OE L21 Basic Immunology Flashcards
Where do T and B cells develop?
T cells: thymus
B cells: bone marrow
What 2 responses is host immunity divided into?
- Innate immunity (non-specific)
- Adaptive immunity (antigen-specific)
Describe the main features of innate immunity.
- Non-specific
- Fast response
- First line of defence
- No memory
- Alarms and intiates adaptive immunity
What are the cell types involved in innate immunity?
- Epithelial cells of mucosa and dermis
- Endothelial cells
- Fibroblasts
- Phagocytes
- Natural killer cells
- Innate lymphoid cells
- Innate T cells
Describe the role of mucosal epithelial cells in innate immunity.
- Tight cell junctions = strong physical barrier
- Produce cytokines and chemokines in response to pathogens damaging this barrier
Describe the role of fibroblast cells in innate immunity.
- Present in the lamina propria
- Produce collagen to aid tissue repair
- Can prevent pathogens penetrating deeper
- Recruit other immune cells in repsonse to bacterial products
Describe the role of neutrophils in innate immunity.
- Produced and secreted in response to chemokines
- Phagocytic activity
- Produce ROS and RNS (reacitve oxygen/nitrogen species)
- Produce enzymes, e.g. MMPs, to facilitate immune cell infiltration
Describe the role of macrophages in innate immunity.
- Migrate to site of infection in repsponse to chemokines
- Phagocytic activity
- Produce ROS, RNS, enzymes and antimicrobial peptides
- Produce cytokines to signal to immune system and recruit more immune cells
Describe the role of dendritic cells in innate immunity.
- Phagocytic activity
- Take pathogens, migrate them to draining lymph nodes to activate adapative immune response - act as antigen presenting cells
Describe the role of mast cells, basophils and eosinophils in innate immunity.
- Produce histamine
- Dilates BVs to allow more immune cells and serum to infection site - causes swelling
- Phagocytic activity
Describe the role of natural killer cells in innate immunity.
- Important in viral infection and cancers
Describe the role of innate T cells in innate immunity.
- Belonging to T cell group
- Do not recognise specific antigens
- Has a T cell receptor of gamma delta chains
Describe the role of innate lymphoid cells in innate immunity.
- Abundant in intestinal mucousal
- Mainly involved in immunity of mucosa
How do innate immune cells recognise pathogens?
Innate immine cells have PRRs on their intra or extracellular cell surfaces- pattern recognition receptors.
What are the 4 major groups of PRRs?
- TLRs: toll like receptors
- CLRs: c-type lectin receptors
- NLRs: NOD like receptors
- RLRs: RIG like receptors
Describe the main features of adaptive immunity.
- Slow development
- Specific
- Has memory
- Long lasting
- Initiated by dendritic cells (antigen presenting cells)
Where do T and B cells mature, and where do they then travel to?
T cells mature in the thymus, B cells in the bone marrow.
Travel to lymph nodes and spleen where they remain until immune system is triggered and they’re required.
Describe the structure of a lymph node in relation to the immune cells.
- Have a T cell zone (most inner zone)
- Have a B cell zone
Germinal centres in B cell zone where B cell proliferation and maturation takes place.
What is the B cell marker?
CD19.
- B cells develop in bone marrow
- Antibody producing cells
- Humoral immunity (antibody mediated immune response)
What is the T cell marker?
CD3.
- T cells develop in thymus
- Produce cytotoxic cells and T helper cells
- Cell mediated immune response
What are the 3 functions of B cells?
- Antibody production
- Presentation of antigens to T cells
- Cytokine production
Each naive B cell expresses a B-cell receptor, what happens when an antigen binds to this receptor?
The B cell undergoes proliferation and matures into an antibody producing cell as well as producing memory B cells.
What are the functions of antibodies?
- Block entry of virus into cells
- Neutralise toxic domain of pathogens
- Aggregation causes soluble antigens to become insoluble
- IgG is an opsonin so makes pathogens more susceptible to phagocytosis
What are the 5 major antibodies in humans and briefly describe each one.
- IgA: found in saliva as a secretory antibody
- IgD: cell surface antibody serves as B cell receptor
- IgE: antigen binding can trigger histamine release from mast cell
- IgM: produced at early stage of infection, isotype switch to IgG
- IgG: most stable antibody in serum and involved in immune memory
Why do most vaccines require 2 doses?
- Because the primary response produces antibodies at a low level
- Second injection produces much high levels of antibodies
All T cells are ? positive.
All T cells are CD3 positive.
T cells can have one of 2 types of receptor, what are these 2 receptors?
- Alpha beta chain receptors: Ig like domain, 95% of T cells have this receptor
- Gamma delta chain receptors: role in innate immunity, small population in peripheral blood, abundant in gut and skin
What are the 2 main groups of T cells?
- Cytotoxic T cells (CD3+, CD8+)
2. T helper cells (CD3+, CD4+)
What are the roles of cytotoxic T cells?
- Deal with intracellular pathogens
- Produce cytokines
- Lysis cell by producing perforin and granzyme B
What are the 4 types of T helper cell?
- Th1: promote activity of macrophages and NK cells
- Th2: help B cells for antibody production
- Th17: role in inflammation and tissue damage
- Treg: suppress auto-immune response and have control over immune reactions
What are the 3 key signals for T cell activation?
1st signal: antigen presenting
2nd signal: CD28 receptor on T cell binding to ligand on dendritic cells
3rd signal: cytokine production by dendritic cells determines T cell differentation type
When a T cell binds a receptor of an antigen presenting dendritic cell what can happen?
T cell proliferates and becomes cytotoxic T cell or memory T cell
What is inflammation?
A host response against harmful stimulation (pathogens, tissue damage, chemical attack)
Compare acute and chronic inflammation.
Acute inflammation: increased blood flow and permeability, migration of neutrophils and immune cells to specific site.
Chronic inflammation: result of unresolved acute inflammation. Greater macrophage and lymphocyte migration- sometimes forms a granuloma.
What is immune hypersensitivty?
Term used to describe undesirable reactions produced by normal immune system.
What are the 4 types of immune hypersensitivity?
- Type I: IgE mediated, activates mast cells to release histamine
- Type II: IgG and IgM mediated, triggers NO release to dilate blood vesels causing serum proteins to leak
- Type III: IgG forms immunocomplex to activate mast cells to release histamine
- Type IV: delayed type IV hypersensitivity. Not antibody mediated. T-cell mediated (CD4 T cells).
Describe delayed type hypersensitivty.
- Mediated by CD4 T cells which divide into Th1 or Th17 cells
- Produces nitrous oxide, causes tissue damage
- Can join macrophages to become osteoclasts -> bone resorption
Involved in periodontitis.
Name 5 diseases related to immune system dysregulation.
- Allergies (hayfever, asthma)
- Tuberculosis
- Periodontitis
- Autoimmune diseases e.g. rheumatoid athritis
- Chronic wound healing
