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Lymphocytes Flashcards

1
Q

What is adaptive immunity

A

Antigen Specific immunity

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2
Q

What is innnate immunity

A

Non specific immune response that occurs hours within an antigen coming into the body

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3
Q

Why do we need adaptive immunity

A

Protects from repeat infections with the same pathogen . Lack of adaptive immunity can lead to SCID. But have risk of autoimmunity

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4
Q

Hallmarks of adaptive immunity

A

Improves the efficacy of the innate immune response
Focuses a response on the site of infection and the organism responsible
Has memory
Needs time to develop

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5
Q

Immunological memory is characterised by ….

A

A more rapid and heightened immune reaction .

Antigen specific lymphocytes ( B and T ) are the cellular basis

Basis for vaccines

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6
Q

Two types of adaptive immune response

A

T cells and B cells

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7
Q

T cells

A

Cell mediated response .

Produce cytokines to help shape immune response ( CD4)

Kill infected cells (CD8)

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8
Q

B cell response

A

Humoral - produce antibody

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9
Q

How do T cells recognise pathogens

A

Recognise linear epitomes in context of MHC

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10
Q

How do Antibodies/ pathogen recognise antigens

A

Antibodies recognise structural epitopes

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11
Q

What is an antigen

A

Molecules that can induce an adaptive immune response ( mostly protein)

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12
Q

What is an epitope

A

The region of an antigen which the receptor binds to

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13
Q

Clonal selection

A

• Each lymphocyte bears a single, unique receptor
• Interaction between a foreign molecule and that receptor leads to activation
Clonal Selection//Expansion
• Differentiated effector cells of that lineage will bear the same receptor
• Self specific receptors are deleted early in development

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14
Q

Functional genes from antigen receptors do not exist until they are generated during…..

A

Lymphocytes development

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15
Q

How is B cell diversity created ?

A
  • Each BCR receptor chain (kappa, lambda and heavy chain genes) is encoded by separate multigene families on different chromosomes
  • During B cell maturation these gene segments are rearranged and brought together
  • This process is called Immunoglobulin gene rearrangement
  • Immunoglobulin gene rearrangement generates the diversity of the lymphocyte repertoire
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16
Q

What are the three types of chains on BCR receptors

A

Kappa, lambda and heavy chain genes

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17
Q

How do T cell receptors have diversity

A

VCJ rearrangement

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18
Q

What is the Major histocompatability complex

A

Plays a central role in defining self and not self . Presents antigens to T cells and is critical in surgery and donor matching

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19
Q

MhC1

A

All nucleated cells although at various levels. Has a single variable alpha chain plus a common beta microglobulin molecule

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20
Q

MHC2

A

Normally only on professional antigen presenting cells - has 2 chains , alpha and beta

21
Q

MHC gene Expression

A

It is encoded by HLA genes in humans ( human leukocyte antigen)
Polygenic - 3 Class 1 and Class 2 loci
Expression is codominant so maternal and paternal genes are both expressed

22
Q

What class of MHC cell is CD8

A

MHC1.

Type= intracellular pathogen/antigen
Processed in cytosol
Present on MHC1
Presented to CD8 T cells

23
Q

What class of MHC does CD4 cells bind to

A 
CD4 binds to B2 domain of MHC class 2. 
Type of pathogen : extra cellular pathogen/antigen 
Processed in endoscopes
Presented on MHC 2 cells 
Presented to CD4 cells
24
Q

Different classes of T helper cells and the cytokines they release

A

Cytokines have diverse actions on a wide range of cells and cytokines influence the outcome of the immune response

25
Q

TfH

A

Pro antibody

IL 21

26
Q

Th 1

A 
Pro inflammatory 
Boost cellular immune response 
Interferon gamma
Tumour necrosis factor 
IL 12 - fight off virus
27
Q

T reg ( Th 0)

A

Anti inflammatory
Limit immune response
iL 10 and TGF beta

28
Q

Th2

A

Pro allergic
Boost multicellular response
IL4, IL5, IL13

29
Q

Th17

A

Pro inflammatory
Control bacterial and fungal infection
IL17, IL23, IL6

30
Q

Cytotoxic T cells

A
  • Cytotoxic T cells (CTL) kill their targets by programmed cell death = apoptosis
  • Apoptosis is characterized by fragmentation of nuclear DNA
  • CTL store perforin, granzymes, granulysin in cytotoxic granules released after target recognition
  • Perforin molecules polymerise, form pores
31
Q

Apoptosis vs necrosis

A

Better that cell dies by apoptosis as then the cell contents are not released unlike in necrosis

32
Q

How do CD8 cells kill infected cells

A
  1. In uninflected cells, MHC1 molecules show self peptide
    CD8 scan cells looking for non self MHC
    Virus infected cell and releases contents
    Cell now starts making viral proteins
    Displays theses as non self MHC
    CD8 cells detect the non self MHC and attacks
    CD8 cells kill virally infected cells
33
Q

What are the 3 core protective roles of antibodies

A
  1. Neutralisation
  2. Opsonisation
  3. Complement activation
34
Q

Neutralisation

A

Binds active site on viru or bacteria and stops virus entering into host cell

35
Q

Opsonisation

A

Make bacteria more likely to be phagocytosed

36
Q

Complement activation

A

Leads to death of anything antibody is bound to . Antibody activates complement which also enhances opsonisation and loses some bacteria

37
Q

Types of antibodies

A 
IgG
IgM
IgA
igD
IgE
38
Q

IgG

A

Highest opsonisation and neutralised activities . Has 4 classes IgG1- IgG4)

39
Q

IgM

A

Produced first upon antigen invasion . Increases transiently

40
Q

IgA

A

Expressed in mucosal tossues and forms dimes after secretions. Less inflammatory than IgG

41
Q

IgD

A

Unknown function

42
Q

IgR

A

Allergy and defence against multicellular organisms

43
Q

Where does the specificity of a B cell lie

A

B cell receptor for antigen

44
Q

BCR

A

BCR have a unique binding site which binds to a portion of the antigen called antigenic determinant or epitope . Is made before the cell ever encounters antigen

45
Q

Stimulation of B cells

A

Naive antigen specific lymphocytes cannot be activated by antigen alone. Naive B cells require accessory signal .

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

46
Q

What kind of antigen do B cells bind

A

Soluble antigen

47
Q

How is antibody production by B cells achieved

A

1) T helper cell - thymus dependent . All IgG classes and memory . This produces antibodies
2) Microbial constituents and thymus independent . Only IgM and no mememory

48
Q

Thymus independent antigens

A

Directly activate B cells without help of T cells. often polysaccharide needs to have a repetitive structure, e.g bacterial surface sugars . The second signal required is provided by a microbial PAMP , LPs

49
Q

Activation of B cells by T cells

A

Membrane bound BCR recognises antigen
The receptor bound antigen is internalise and degraded to for, peptides
Peptides associate with self molecules ) MHC2) and are expressed on cell surface
Complex is recognised by matched CD4 T cell
B cell is activates

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