Immune cellular activity

Question 1

what cytokines do CD4+ Th1 cells secrete?

Answer 1

TGF beta, IFNγ (interferon gamma), IL-3, IL-10, ?IL-2 absent IL-4 and IL-5.

β γ

Question 2

What stimulates Th17 cells to produce of IL-17, and what are the consequences ?

Answer 2

Th17 cells are developed from precursor helper T cells by TGF-beta, IL-6, IL-21, and IL-23. Th17 cells are triggered by IL-6, -23, and IL-1 beta, to produce IL 21, IL-22 and IL-17.

IL-6 - a proinflammatory cytokine when acting on macrophages via NFkB activation, and aniti-nflammatory when generated by muscle contraction via IL-10 and IL1ra production.

IL-21 activates NK cells and CD8 lymphocytes that can destroy infected or cancer cells.

IL-23 and IL-12 mediate psoriatic inflammation.

IL-17 activates neutrophiles which then turn on NFkB as well as IgM, and IgA B cells.

NFkB - Nuclear Factor kappa B

Question 3

How many binding sites must connect to stimulate T helper cell activation?

Answer 3

The beta chain of the T cell receptor must recognize the antigen in the MHC class 2 groove and CD4 must associate with the T cell receptor and bind to the beta-2 domain of the MHC class 2 complex. The cytoplasmic tails of cd4 and cd3 then acriivate Lck tyrosine kinase.

Question 4

How strong is the attachment of the T cell receptor to the immunogen on the MHC molecule?

Answer 4

The binding is weak permitting easy on easy off interrogation of multiple receptors. Additional binding such as CD4 and presence of appropriate cytokines determines the T cell response.

Question 5

What do regulatory B cells secrete ?

Answer 5

Regulatory B cells (Bregs) secrete IL-10 and and TGF-beta.

Question 6

What S100 type protein is involved in psoriatic inflammation?

Answer 6

S100 proteins are calcium binding proteins with 2 helix loop helix binding sites. Unlike calmodulin they are cell type specific. The S100A7 gene codes for psoriasin which is an inflammatory cytokine in autoimmune skin conditions including psoriasis. S-100 proteins are found in melanomas, schwamnomas, neurofibromas, histiocytomas, and clear cell sarcomas. They are markers of inflammatory disease and may act as an antimicrobial.

Question 7

Arginine can generate citrulline via deimination, which might generate auto antigens from what sources?

Answer 7

Citrulline modified auto antigens include filaggrin, fibrin, vimentin, collagen, and alpha enolase. Filaggrin is a protein in the stratum granulosum of the skin, vimentin is in intermediate filaments, and alpha enolase is a glycolytic enzyme thought to be an auto antigen in Hashimoto’s encephalopathy, severe asthma, and Behcet’s disease.

Question 8

What are defensins?

Answer 8

Defensins are small cationic proteins with high cystiene content that kill pathogens by forming holes in bacterial and fungal cell membranes.

Question 9

What are immunophilins?

Answer 9

Immunophilins are highly conserved peptidyl-prolyl isomerases that bind to immunosuppressive drugs, FKBPs and cyclophilins. FKBP’s bind FK506 (Tacrolimus) and cyclophilins bind cyclosporine. Both participate in protein folding, receptor signaling, protein trafficking, transcription, apoptosis, and T cell activation. Cyclophillins are overexpressed in cancer and rheumatoid arthritis and worsen prognosis.

Cyclosporin is immunosuppressive as it binds cyclophillin which blocks calcinurin, a phosphatase, which is necessary for TNF and IL-2 production.

Question 10

What are chemokines ?

Answer 10

Chemokines are a type of cytokine, 8 – 10 kilodalton size proteins containing 4 cysteines which determine their 3 dimensional shape. They recruit immune cells to sites of infection. Some are homeostatic and control cells during physiological activity via G protein coupled receptors. They are found in all vertebrates, some viruses and bacteria, but not invertebrates.

Question 11

What does TGF-beta do?

Answer 11

TGF-β induces apoptosis through the SMAD and DAXX pathways, regulates the cell cycle through c-myc suppression, and the immune system by blocking activation of lymphocytes and monocyte derived phagocytes.

SMAD-3 types: receptor regulated, common partner, inhibitory.

DAXX- Death Associated factor 6

Question 12

What are NLR’s (NOD Like Receptor) that form an inflammasome in response to Damps (Damage Associated Molecular Patterns)?

Answer 12

An NLR is an intracelluar multidomain receptor protein that binds DAMPS, or PAMPS then forms an inflammasome which generates multiple cytokines thus provoking inflammation.

AIM2 (Absent In Myeloma 2) is an interferon-inducible protein, 344 aa, which forms part of the inflammasome responding to bacterial and viral DNA.

Other components of the inflammasome include NLRP3, ASC, and FADD as well as CASP1 and CASP8.

NOD - Nucleotide-binding Oligomerizaton Domain-. The Nacht protein component binds the nucleotide and performs the ATP depednant oligomerization.

CASP1 (Cystine-ASpartic Protease 1) becomes active changing preproIL-1beta/18 to active IL-1beta and IL-18.

NLRP3; Nacht domain, LRR, Pyrin domain-containing protein 3

LRR-Leucine Rich Repeat, signals presence of ligand

ASC: Apoptosis Spec like protein containing a Card. product of PYCARD gene

CARD: CAspace Recruitment Domain

FADD: Fas Associated protein with Death Domain

Question 13

What happens in the SMAD pathway

Answer 13

SMAD (Small body size- a worm gene, Mothers Against Decapentaplegic- a Drosophila gene) proteins transduce extracellular signals from TGF-β, activating or inhibiting downstream gene transcription. SMAD4 binds to an inhibitory site on the myc promotor thus decreasing proliferation.

Question 14

What is IL-13?

Answer 14

IL-13 is similar to IL-4 structurally, increases IgE and metalloproteinase production. It induces many features of allergic disease such as airway hyperresponsiveness, mucus hypersecretion, and Schistosoma granuloma formation.

Question 15

What is TRIM5alpha?

Answer 15

TRIM5alpha (TRIpartite Motif containing motif 5) is a 493 aa gene product retrovirus restriction factor found in most primate cells.

Question 16

How does transcription factor T-bet produce interferon?

Answer 16

T-bet from gene TBX21, binds to a T-box promoter producing T-bet which stimulates Th1 and NK cells to produce interferon gamma.

Question 17

what is GATA-3?

Answer 17

GATA-3 is the transcription factor inTh2 cells that stimulates the production of IL-4, IL 13, and IL-8.

Question 18

What type of interferon seems active in rheumatic diseases?

Answer 18

Interferon 1 inducible genes are increased in whole blood in SLE, dermatomyositis, scleroderma and in affected tissues in SLE, dermatomyositis, and rheumatoid synovium.

Question 19

What sort of effectors are stimulated by interferons?

Answer 19

interferon type I (Alpha +8 others-13 subtypes) bind to IFN-alpha/beta receptor and stimulate antiviral innate immune responses, opiate receptors to produce prostaglandins and fever and analgesia, the reduction of growth factors and angiogenesis factors by immune cells. Subtypes vary by cell of origin and species. Interferon type II binds to INFGR which in humans is INF gamma. Interferon type III stimulates receptor IL10R2, and is produced and some types of virus infections. Tetherin ( BST2-bone marrow stromal antigen 2 gene product) produced by interferon stimulation and resides in lipid rafts where it tethers encapsulated viruses to the cell membrane thus preventing viral release. Viperin is a 361 antiviral interferon induced protein with multiple domains targeting lipid rafts, mitochondria, and endoplasmic reticulum resulting in inhibition of HCMV, HCV, influenza, HIV,

Question 20

How does IL-1 work?

Answer 20

IL-1α is synthesized as a precursor protein and stored in mesenchymal and epithelial cells but must be synthesized de novo in response to stress. The precursor is modified into a 17-kDa transcription factor, and cytosolic protein which acts as a damage-associated molecular pattern molecule (DAMP). DAMP then stimulates pattern recognition receptors (PRRs) on innate immunity cells, and results in necrosis or pyroptosis of the originally stressed cell.IL-1α stimulates IL-1R

Question 21

What are DAMPs?

Answer 21

DAMP (damage-associated molecular pattern molecules) initiate noninfectious inflammatory responses and include chromatin-associated protein high-mobility group box 1 (HMGB1), major mediator of endotoxin shock; DNA and RNA mediated by TLR9 and TLR3; S100 molecules, and ATP, adenosine, and uric acid mediated by inflammasomes.

Question 22

What pathways are stimulated after IL-1 receptor activation?

Answer 22

IL-1 stimulates the transmembrane receptor IL-1R, which has many associated proteins including ACCP1, MyD88, IRAK and TRAF6. MyD88, IRAK and TRAF6 also associate with Toll like receptors. These complexes stimulate NIK which then phosphorylates IkB-alpha which is then ubiquinated and destroyed releasing p65 (RelA) and p50 (NF-kB1), transcription factors for inflammatory response-TNFα, INF.

Question 23

What sort of protein is MICA (MHC class 1 chain-related sequence A) ?

Answer 23

MICA (MHC class I polypeptide-related sequence A) encodes a highly polymorphic MHC class I protein that does not associate with beta-2-microglobulin. It is broadly recognized by NK cells, NKT cells, and T cells. It is the ligand that activates the NK cell receptor NKG2D.Alleles of this gene determine rheumatoid arthritis susceptibility.

Question 24

How many types of Treg lymphocytes are there?

Answer 24

Naturally occurring Treg cells (nTreg) are CD4+ CD25+ FoxP3+. Adaptive Treg cells are also known as Tr1, Th3, CD8+CD28+, Qa-1 restricted cells may also contain FoxP3 and function as suppressor cells. Induced Treg cells (iTreg) develop outside the thymus from mature CD4+ T cells, and function to increase TCR diversity.

Question 25

What does thymic stromal Lymphopoietin do?

Answer 25

TSLP (Thymic Stromal Lymphopoietin) induces T cell-attracting chemokines from monocytes that increases maturation of CD11c+ dendritic cells.

Question 26

What are the proinflammatory family members of the IL-1 superfamily?

Answer 26

Proinflammatory IL-1 family members include IL-1 alpha, beta, IL-18, IL 36 alpha, IL-36 Beta, IL-36 gamma and IL-33. Antagonists to other members include IL-1Ra, IL-36Ra, IL-37.

Question 27

How many members are there in the IL-1 superfamily?

Answer 27

The IL-1 superfamily has 11 members currently identified as various forms of IL-1,33,36, 37, and 38. Each one may or may not have a co-receptor as well as a receptor. Some are proinflammatory (7) in some anti-inflammatory (3). 9 members are on chromosome 2q, 1 on chromosome 11, and 1 on chromosome 9.Nomenclature reflects common use rather than systematic structural similarities.

Question 28

Are IL-1 transcripts active prior to proteolytic cleavage?

Answer 28

IL-1 alpha and IL-33 are stored in their long form and are capable of stimulating their receptor. IL-1 beta and IL-18 require proteolytic cleavage by caspace 1 to become active.IL-1 secretion occurs without use of the golgi apparatus.

Question 29

Why is IL-1 alpha considered a dual function cytokine?

Answer 29

IL-1 alpha precursor protein contains a transcription factor (ppIL-1 alpha) released via calpain (calcium activated protease). This activates synthesis of NF-kB, IL-6, TNF alpha and INFγ.

Question 30

how are Tregs cells produced in the gut which permit tolerance to most gastrointestinal antigens?

Answer 30

Tissue resident mononuclear phagocytes produce IL-1 beta which stimulates ILC3 cells (innate lymphoid) which then release Csf2 (GM-CSF). Phagocytes, and dendritic cells then produce IL-10 and retinoic acid which then cause naïve T cells to become Treg cells.ILC3 cells are ROR gamma t+ (RAR-related orphan receptor gamma).

Question 31

What does CCL2 have to do with monocytes?

Answer 31

CCL2 is C-C motif ligand 2 (MCP1 monocyte chemotactic protein 1) belongs to the CC chemokine family that recruits monocytes, memory T cells, and dendritic cells to the sites of inflammation, caused by either injury or infection.

Question 32

What is Helios?

Answer 32

Helios (IZKF2) is a zinc finger transcription factor important in lymphocyte maturation.Other family members include Ikaros, Aiolos proteins.

Question 33

What is the difference between T cell dependent and T cell independent responses?

Answer 33

T cell dependent antibody responses (TD) are elicited by proteins producing B cell activation, proliferation, and antibody production. T cell independent antibody responses (TI) are TI type I (TI-1), which need TLR support and TI type II (TI-2) which rely on extensive cross-linking leading to B cell receptor activation and IgM production.

Question 34

What is the role of endogenous retroviruses in TI-2 antibody responsiveness.

Answer 34

TI-2 responses may be depend upon endogenous retroviral activation, reverse transcriptase activation with RNA becoming DNA, stimulation of the MAVS, RIG-1 and cGAS pathways, which augment antibody synthesis. Mitochondrial antiviral signaling protein (MAVS) is an adapter for RIG-1-like human helicases (R NFkBicase). cGMP-AMP synthase (cGAS) catalyzes the synthesis of cGMP-AMP which binds and activates STING leading to type I interferon production. STING (stimulator of interferon gene) is part of the cytosolic DNA-sensing pathway The combination of affects stimulates B cell via NFkB via B cell receptor and Btk.

Question 35

What chromosomes code for light and heavy chains?

Answer 35

The heavy chain locus is at 14q 32.33, 1.25 million bases, the kappa light chain is on chromosome 2, about 400,000 bases and the lambda chain is on chromosome 22. about 900,000 bases. RAG2 (recombination activating gene 2). protein product involved in V(D)J recombination during B and T cell development. Mutations result in Omenn syndrome, a form of severe combined immunodeficiency.

Question 36

What is IgJ?

Answer 36

IgJ is an immunoglobulin, 15 kDa, with typical immunoglobulin beta pleated sheets that binds the alpha chains of IgA and mu chains of IgM. There are almost 1 trillion B lymphocytes that make more than 1 billion different immunoglobulins.

Question 37

What co-stimulator T-cell system regulates Th17 function?

Answer 37

Inducible co-simulator (ICOS, CD278) is part of the CTLA-4/CD 28 system, expressed on activated T cells, and regulates T follicular helper cells (Tfh) , and IL 23 receptor expression thereby affecting Th17 function. It also has a role in IL-2 secretion.

Question 38

What is tenascin?

Answer 38

Tenascin is an extracellular matrix glycoprotein, 190-240 kDa, 2203 amino acids. The carboxy terminus is similar to fibrinogen. Binds to syndecan. Multiple disulfide bonds and glycosylation sites. The C form is abundant in tendons, bone, cartilage. The R formed in the nervous system, the X form in this connective tissue where mutations resulted Ehlers-Danlos syndrome, and the W formed in the kidney and developing bone.

Question 39

What is viperin (virus inhibitory protein, endoplasmic reticulum-associated, interferon inducible) and how does it work?

Answer 39

viper in works on cell membrane lipid rafts via inhibiting farnesyl diphosphate synthase (FPPS) and isoprenoid synthesis to inhibit virus replication.

Question 40

What are Cathelicidins?

Answer 40

Cathelicidins are 12 to 80 amino acid residue proteins found in lysosomes and neutrophile granules that are increased by vitamin D and have a bactericidal activity. Vitamin D decreases infections in dialysis patients. They account for inflammation in rosacea where they are released by epithelial cells.

Question 41

what is LFA-1 (Lymphocyte function-associated antigen 1 )?

Answer 41

Lymphocyte function-associated antigen 1 is a heterodimer integrin CD11a (integrin alpha L, p189) and CD18 (integrin beta-2). This is present on both T and B cells and binds to ICAM-1 (CD54) on antigen presenting cells.

Question 42

What is CXCR5 ?

Answer 42

CXCR5 (CD185) is a 7 transmembrane G protein-coupled receptor for CXCL13. Secreted by T cells. CXCR5 is a follicle homing receptor. CD4+ CXCR5+ T cells protect against tuberculosis.

Question 43

What does Bcl-6 transcription factor do?

Answer 43

Bcl-6 B cell lymphoma 6 protein, a zinc finger repressor of IL-4, stimulates T->Tfh

Question 44

What is the difference between apoptosis, necroptosis, pyroptosis, and netosis?

Answer 44

Apoptosis results from nuclear disruption due to TNF and caspase 8.

necroptosis relies on RIPK1 and RIPK3, as well as TLR3, TLR4 and the T cell antigen receptor. In the absence of active caspase 8. RIP1 phosphorylates RIP3 which activates MLKL which leads to cell membrane rupture.

Pyroptosis is a form of apoptosis due to PAMPs and DAMPS acting on inflammasomes within the cytoplasm rather than TLR on the cell membrane. Pyroptosis depends on GSMD (gasdermin D) activation by Caspase to lyse the cell membrane releasing contents including IL-1beta.

Netosis comes from granulocyte disintegration wherein nuclear debris traps and kills bacteria.

RIPK1 (Receptor Interacting Protein Kinase 1)

MLKL (protein mixed lineage kinase domain like)

PAMPs (pathogen-associated molecular patterns)

DAMPs (damag-associated molecular patterns)

Question 45

How does HMGB1 (High Mobility Group Box 1 ) protein activate macrophages.

Answer 45

HMGB1 protein is secreated by macrophages, monocytes, and denderitic cells which then binds to TLR2 and TLR4 on macrophages provoking cytokine release. Antibodies to neutralise HMGB1 reduce inflammation in rheumatoid arthriris and coiitis and other types of non infectious inflammation.

Question 46

What is the cGAS-STING pathway ?

Answer 46

cGAS (cyclic GMP-AMP synthase) is a dsDNA binding enzyme that becomes activated once bound and then releases the STING (StimulaTor of INterferon Genes) protein from the endoplasmic reticulum that then phosphorylates TBK1 (TANK binding kinase 1) which phosphorylates IRF3 (Interferon regulatory factor 3) that then activates multiple interferon genes.

This pathway is separate from Toll like receptor activation, TLR7 and TLR9.

https://www.sciencemagazinedigital.org/sciencemagazine/08_march_2019?folio=1055

Question 47

How does cGMP-AMP synthase become activated by dsDNA?

Answer 47

cGMP-AMP synthase has a butterfly shape and dsDNA closes the wings and creates the enzymatic cleft.

https://www.sciencemagazinedigital.org/sciencemagazine/08_march_2019?folio=1055

Question 48

What disease models are less intense in STING K/O mice?

Answer 48

Acute pancreatitis, age dependent macular degeneration, Aicardi-Gloutiere’s syndrome, alcoholic liver disease, liver damage from CCl4, myocardial infarction, primary cancer and metastases, nonalcoholic steatohepatitis, polyarthritis, and sepsis. SLE not yet tested.

Aicardi-Gloutiere’s syndrome 1992, early childhood inflammatory destruction of skin and brain.

https://www.sciencemagazinedigital.org/sciencemagazine/08_march_2019?folio=1055

Question 49

how do bowel comensal microbes, segmented filamentous bacteria (SFB) stimulate Th17 lymphocytes to promote host resistance?

Answer 49

SFB aggregates stimulate formation of endocytic vesicles in intestinal endothelial cells that contain bacterial cell wall antigens. CDC42 (Cell Division Control protein 42) then forms endocytic vesicles capable of stimulating nearby Th17 lymphocytes. This process is termed Microbiologic Adhesion-Triggered Endocytosis (MATE).

Knocking out CDC42 markedly reduces CD4 and Th17 lymphocyte differentiation.

https://www.sciencemagazinedigital.org/sciencemagazine/08_march_2019?folio=1058

Question 50

What is an inflammasome?

Answer 50

An inflammasome is a cytoplasmic enzyme complex within myeloid cells that activates Caspases resulting in pyroptosis with inflammatory cytokine release. The composition of the complex varies by the DAMP or PAMP which stimulates the genesis of the inflammasome.

NLRP1- NOD Like Receptor Protein 1 which binds microbial products.

NLRP3 - binds viral and bacterial products, crystals-urate and cholesterol, proein aggregates, titatiam, sclica, and asbestos particles.

NLRC4 - NOD lLke Receptor family containing CARD-domain protein 4. Binds to bacterial products iinduced by flagellin stimulated entry, and palmitate.

ALR - AIM2 Like Receptor

Other bound protens aside from NLR of the inflammasome include ASC, and FADD as well as CASP1 and CASP8.

DAMPS - Damage Associated Molecular Patterns.

PAMPS- Pathogen Associated Molecular Patterns.

NLR - NOD Like Receptor. an intracellualr protein receptor that binds nucleotides as well as an LRR domain, and a Pyrin domain-containing protein 3

NOD - Nucleotide-binding Oligomerizaton Domain-. The Nacht protein domain binds the nucleotide and performs the ATP depednant oligomerization.

CASP1 (Cystine-ASpartic Protease 1) becomes active cleaving preproIL-1beta/18 to active IL-1beta and IL-18.

NLRP3; Nacht domain, LRR, Pyrin domain-containing protein 3

LRR-Leucine Rich Repeat, signals presence of ligand

ASC: Apoptosis Spec like protein containing a Card. Product of the PYCARD gene

CARD: CAspace Recruitment Domain

FADD: Fas Associated protein with Death Domain

AIM2 (absent in myeloma 2) is an interferon-inducible protein, 344 aa, which forms part of the inflammasome responding to bacterial and viral DNA withour the need for additional TLR activation.

Wikipedia 2019