Partridge Flashcards
Immunology
Study of the immune system
What does the immune system do?
- Provides protection or immunity against infection disease
- Distinguishes between self and non-self
- May also recognise danger signals caused by damage to cells and tissue, e.g. cancer
What are the external threats to the body?
- Viruses
- Bacteria
- Fungi
- Protozoa
- Parasites
- Prions ?
What are the internal threats to the body?
- Cancer: danger from “altered self”
- Necrosis: danger from damaged tissue
- Prions ?
What are prions?
Prions are misfolded proteins that can transmit their misfolded shape onto normal variants of the same protein; they are involved in neurodegenerative disease
How is the immune system a “double-edged sword”?
The immune system can cause disease if inappropriately activated by attacking normal self or innocuous environmental materials
Active immunisation (vaccination)
Where the immune system is stimulated by weakened/inactive forms of a pathogen to generate a memory component, so when it comes across the pathogen again it is able to quickly respond
Passive immunisation
When immune components from an immunised source are administered to an individual
What is Herceptin?
A monoclonal antibody used to treat breast cancer that is HER2 receptor positive
What are the features of the innate immune system?
- Limited specificity
- Resistance not improved by repeat infection
- Rapid response
What are the features of the adaptive immune system?
- Highly specific
- Resistance improved by repeat infection
- Slow response
Which leucocytes are involved in the innate immune system?
- Phagocytes
- Natural killer (NK) cells
Which leucocytes are involved in the adaptive immune system?
- B lymphocytes
- T lymphocytes
What are some of the soluble factors involved in the innate immune system?
- Lysozyme
- Complement
- Interferons
Which soluble factor is involved in the adaptive immune system?
Antibodies
Neutrophils
- Main phagocyte in the blood
- Short-lived but lifespan increases when infection occurs
- Fast-moving
- Contain specialised lysosomes which release enzymes
Mononuclear phagocytes
- Monocytes in the blood, macrophages in the tissues
- Monocytes generally cycle in the blood for a few days before entering the tissues as macrophages
- Long-lived
- Help initiate adaptive responses
- Act as sentinel cells; they alert the body to infection
Natural killer cells
- Type of lymphocyte
- Kill infected cells non-specifically
- Have a possible anti-tumour role; receptors on NK cells recognise “altered self”
What are the myeloid cells?
- Monocytes
- Macrophages
- Neutrophils
- Basophils
- Eosinophils
- Mast cells
- Dendritic cells
- Megakaryocytes
What are the lymphoid cells?
- Tc cells
- Th cells
- Plasma (B) cells
- Memory (B) cells
- Natural killer cells
What type of receptors do myeloid cells have?
Pattern recognition receptors (PRRs) which recognise pathogen associated molecular patterns (PAMPs)
What are PAMPs?
Patterns of molecules or receptors that are commonly found on pathogen cells but not on human cells
Defensins
Insert into microbial cell membranes to disrupt them by forming pores
Complement
Can destroy bacterial cells directly and initiate inflammation to help phagocytes to destroy bacteria
Interferons
Proteins that interfere with viral protein replication
Lysozyme
- Found in tears and other bodily fluids
- Can break down the peptidoglycan cell walls in gram-positive bacteria
What is an inflammatory response?
An integrated local response to infection
B lymphocytes
- Made and mature in bone marrow
- Have antibodies as receptors
- They secrete antibodies into bloodstream
- Are an example of humoral immunity since antibodies are soluble
- They are used in extracellular bacterial and secondary viral infections
T lymphocytes
- Made in bone marrow, mature in thymus
- Have T cell receptors
- They kill infected host cells and make cytokines
- Are an example of cell-mediated immunity
- They are used in viral and intracellular bacterial/parasitic infections
Immunoglobin classes
IgG, IgM, IgA, IgD and IgE
IgG
- Main class of antibody in serum and tissues
- Important in secondary responses
- Involved in immune memory; made by B lymphocytes
IgM
Important in primary responses, i.e. first time you come across a pathogen
IgA
- In serum and secretions
- Protects mucosal surfaces
IgD
?
IgE
- Present at very low levels
- Involved in allergy and protection against large parasites
What are the two major subpopulations of T lymphocytes?
- T helper cells
- T cytotoxic cells
T helper cells
- CD4 +ve
- Help B cells make antibodies
- Activate macrophages and natural killer cells
- Help development of T cytotoxic cells
T cytotoxic cells
- CD8 +ve
- Recognise and kill infected host cells
Cytokines
- Can be produced by any cell under the correct conditions
- Small secreted proteins involved in communication between cells of the immune system
Immunomodulators
- Usually produced and act locally
- Bind to specific cytokine receptors on target cells
What are some of the main groups of cytokines?
- Interleukins: usually made by T cells
- Interferons (IFNs): used in viral infections and for cell activation
- Chemokines: involved in cell movement or chemotaxis
Primary lymphoid tissue
Where lymphocytes reach maturity
Secondary lymphoid tissue
Where mature lymphocytes are stimulated by antigens
