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Microbiology And Immunology > Overview of the adaptive immune system > Flashcards

Overview of the adaptive immune system Flashcards

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1
Q

Principles of adaptive immune system
Why do we need the adaptive immune system when we have the innate immune system?

A
  • Allows for enhanced specifity as a consquence of previous events (exposure or vaccination)
  • Allows for memory and a anamnestic response (not forgetting)
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2
Q

Describe the purpose of adaptive immune system and why we have it?

A
  • Protection and defence against pathogens: Also role in malignancy surveillance. Also linked to damage healing and repair
  • The same pathogens often come back and attack again: Opportunity to have effectors ready which are specific and potent
  • Some pathogens stick around (in the body even after infection is resolved e.g. HSV): Need controlling by effectors
  • These effectors are primarily lymphocytes
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3
Q

How pathogens are recognised
How are pathogens spotted from the adaptive immune system?

A
  1. Generic recognisable features e.g. PAMPS
  2. Presence is associated with damage -> danger hypothesis
    2a. Damage requires co-stimulation with CD28+ cells
    2b. Recognition of Damage-associated molecular pattern molecules (DAMP)
    2c. Danger hypothesis = It is based on the idea that the immune system
    does not distinguish between self and non-self, but rather between things that might cause damage and things that will not
  3. Re-exposure to previous infections
  4. Autoimmunity -> distinguishing self vs non-self
  5. PRRs
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4
Q

Drivers of adaptive response
How does the immune system set up a system to recognise things not yet seen and describe the potential problems from this?

A
  • Undergoes a “massive array of possibilities” approach
  • Problems:
    1. Over- or under- assidious (great detail) recognition
    2. Time and energy consuming
    3. Self recognition -> can target self
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5
Q

Lymphocytes
State 3 types of B cell lymphocyte deficiency/ defect syndrome?

A
  • Congenital agammaglobulinaemia
  • Common variable immunodeficiency (CVID)
  • Novel biologics - Rituximab
  • Often leads to major life-threatening clinical problems
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6
Q

Lymphocytes
State 3 types of T cell lymphocyte deficiency/ defect syndrome?

A
  • Severe Combined Immunodeficiency (SCID)
  • DiGeorge syndrome -thymic failure
  • Acquired - HIV / Chemotherapy / Novel biologics
  • Often leads to major life-threatening clinical problems
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7
Q

State the cells found within the innate/adaptive spectrum?

A
  • Innate: Neutrophils, Monocytes, Eosinophils, basophils Macrophages, NK cells, DC cells. Tissue cells, platelets
  • Adaptive: B cells, T cells, Plasma cells
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8
Q

State the bridging cells found in the innate/adaptive spectrum?

A
  • Memory NK cells
  • iNK T cells
  • V52+ Y5 T cells
  • MAI T
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9
Q

State the 5 factors used to define lymphocytes?

A
  1. Morphology: White cell; small, large nucleus
  2. Lineage: T and B cells
  3. Location: Tissue-resident memory cells (TRM) - Marginal zone B cells
  4. Differentiation: Naïve / memory (central, effector, stem cell memory) - b. Immature / mature or differentiated / senescent
  5. Function: What they do: eg Helper / Cytotoxic / Regulatory / Antibody-producing
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10
Q

State the 4 characteristics used to show what a lymphocyte is?

A
  1. Phenotype: What surface markers they express
    -Eg CD4, CD8, CD28 … Usually functional receptors-not just there for our convenience!
  2. Specificity: What target - What Ab produced or epitope recognised (TCR)
  3. Type of receptor: Ig class for B cells / a vs y for T cells
  4. By what they produce: TH1 (IL-2, IFN-V). TH2 (IL-4, IL-5, IL-6, IL-10)
    - Key point: Dimensions (I have 9) co-exist and co-define cells
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11
Q

Mechanism of adaptive immunity
State the key features involved in adaptive immunity? (3)

A
  • Specificity
  • Memory
  • The pivotal role of clonal selection: One clone - one specificity. Progeny can be expanded and retained
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12
Q

Describe clonal selection in adaptive immunity? (PART 1)

A
  • Occurs via two key lineages of adaptive immunity -> B and T cells
  • Basic tenet - one cell one specificity •
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13
Q

Describe clonal selection in adaptive immunity? (PART 2)

A
  • For B cells - one cell, one Ig/B-cell receptor
  • Defined by their antibody
  • May class switch / undergo affinity maturation
  • But always the same basic Ig
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14
Q

Describe clonal selection in adaptive immunity? (PART 3)

A
  • For T cells - one cell, one T cell receptor - TCR
  • Selection and expansion of that clone + differentiation
  • Retention in “memory” of clonal progeny
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15
Q

Describe clonal selection in adaptive immunity? (PART 4)

A
  • Continued protection:
  • Continued production of antibody (B cells / Plasma cells)
  • More rapid specific secondary responses (Band T cells)
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16
Q

Describe the structure of an Ig, T-cell receptor and antibody?

A

VD

17
Q

Describe how TCR detects peptides presented?

A
  • TCR does not just “go fishing” in the extracellular milieu
  • Detects a peptide sequence in association with MHC
  • Pathogen peptides need to be processed and presented
  • All cells process their intracellular contents and present on MHC-1: Recognised by CD8 T cells through their TCR. Crucial to defence against viruses
  • Specialised antigen-presenting cells (APC) process and present peptides in MHC-II: Binds to TCR on CD4 T cells
18
Q

State positive and negative thymic selection of T cell?

A
  • Positive selection must bind MHC
  • Negative selection must not bind self peptides
19
Q

What occurs once thymus selection has occured for T cells?

A
  • Naive/memory cells recirculate
  • Primarily from blood to lymph nodes
20
Q

Describe the turnover rate for Naive/memory T cells?

A

They have slow turnover rates -> considered the ‘sleeping beauties’ of the immune system

21
Q

State the T-cell differentations stages and how their features change as u go along?

A

VD

22
Q

Describe differences between Central memory T cells (TCM) and effector memory (TEM)? (PART 1)

A
  • TEM:
  • Effector Memory cells
  • Short-lived population continually replenished doubling time about 15 days
  • CCR7+ CD62L+
  • Enter lymph node and recirculate
23
Q

Describe differences between Central memory T cells (TCM) and effector memory (TEM)? (PART 2)

A
  • ТСМ
  • Central memory cells
  • Turnover at a significant rate - Doubling time about 48 days
  • CCR7 - CD62L
  • Migrate into tissues
  • Rapid effector activity: Cytolytic, Cytokines (IFg/IL4/IL-5)
  • Turnover rate: TEM > TCM
24
Q

Describe regulatory T cells (Treg)?

A
  • Also very dynamic
  • Control the responses of other T cells
25
Q

Describe the key concepts behind immunological memory?

A
  • Accrued cumulatively over time
  • “Stored” for future use
  • Readily available when required
  • Dynamic process
26
Q

Describe features of B cell repertoire selection?

A
  • Positive + negative selection
  • Receptor editing
  • Transition to IgM+ IgD+ mature B cell
  • Antigen recognition leads to proliferation/differentiation
  • Activated B cells transform into Plasma cells: “Antibody factories”. also produce CD27+ memory B cell
27
Q

Lymphocyte anatomy
Describe the structure of lymph nodes? VD

A
  • Lymphocytes are mainly organised into LN
  • Structure this way to facilitate cellular interaction
  • Valves stop lymph from flowing in the wrong direction
  • Lymph flows out of the node through wide vessels
  • Lymph flows into node through narrow vessels
  • Has densely packed B and T cells, macrophages and plasma cells
28
Q

Which organ has a key role in antibody generation and describe what can increase the risk of infection if affected?

A
  • Key role of Spleen in antibody generation
  • Splenectomy increases the risk of infection
  • Especially pneumococcal infection - recommend vaccination
29
Q

Describe the role of tissue resident T cells and state its key marker?

A
  • CD69+ key marker
  • TM cells which resides long term in epithelial barrier tissues

Microbiology And Immunology (32 decks)

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