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Immunology > Adaptive Immunity > Flashcards

Adaptive Immunity Flashcards

1
Q

Cells of adaptive immunity

A
  • B lymphocytes
  • T lymphocytes
  • NK cells- considered innate T cells because of their more innate functions
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2
Q

Epitope

A

Part of the antigen that an antibody attaches to

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3
Q

Naïve lymphocytes

A

Lymphocytes that have not encountered their antigens yet

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4
Q

B-cell receptors

A

Have B cell receptors which is an antibody on surface which is specific for a specific antigen (epitope)

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5
Q

T-cell receptors

A

Have T-cell receptors that need to be presented with an antigen by phagocytes to become activated

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6
Q

Why adaptive immunity takes time to develop?

A

Lymphocytes need to become activated first by learning to recognize their specific antigen, and then they are amplified into millions of identical clones. Clones will then become soldiers that fight infection

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7
Q

Adaptive immunity

A
  • Also called acquired immunity
  • Depends on lymphocytes found in lymphoid tissues
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8
Q

Lymphoid tissues

A

Primary
- Thymus
- Bursa of fabricius
- Peyer’s patch

Secondary
- lymph nodes
- spleen
- tonsils

Tertiary
- develop at sites of chronic inflammation

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9
Q

Where are different lymphocytes from?

A
  • T cells from thymus
  • B cells from bursa or peyer’s patch
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10
Q

Progenitor cells

A

Leave the bone marrow and migrate into primary lymphoid tissue where they develop and then migrate into secondary and tertiary lymphoid tissues

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11
Q

Lymphocytes and how you can tell them apart?

A

Cells that recognize and respond to antigens

They all look the same but can be differentiated by their characteristic surface molecules called cluster of differentiation molecules (CD)
- Possess antigen receptors required to recognize specific antigens

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12
Q

Cluster of differentiation molecules (CD)

A

The different clusters of surface molecules present on different lymphocytes
- Can include receptors for cytokines, interleukins, immunoglobulins and complement receptors

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13
Q

Workshop cluster system

A

Occurs when there are receptors that are unique to the species

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14
Q

Immunophenotype

A

Collection of surface markers on the surface of lymphocytes

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15
Q

Difference between innate vs. adaptive recognition of foreign material

A

Innate: recognize general patterns (danger signals). Use TLRs, NLRs, RIG-I

Adaptive: use antigen recognition receptors (B cell receptors and T cell receptors)

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16
Q

Recognition of antigen

A
  • T cells need presentation of an antigen by MCH II on antigen presenting cells (macrophages, dendritic cells, B cells)
  • B cells can recognize free antigens
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17
Q

What cell of the adaptive immune system to be heavily rely on for extracellular pathogens?

A

B cells

18
Q

Epitopes

A
  • All of the binding sites or parts on an antigen that a lymphocyte can recognize
  • The more foreign the antigen, the higher likelihood of immunogenicity
19
Q

Different epitope types

A
  1. Linear epitope
  2. Conformational epitope
20
Q

Linear epitope

A

Does not depend on the 3D structure of the antigen

21
Q

Conformational epitope

A

Requires two strands of the molecule to come closely together to be recognized

22
Q

Lymphocyte presence

A
  • We have lots of lymphocytes that are all different and specific for certain antigens
  • They will only become activated and begin dividing when they encounter the antigen
  • Will differentiate in the lymph organs
23
Q

Phagocytic presenting

A

Phagocytes will present to any lymphocytes they encounter until they find their perfect match

24
Q

Major histocompatibility complex (MHC) molecules

A
  • Needed for antigen presentation to the T cells
  • Peptide/antigen that is being presented will fit into binding groove/cleft formed by two domains
25
Q

Discovery of MHC

A
  • Discovered when it was determined that certain transplants were not compatible with recipients while others were fine
  • Found on white blood cells (leukocyte antigens)
26
Q

MHC in different individuals

A
  • Polymorphogenic molecules on the surface of our body cells
  • All cells in one individual express the same MHC molecules but they differ from another individual therefore there is no identical individuals in a normal population except identical twins
27
Q

Two main classes of MHC

A
  • MHCI
  • MHCII
28
Q

MHCI

A

Found on all nucleated cells (except spermocytes)

Present proteins being produced by the cell as small peptides
- Peptides that are considered self are normal and do not trigger an immune response
- If the cell is infected, then it would also present parts of the peptide that are not self and this would trigger a response

Interact with cytotoxic T cells (CD8+)

29
Q

MHCII

A

Only found on antigen-presenting cells
- Cells take up material from extracellular space through phagocytosis, into a phagolysosome where it is lysed and displayed on MHCII

Interact with T helper cells (CD4+)
- When activated, will start to release cytokines that help other cells become activated (B cells and cytotoxic T cells)

30
Q

Binding groove of MHCI

A
  • Alpha1 and alpha2 forms binding groove. Highly polymorphic, 8-10 amino acids long (peptides)
  • Alpha 3-transmembrane domain
  • Beta-2 stability
31
Q

Binding groove of MHCII

A
  • Alpha1 and beta 1 forms the binding groove, highly polymorphic (12-24 amino acids)
  • Alpha 2 and beta 2- transmembrane and stability
32
Q

MHC inheritance

A
  • Inherited from parents, one set from mother (haplotype) and one set from father (haplotype)
  • Both genes are co-dominantly expressed meaning we are using them at the same time
33
Q

Genetic diversity of the MHC

A
  • MHC molecules comprised of different subunits that provide molecule structure
  • Each subunit is encoded by specific gene that is found in a specific gene locus for that subunit
  • Each locus has multiple alleles
  • Leads to each individual having different MHC molecules
34
Q

Polygeny

A

Subunits are encoded by genes in different gene loci

35
Q

MHC are polygenic

A
  • Use multiple coding regions (gene locus) for MHC I and MHC II
  • MHC I in humans (A, B, C)
  • MHC II in humans (DR, DP, DQ)
36
Q

MHC are polymorphic

A
  • Each gene locus (coding region) there are many gene alleles
  • Alleles are then expressed on cells, but there are hundreds to choose from which makes it very unlikely that two animals will express the same MHC molecules
  • Ex. in humans, 6MHC I alleles and 8 MHC II alleles expressed on the surface (but there are hundreds to actually choose from)
37
Q

Errors contributing to polymorphism

A
  • Chromosomes misalign during meiosis
  • Chromosomes separate after meiosis DNA is exchanged between haplotypes
  • Recombination between haplotypes
38
Q

Why is MHC gene polymorphism important?

A
  • Everyone has different MHC because this ensures that we are protecting our species and preventing us all being wiped out. The individuals that are better equipped to fight pathogen will survive and pass on (survival of the fittest)
  • Evidence that choice of partners is based on a selection for individuals that are the most genetically diverse (MHC diverse)
39
Q

Everyday applications for MHC use

A
  1. Transplant immunology- if transplant and donor have different MHC they will reject each other. The closer the match, the better chance of success. Would need to destroy immune system in hopes of a far match from taking
  2. Auto-immunity- self-antigen can be mistakenly recognized and lead to improper T cell stimulation
  3. Mate selection- rodent urine contain peptide sequences able to bind MHCI. Animals will breed with MHC incompatible mates
40
Q

Three signals activate a T cell

A
  1. Antigen-specific interaction
  2. Co-stimulatory molecules
  3. Instructive cytokines
41
Q

Cross-presentation

A

Some antigen entering through the exogenous pathway is also processes via endogenous pathway (proteasomal degradation). Therefore exogenous antigen loaded onto MHCI antigens

Immunology (8 decks)

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