Shynra B and T cell questions Flashcards by Sarah Abdalian

What does the constant region of the heavy chain dictate?

Isotype

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What are the product(s) of cleavage of an immunoglobulin by pepsin?

Dimeric antigen-binding molecule

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What are the product(s) of cleavage by papain?

Two separated antigen-binding fragments

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What cells express MHC II?

B cells, dendritic cells, and macrophages

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What is the basic structure of a T cell receptor?

Membrane bound alpha/beta or gamma/delta heterodimer

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What is the migration of B lymphocytes to specific sites (like lymph nodes) dependent on?

Selectins

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What is the role of STAT after cytokine binding to a specific cell surface receptor stimulating a lymphocyte to undergo signaling?

The STAT dimers induce translocation to the nucleus to regulate transcription

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What type of cells have somatic hyper mutations? Does this process happen before or after antigen exposure?

B cells to increase binding affinity for epitope

After (all other processes that result in gene rearrangement aka junctional diversity and VDJ rearrange happen before)

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What is allelic exclusion?

Heavy and light chains contain both maternal and paternal derived chains however, the cell only EXPRESSES one of the chains

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What happens if an early thymocyte doesn’t have IL-7 receptors?

Apoptotic death

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Where are gamma delta T cells normally found?

In the respiratory or organs, skin, and peritoneal cavity

React more rapidly than alpha beta T cells

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What kind of receptors do NKT cells express?

TCRs generated by DNA rearrangment and junctional diversity

They can be either CD4+ or CD4+CD8+

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What do pre-B-cells express?

Igalpha and Igbeta BCR accessory models

No surrogate light chain until pro-b

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What is the function of B1 cells?

Innate related immune responses

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What naive cells loads peptide fragments into MHC class II molecules?

dendritic cells:

alpha beta complexed with invariant chain synthesized in ER
at same time extracellular proteins taken up into APCs and processed in lysome/endosome
fusion of vesicle with alpha beta with lysosome with degraded proteins
lysosomal enzymes degrade invariant chain and replace with CLIP
HLA DM exchanges CLIP and express MHC II on surface

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How are fragments of a cytoplasmic pathogen presented to Cells?

MHC class I molecules present to CD8+ T cells who destroy the infected cell

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What are Th1 cells?

CD4+ T cells that respond to INTRACELLULAR pathogens by recruiting and activating phagocytic cells specifically macrophages

PRODUCE IFN-gamma!!! activates macrophages
Receptor part of type II cytokine receptors

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What does Th2 cells produce?

IL-4 (most important) as well as IL-5 (eosinophil activation, allergies) and IL-10

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What signaling molecule does CD4/CD8 coreceptor in T cells use to activate PLC cascade?

Lck which phosphorylates ITAM

activation of protein tyrosine kinase leading to signaling cascade

What signaling molecule does CR2 coreceptor in B cells use to activate PLC cascade?

Syk (PI3 kinase) activated via signaling of Igalpha and Igbeta cytoplasmic tails of BCR after cross-linking of 2 or more BCRs

What are the initial cellular events that happen after there is antigen mediated cross linking of the BCR complex

Increased expression of IL-2 receptor causing enhanced proliferation (more time in mitosis) in response to T cell signals and increased Bcl-2 for survival

Increased expression of B7 causing enhanced APC function

Increased CCR7 so cells can migrate out of lymph nodes towards the T cell zone

What is the antigen recognition event that occurs in a lymph node during T-helper-dependent antibody response to antigen?

Naive B cells recognize intact proteins, generate peptide fragments of these proteins and present them in complexes with MHC molecules to differentiated helper T cells

What B cell responses are stimulated by CD40 ligand?

Association of TRAFs with cytoplasmic tails of CD40 molecules
Activation of NF-kB
Enhanced expression of B7
Enhanced Ig isotype switch with recombinase activity
NOT enhanced production of membrane Ig

What mechanism allows B cell to change from producing to secreting Ig?

Alternative processing of primary RNA transcripts to remove the transmembrane domain and include a secretory tail piece
Differential splicing

What does affinity maturation depend on?

Somatic mutations of V genes --> basis of Igs with different affinities

What can activate B cell antibody production without aid of T cells?

Polysaccharides (ex. ABO blood group antigen) Glycolipids Nucleic acids with multiple repeated epitopes

What causes Toxic Shock Syndrome?

Excessive activation of CD4+ T cells (binds MHCII because bacteria)

What germinal center reactions occur during antigen-dependent development of B cells?

``` Clonal expansion, class switching, somatic hyper mutation and differentiation Allelic exclusion is antigen INDEPENDENT ```

How is receptor mediated and extrinsic (cyto) apoptosis different?

Receptor mediated require susceptibility by the target cell | Extrinsic/granule mediated can target any cell

What is the seqeunce of events that causes cross presentation in dendritic cells?

``` Antigen/microbe/cell is phagocytosed and broken down in lysosomes Antigens transported to cytosol for proteosomal degradation and transported to ER where they are loaded onto MHC class I and transported to the surface ```

What does CTLA-4 compete with? What does CTLA-4 binding cause?

Competes with CD28 for binding to B7 on B cells

What cell type(s) express high-affinity trimer IL-2R(alpha beta gamma chains)

Only activated T cells CD4+ and CD8+

What happens when cytoplasmic signals are generated in response to antigen binding and co stim signals in CD 8+ cells?

Activation of TFs that up-regulate IL-2 Aggregation of TCR and CD8 Increased free intracellular Ca++ TK binding to cytoplasmic domains of CD3 and CD8 --> signaling

How can a single B cell express IgM and IgD molecules on its surface at the same time?

Through alternative RNA splicing

What is expressed on the surface of mature B lymphocytes?

CD40 MHC class II molecules CD19 IgM and IgD

Where does the synthesis of antibodies occur?

In secondary lymph organs

What does the cytoplasmic region of surface IgM consist of?

3 amino acids

What expression pattern does MHC genes have?

Codominant, both maternal and paternal expressed

What molecules mediate signal transduction following antigen binding to cell surface Ig on B cell

Ig-alpha and Ig-beta | B cells are only cell with surface Ig

What molecules mediate signal transduction following antigen binding to cell surface Ig on T cell

CD3 | TCR= heterodimer

What is CD28?

Ligand found on T cells which binds to B7 (CD80) on professional APCs Main costimulatory signal for activation of resting T-cells

How do IFN-gamma and TNF-alpha act synergistically?

Upregulate expression of MHC class II

What cells express CD40 what cells express CD40L?

``` CD40= dendritic and B cells CD40L= T-cells ```

Which isotype of antibody should be used in designing a monoclonal antibody against an extracellular pathogen?

IgG is the isotype with the greatest amount of humoral protective functions. It participates in opsonization, neutralization, complement fixation and can cross the placenta

What does double-stranded RNA-dependent protein kinase mediate?

Type I interferons: it is a serine/threonine kinase, is a component of host responses to infection and various situations of cellular stress. PKR is a key mediator of interferon (IFN) action, the first line of defense against viral infection