Immunology Flashcards
(40 cards)
Give the definition of immunity
state of being insusceptible or resistant to a noxious agent or process
What are the first lines of defence against pathogens by humans?
Skin
Saliva/mucus/tears
Cilia
Stomach acid
urine flow
Microbiome
How does saliva act as a line of defence against pathogens?
Anti-microbial peptides and lysozymes digest bacterial cell walls.
It transports pathogens out of the body or into the stomach
How can pathogens be identified by the immune system?
They have pathogen-associated molecular patterns (PAMPs) which are specific to them. E.g LPS (lipopolysaccharides) in gram-negative cell walls
Toll-like receptors (TLRs) recognise PAMPs.
What normally expressed TLRs?
Macrophages, dendritic cells and neutrophils
What type of leukocytes are involved in innate and adaptive immunity respectively?
Myeloid cells-innate
Lymphoid-Adaptive
What effect does Inflammation have for immunity?
Blood vessels dilate, making them permeable to immune cells. Endothelial cells become sticky, allowing white blood cells to be captured
Fever inhibits pathogen proliferation
What are neutrophils?
Short lived phagocytes which migrate to sites of infection
What are macrophages?
Long lived phagocytes which are abundant in areas exposed to pathogens
What are eosinophils?
Specialist cells which attack objects too large to engulf
What are dendritic cells?
Cells which migrate to lymphoid tissue, activates and stimulates T-cells
Phagocytoses pathogens and cleaves peptides bound to MHC proteins
Outline adaptive immunity
Highly specific responses to pathogens. Involves lymphocytes developing in thymus and bone marrow.
They encounter foreign antigens in secondary lymphoid organs
Body produces lots of lymphocytes and those with binding affinity to antigens are activated
What are natural killer cells?
Early defence against foreign cells
Considered part of the innate immune response despite being lymphoid
Explain cytotoxic T cells
Directly kill infected host cells
Explain helper T cells
Activate macrophages, dendritic cells, B-cells and cytotoxic T-cells. Secrete cytoines
Explain regulatory T cells
Inhibit T helper cell function, cytotoxic T-cells and dendritic cells. Allows negative feedback
What secretes antibodies?
B-cells
How can immune tolerance to tested experimentally?
- Knockout self protein genes
- Allow the animal to grow and reintroduce its self protein
- An immune response occurs as it hasn’t encountered the protein before
How do immune systems build self-tolerance>
Lymphocytes that bind to a self-antigen die via apoptosis
Receptor editing on lymphocytes recognising self antigens
Clonal inactivation where self-reactive lymphocytes are inactivated
Clonal suppression where regulatory T cells suppress activity of self-reactive lymphocytes
What are IgGs made up of?
2x Constant domains (220aa each)
2x Variable domains (110aa each)
How are IgG variable domains encoded?
40V domains, 25D domains, 6 J domains and 5 C domains.
These are combined via V(D)J recombination
This splicing creates a unique combination of domains that are transcribed
What do mutations in RAG1 and RAG2 create?
SCID (severe combined immunodeficiency) as these genes encode V(D)J recombinase. This leads to non-functional antibodies
How do antibodies multiply so quickly?
Antigen-driven somatic hypermutilation: A range of antibodies are made by the ones with affinity to the antigens survive. This is affinity maturation
Why do B cells mutate 1 million times faster than the background rate?
Mutations are driven by activation-induced deaminase (AID) which is expressed in germinal centres. This leads to hyper mutation
