4) Basic Immunology Lectures and Diseases Specific Lectures Flashcards
What are the 3 +Coreceptors for the BCR?
CD21/19/81 (CD21, also known as complement receptor 2 or CR2, binds to C3d on antigen)
What is the -coreceptor for the BCR?
CD22
What are the signaling components of the BCR (Iga and Igb)?
First tyrosine kinase (src family): Blk, Fyn or Lyn (phosphorylate BCR’s
ITAMs)
Second tyrosine kinase (syk family): Syk
What are the coreceptors for the TCR?
CD4 or CD8 (binds to MHC Class II or I, respectively) which can bring in lck to the synapse
What the sigaling components of the TCR? (Signaling from the TCR (from CD3: e (2), d, g, z(2)))
First tyrosine kinase (src family): Fyn or Lck phosphorylates CD3 ITAMs
Second tyrosine kinase (syk family): Zap-70 activated by Lck, Zap70 in turn activates PLC-g, etc)
Signal transduction Calcium Pathways: Src kinase -> phosphorylated ITAMs -> (X) (BCR) or (Y) (TCR) -> phosphorylated adaptor protein ((Z) for BCR or Lat for TCR) -> (A) activation -> PIP2 is cleaved into (B) -> Calcium influx (2 influxes)
X = Syk Y = Zap-70 Z = Lab A = PLCg B = DAG and IP3
What are the 2 influxes of calcium in the calcium pathway?
1) First influx: IP3 binds to IP3R on ER, leading to calcium efflux from ER. The drop in ER calcium leads to STIM1 (on ER membrane) activation which signals Orai (on cell membrane) to form the CRAC channel and allows…
2) Second, larger, influx: Significant calcium influx from OUTSIDE the cell
Calcium Pathway: Higher calcium levels lead to (X) -> (Y) activation, which de-phosphorylates (Z) -> (Z) goes to the nucleus, leading to (A) transcription and proliferation.
X = calmodulin Y = calcineurin Z = NFAT A = IL-2
Cyclosporin A: key immunosuppressive drug that binds to (X) (cytoplasmic proteins) and as a complex they inhibit (Y), preventing its activation by calcium (thus blocking (Z) activation).
X = cyclophilins Y = calcineurin Z = NFAT
Tacrolimus (also known as (X)) is also an immunosuppressive drug and it works
similarly to cyclosporine. Tacrolimus ultimately prevents the dephosphorylation of
(Y)
X = FK-506 Y = NFAT
Tacrolimus: Mechanism: FK-506 binds to (X) (FK506 binding protein) to create a new complex which inhibits (Y).
Effect: Inhibits T cell (Z) and (A) transcription.
X = FKBP Y = calcineurin Z = signal transduction A = IL-2
Jak/Stat: Some cytokine
receptors associate with
(X). Cytokine binds to its receptor -> dimerization -> phosphorylation of the receptor and activation of the (X) -> Stats are recruited to the JAKs and are (Y) -> Stats (Z) and go to (A)
X = Janus kinases (JAKs) Y = phosphorylated Z = dimerize A = Nucleus
Costimulation: “Second signal” expressed on (X) cells that indicates “danger”, and is required for full activation of (Y) cells. [Signal 1 without Signal 2 -> anergy = functional inactivation, T cells are viable but don’t proliferate]. After activating costimulatory molecules turn the immune response on and the antigen has been eliminated, (Z) costimulatory molecules then turn the response off and there’s a return to homeostasis.
X = antigen presenting Y = T Z = inhibitory
Activating costimulatory molecules include:
B7-1/B7-2 (on the APC) interacting with CD28 (constitutively expressed on T cell surface). Engagement of CD28 leads to T cell expansion, differentiation, and survival
ICOSL (on the APC) interacting with ICOS (expressed at low levels on resting naïve T cells and quickly upregulated after TCR ligation and CD28 costimulation)
Regulates Tfh-B cell interactions in the germinal center. Different effects on T cell depending on the cell’s developmental stage, but important in promoting survival, proliferation, and memory in activated effector T cells and regulatory T cells
Inhibitory costimulatory molecules include:
iB7-1/B7-2 (on the APC) interacting with CTLA-4 (mostly upregulated after T cells have been activated). Engagement of CTLA-4 inhibits IL-2 production, blocks cell cycle progression, and inhibits proliferation.
PD-L1 (on B cells, T cells, DC, macrophages)/PD-L2 (on DC, macrophages) interacting with PD-1 (upregulated on T cells and B cells). Thought to have a more tissue-specific function than CTLA-4. Limits autoreactivity and establishes self-tolerance
Costimulation matters because its of huge therapeutic interest!
i. Blocking activating costimulatory molecules is a strategy being used to treat
(X) diseases (e.g. rheumatoid arthritis) and (Y).
ii. Stimulating activating costimulatory molecules or blocking inhibitory costimulatory molecules is used to boost (Z) immunity
X = autoimmune Y = transplant rejection Z = anti-tumor
How many primary immune deficiencies have been identified by the International Union of Immunological Societies?
Over 120
Immunodeficiencies: Combined T and B-cell immunodeficiencies (e.g. SCID)
1) DiGeorge syndrome
2) Rag, Artemis, IL-7Ra, ADA
3) X linked: Common Gamma chain
Immunodeficiencies: Predominantly antibody deficiencies (e.g. Bruton’s agammaglobulinemia)
Hyper-IgM syndrome
Immunodeficiencies: Other well defined Immunodeficiency syndromes. Give examples:
Wiskott-Aldrich, DNA repair defects like ataxia telangiectasias
Immunodeficiencies: Diseases of immune dysregulation. Give examples:
1) IPEX: due to FoxP3 mutation, lack of Tregs causes autoimmune enteropathy, dermatitis, autoimmune endocrinopathies, and autoimmune skin conditions.
2) APECED: due to AIRE mutation, there is lack of central tolerance in the thymus; there is lymphocyte infiltration into multiple endocrine tissues
3) XLP: Lack of SAP protein leads to widespread immune activation and lack of control of Epstein-Barr virus, which often leads to death from bone marrow
failure, hepatitis, and malignant lymphoma
Immunodeficiencies: Congenital defects of phagocyte number, function, or both: LAD1
LAD1: B2 integrin (also known as (X)) defect. (X) is a component of integrins including LFA-1, leading to failure of neutrophils to extravasate from the bloodstream to get to inflamed tissues through binding to (Y) on the endothelium. The major problem is in leukocyte (Z) the endothelium.
X = CD18 Y = ICAM-1 Z = sticking to
Immunodeficiencies: Congenital defects of phagocyte number, function, or both: LAD2
LAD2: lack of (X), which is a ligand of (Y) on the vascular endothelium, together with the (Z) blood phenotype. There is a failure of neutrophil extravasation because of lack of (A).
X = sialyl-lewis X Y = P and E-selectin Z = Bombay A = rolling
Immunodeficiencies: Congenital defects of phagocyte number, function, or both: LAD3
LAD3: lack of activation of all (X) integrins leading to a failure of (Y)
X = beta Y = extravasation
Immunodeficiencies:
Congenital defects of phagocyte number, function, or both: Chronic granulomatous disease
Lack of functional (X), with pneumonia, abscesses, suppurative arthritis, osteomyelitis, bacteremia,
fungemia, cellulitis and impetigo. People with CGD are more prone to (Y)
bacteria and the fungi (Z). Catalase produced by
bacteria breaks down the (A) species made by the cells, and without (X), the bacteria can survive.
X = NADPH oxidase Y = catalasepositive Z = Aspergillus and Candida A = reactive oxygen
Immunodeficiencies:
Congenital defects of phagocyte number, function, or both: Chediak-Higashi syndrome
Mutation in a (X) trafficking regulator protein, leading to decreases in phagocytosis and increased (Y) infections.
X = lysosomal Y = pyogenic
Immunodeficiencies: Defects in innate immunity (e.g. NEMO deficiency). Usually associated with (X) problems.
Mendelian susceptibility to mycobacterial infection: (Y)
TRIF, TLR3 and UNC93B deficiency: susceptibility to (Z)
X = skin Y = IL-12, IL-12R Z = herpes encephalitis
Immunodeficiencies: Autoinflammatory disorders (e.g. Familial Mediterranean fever). Excessive inflammation
causes (X) damage.
X = long-term
Immunodeficiencies: Complement deficiency (e.g. C1q deficiency that may predispose to lupus, C1-inhibitor deficiency that causes (X), paroxysmal nocturnal (Y))
X = hereditary angioedema Y = hemoglobinuria
Deficits in adaptive immunity are usually (X) and treatable by stem cell transplant (in the case of SCID) or (Y) replacement (in the case of antibody failure)
X = X-linked Y = immunoglobulin
Deficits in innate immunity are usually (X) gene defects (autosomal recessive) and difficult to treat
X = homozygous
The nature of the patient’s infection can provide a clue about what the immune deficiency is. For example, recurrent pyogenic bacterial infections (e.g. otitis, pneumonia, meningitis, osteomyelitis) after ~6 months of age (when protection by maternal IgG has waned) is indicative of an (X) deficiency.
X = antibody
Mechanisms of tolerance are driven by strength of TCR interaction with (X) and location of this
interaction
X = MHC and peptide
Central Tolerance (during thymic T cell or bone marrow B cell development):
o Deletion: if interaction with antigen is (X), cells die by negative selection
o Inactivation: if interaction with antigen is (Y)
o Deviation: T cells can become Tregs through (Z)
X = too strong Y = somewhat strong Z = positive selection
Peripheral Tolerance o Deletion o Inactivation: through (X) o Deviation: peripheral (Y) o Ignorance: don’t encounter antigen with signal 2 o Helplessness o (Z)
X = anergy Y = Tregs Z = Suppression
What’s a Treg?
A subset of CD4+ T cells that suppresses the activation and effector functions of other T cells that could be self-reactive.
How can you identify a Treg?
1) On the cell surface, expresses high levels of (X) and obviously CD4.
2) Expresses the (Y) transcription factors.
3) Secretes (Z) when activated
X = CD25 Y = FoxP3 and STAT5 Z = TGF-beta and IL-10
How are Tregs formed?
§ “(X)” Tregs are formed in the thymus, when a CD4 T cell recognizes (Y)
§ “(Z)” Tregs are formed in the periphery.
§ (A) are necessary for the development of Tregs (at least in vitro), and they
are produced by functioning Tregs. This production of (A) is critical for the suppressive effect of Tregs
X = Natural/Central Y = self antigen Z = Induced A = TGF-beta and IL-2
In what physiological/pathophysiological processes do Tregs play a role?
Autoimmune diseases (inflammatory bowel disease, type 1 diabetes, multiple sclerosis, skin diseases)
Allergic diseases (food sensitivity, asthma),
Inflammatory diseases
(atherosclerosis, obesity)
Tumor responses, etc.
People born without (X), the “master regulator” for Treg maturation and maintenance,
develop a multi-organ autoimmune disease called (Y)
X = FoxP3
Y = IPEX (immune dysregulation
polyendocrinopathy enteropathy X-linked inheritance)
People born without (X), a transcriptional elongation regulator which leads to
expression of peripheral antigens in medullary thymic epithelial cells (mTECS), develop a multi-organ autoimmune disease against endocrine tissues called (Y).
X = AIRE
Y = APECED (autoimmune
polyendocrinopathy-candidiasis-ectodermal dystrophy)
Immune Reactant of Type I Hypersensitivity:
IgE
Immune Reactant of Type II Hypersensitivity
IgG
Immune Reactant of Type III Hypersensitivity
IgG
Immune Reactants of Type IV Hypersensitivity
Th1, Th2, and CTLs
Antigen and Effector mechanism of Type I Hypersensitivity
Soluble antigen
Mast Cell activation
Antigen and Effector mechanism of Type II Hypersensitivity
Cell or matrix associated antigen
FcR+ cells (phagocytes, NK cells)
Antigen and Effector mechanism of Type III Hypersensitivity
Soluble antigen
FcR+ cells, Complement
Antigen and Effector mechanism of Type IV (Th1 cells) Hypersensitivity
Soluble antigen
Macrophage activation
Antigen and Effector mechanism of Type IV (Th2 cells) Hypersensitivity
Soluble antigen
Eosinophil activation
Antigen and Effector mechanism of Type IV (CTL cells) Hypersensitivity
Cell associated antigen
Cytotoxicity
Examples of Type I Hypersensitivity Reaction
Allergic rhinitis, asthma, systemic anaphylaxis
Examples of Type II Hypersensitivity Reaction
Some drug allergies (e.g. penicillin)
Examples of Type III Hypersensitivity Reaction
Serum sickness, Arthus reaction
Examples of Type IV (Th1) Hypersensitivity Reaction
Contact dermatitis, tuberculin reaction
Examples of Type IV (Th2) Hypersensitivity Reaction
Chronic asthma, chronic allergic rhinitis
Examples of Type IV (CTL) Hypersensitivity Reaction
Contact dematitis
Protection against extracellular bacteria and extracellular fungi
Antibody, complement, neutrophils, Th17 cells, ILC3s (Th17-like)