1.02 - Innate Immunity Flashcards
Compare the Innate and Adaptive Immune System with respect to:
- Presence in higher organisms
- Specificity of receptors
- Genetics behind the receptors
- Presence of memory
Innate
- Present in earlier organisms
- Relies on receptors and molecules that recognise specific patterns on pathogens
- Structure of receptors and molecules encoded in the germline and is the same for all humans
- Induce the same response the first and 100th time they recognise their pathogen
Adaptive
- Only present in higher vertebrates (arisen through evolution)
- Relies on unique receptors on lymphocytes to identify specific pathogens
- Everyone has lymphocytes with different receptors and they are unique to each person
- Remembers past pathogens and gives a faster and better response with repeated challenges (memory)
Compare the difference(s) between Innate Immune Response, The Early Induced Innate Response and the Adaptive Immune Response
Innate Immunity (Immediate: 0-4 hours)
o Infection → Recognition by preformed, non-specific and broadly specific effectors → Removal of infectious agent
Early induced innate response (Early: 4-96 Hours)
o Infection → Recognition of microbial-associated molecular patterns → inflammation, recruitment and activation of effector cells → removal of infectious agent
Adaptive Immune Response
o Infection → Transport of antigen to lymphoid organs → Recognition by naive B & T Cells → Clonal expansion and differentiation to effector cells → removal of infectious agent
What are the three components of the innate immune system?
Barriers
Cells
Circulating Proteins
Describe the Epithelium as a barrier to infection
They are the first line of defence
Are a physical barrier but also aided by mucin, cilia, antimicrobial peptides and commensal bacteria
What are some common routes of entry for microbes?
Airways GIT Reproductive Tract External Surface Wounds and Abrasions Insect Bites
Compare receptor characteristics of the Innate and Adaptive Immune systems
Innate (specific to the innate - not present in adaptive):
- Specificity is inherited in the genome
- Expressed by all cell of a particular type (e.g. macrophages
- Triggers immediate response
- Recognises broad classes of pathogens
- Interacts with a range of molecular structures of a given type
Adaptive (specific to adaptive - not present in innate):
- Encoded in multiple gene segments
- Requires gene rearrangement
- Clonal distribution
- Able to discriminate between even closely related molecular structures
Describe the Stages of infection through the skin and how, at each stage, infection is protected/prevented.
Adherence to epithelium
o Normal flora, Local chemical factors, Phagocytes
Penetration of epithelium, local infection
oWound healing induced
oAntimicrobial proteins and peptides, phagocytes and complement destroy microbes
Local infections of tissues
oComplement, cytokines, chemokines, phagocytes, NK cells
oActivation of macrophages
oDendritic cells migrate to lymph nodes to activate adaptive immunity
oBlood clotting helps limit spread of infection
Adaptive Immunity
oInfection cleared by specific antibody
oT cell dependent activation and cytotoxic T cells
Describe Macrophages
A tissue based phagocytic cell, derived from monocytes, that plays important roles in innate and adaptive immunity.
Microorganisms that cross the epithelial barrier are recognised by macrophages (through their surface receptors)
Phagocytosis then occurs
Activation of macrophages brings neutrophils to the site of infection.
Describe the basic process of phagocytosis
The microbe is surrounded by the cell membrane of the phagocyte (Macrophage) and is internalised into a phagosome.
The phagosome then merges with a lysosome to give a phagolysosome.
Within the lysosome are various proteins that produce hydrogen peroxide and hypochlorite
In this phagolysosome the microbe is then degraded.
Describe Neutrophils
Short lived cells from the blood (not present in normal tissue)
Play a key role in innate immunity as they phagocytose and remove a pathogen without the assistance of the adaptive immune system
They die soon after they have phagocytksed the pathogen
Major component of pus
Describe how Neutrophils enter the infected tissue
Chemical signals released by the activated macrophages and other tissue damage caused by the pathogen (chemokines/cytokines) activate receptors on the neutrophils and the cell wall to cause the neutrophil to leave the circulation and go to the inflamed tissue.
Describe Dendritic Cells
Multiple different types Bone marrow derived Capture antigen and take to lymph node Produce cytokines Activate T cells and affect T cell differentiation
Describe Eosinophils
Bone marrow derived lymphocyte
Involved in allergic reactions
Important in defence against extracellular parasites such as helminths
Describe Mast Cells
Major effector cells of allergic reactions.
Have abundant granules containing histamine and other active agents
Have receptors for IgE antibodies.
Binding of antibodies stimulates release of their granule contents and production of other mediators –> Hypersensitivity (allergic) reactions
What is the purpose of the inflammatory response
To deliver effector molecules to the area to aid tissue macrophages
Induce local blood clotting to stop the spread of infection
Promotes repair of tissue
