotoxic t cells target X or Y or Z.
they provide innate immunity against intracellular infections. cytokines can activate these NK cells.
How NK cells target cells for destruction:
1.) Reduced levels of MHC class I expression. This ->
Activates receptor NKG2D. If cell is hiding from CD8 cytotoxic t cell by downregulation of MHC class I receptor, then the activating receptor will bind, causing NK cells to release contents still.
Conclusion: Cytotoxic T cell is inhibited, but NK cell is thus activated.
2.) Antibodies. NK normally part of innate immune response, but can work with the adaptive here. NK cells interact with Fc region of antibody on target cell, orients cytotoxic granules and releases them. this mechanism is called antibody-dependent cell-mediated cytotoxicity (ADCC).
