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Pom > Lymphocytes > Flashcards

Lymphocytes Flashcards

1
Q

Why do we need adaptive immunity

A

Protects us from repeat infections
Absence would lead to inability to clear infections
1)Has memory
2)needs time to develop
3)improves efficacy of innate immune response

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2
Q

What is immunological memory

A

Once an immune response has occurred it exhibits memory
More rapid andheightened immune response occurs
Reduction in severity on re exposure
Basis of vaccines

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3
Q

2 types of adaptive immune response

A

Cell mediated response: produces cytokines to help shape immune response (cd4),kill infected cells (cd8)
Humoral response:produces antibodies

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4
Q

Antigen

A

Molecule that induces an adaptive immune response

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5
Q

Epitope

A

Region of antigen which the receptor binds to

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6
Q

Which structure of epitopes do T cells recognize

A

Linear epitopes

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7
Q

What structure of epitopes do B cells recognize

A

Structural epitopes - the 3D structure of the antigen in space (recognise tertiary structure of antigen)

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8
Q

How is the adaptive immune response specific

A

Each antibody recognizes only one antigen

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9
Q

Clonal expansion

A

Occurs when an interaction between a specific foreign molecule and receptor happens

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10
Q

antigen receptor diversity problem

A
  • We need to encode a large repertoire of lymphocyte receptors to deal with antigen diversity
  • 10^15 different antibody molecules can be generated, each by a specific B cell expressing a specific BCR, therefore we need 10^15 different genes (which is impossible if 1 gene per function- we only have 25k genes in total for everything)
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11
Q

How is antigen receptor diversity generated

A
  • Through genetic recombination
  • Functional genes for antigen receptors don’t exist until they’re generated during lymphocyte development → each BCR receptor chain (kappa, lambda and heavy chains) is encoded by separate multigene families on different chromosomes
  • During B cell maturation (in the bone marrow) these gene segments brought together and rearranged- in a process called Immunoglobulin gene rearrangement (aka VDJ recombination)
  • This generates the diversity of the lymphocyte repertoire
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12
Q

What presents antigens to T cells

A

Major histocompatibility complex which is critical in donor matching and surgeey

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13
Q

What is the role of MHC

A

To bind peptide fragments derived from pathogens and display them on the cell surface of APC for recognition by the appropriate T cells

  • Plays a central role in defining self and non-self

Critical in surgery and donor matching

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14
Q

What gene in humans encodes for MHC

A

HLA genes

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15
Q

MHC expression

A

MHC is polygenic - 3 class I and 3 class II loci

  • Expression is codominant (maternal and paternal genes both expressed)

Each person can have up to 6 of the variations of the gene if completely heterozygous (3 from mother and 3 from father)

  • 17k MHC variants- is why matching people for surgery complicated- doctors trying to match 6 different things
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16
Q

MHCI

A

single variable alpha chain and common beta microglobulin
Found on all nucleated cells
Present intracellular pathogen to cd8 T cells in the cytosol

17
Q

MHCII

A

alpha and beta chains
On professional antigen presenting cells
Presented to Extracellular pathogens to cd4 T cells

18
Q

Apoptosis

A

Characterized by fragmentation of nuclear dna

19
Q

What do cytotoxic T cells (cd8) cells store and release

A

Perforin granzymes granulysin
Perforin makes holes then granzymes are injected causing a cascade of events

20
Q
  • How do CD8 cells recognise and kill infected cells?
A

1) In uninfected cells, MHC I molecules show self-peptides

2) CD8 cell scans cells, looking for non-self MHC and if it doesn’t find anything it does nothing

3) A virus infects the cell and releases its contents

4) The cell now starts making viral proteins

5) It displays these as non-self MHC

6) The CD8 cells detects the non-self MHC and attacks

7) The CD8 cell kills the virally infected cell

21
Q

CD4 helper cells types

A

Th1 - pro-inflammatory (boosts cellular immune response)

Th2 - pro allergic (boosts multi-cellular response)

Th 17 - pro-inflammatory (controls bacterial and fungal infection)

Treg (Th0) - anti-inflammatory (limits immune response)

Tfh - pro-antibody

22
Q

State the functions of IL-1, IL-2, IL-3, IL-4, IL-5, IL-6 (HOT T-BONE STEAK), and which T helper cell class are they each produced by

A
  • IL-1: fever (hot) (Th1)
  • IL-2: T cell stimulation (Th1)
  • IL-3: Bone marrow stimulation (and myeloid progenitor cells) (Th1)
  • IL-4: class switching to IgE, promote antibody production (Th2)
  • IL-5: IgA, eosinophils promote antibody production **(Th2)
  • IL-6: aKute-phase protein production, and fever (Th17
23
Q

Structure of antibodies

A

Y shaped molecule made of 2 (identical) heavy and 2 (identical) light chains- they’re divided into 2 areas- constant and variable regions- huge potential for diversity in variable region

A natural immunoglobulin molecule can have any one of five classes of heavy chain.

24
Q

3 main antibody functions

A
  • Neutralisation - antibody prevents bacterial adherence to host cell
  • Opsonisation - promotes phagocytosis
  • Complement Activation - enhances opsonisation and lyses some bacteria
25
Q

List antibody classes

A
  • IgG most abundant
  • IgM produced upon antigen invasion increases transiently
  • IgA expressed in mucosal tissues forming dimers after secretion
  • IgD
  • IgE involved in allergy and parasitic infection
26
Q

Which antibody class has highest opsonisation activity?

A

IgG

27
Q

Which antibody class has highest neutralization activity

A

IgG

28
Q

What name is given to cellular receptors that bind to antibodies

A

Fc receptors
Bind to fc region if antibodies

29
Q

What are the antibodies the B cell makes the same s

A

The BCR have unique binding site that binds to an epitope

30
Q

What do native cells need to be activated

A

Accessory signal
1) directly from microbial constituents
2)from a T helper cell

31
Q

T cell helper thymus dependant pathways

A

Antibodies made
All iG classes and memory made

32
Q

How are B cells activated by T cells

A

1) The membrane bound BCR recognises antigen

2) The receptor-bound antigen is internalised and degraded into peptides

3) Peptides associate with ‘self’ molecules (MHC II) and is expressed at cell surface of B cell

4) This complex is recognised by matched CD4 T helper cell (that has been activated by recognising an antigen presented via MHC II by an APC like a dendritic cell)

5) B cell activated by co-stimulation markers and cytokines that Tfh release

33
Q

Thymus independent path

A

Thymus Independant antigens directly activate B cells without help of T cells
Second signal provided by PAMP
Makes only igM and no memeoy

34
Q

What class of bacterial molecules provide primary and secondary stimuli for B cell activation

A

polysaccharides OR lipopolysaccharides

35
Q

MHC/TCR interactions

A

Intracellular:processed in cytosol,presented on MHCI,presented to CD8 cells
Extracellular: processed in endosomes,presented on. MHCII,presented to CD4 cells

Pom (44 decks)

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