Immunology Flashcards
What is the immune system?
A complex network of cells and soluble molecules which interact to remove a foreign object.
Defend the body but errors can occur
What is the importance of the immune system?
- Role in inflammation
- failure can cause disease
- disease symptoms are caused by the immune system reacting
- can be very beneficial to harness the power- in vaccinations and immunotherapy
What are the three outcomes when the immune system fails?
- immunopathology= tissue damage from an excessive immune response
- allergy= inappropriate response to an environment antigen
- autoimmunity= failure to distinguish self from non-self
What is immunotherapy?
Check point inhibitor therapy, inhibit T cell action
What is innate immunity?
- first defence against infection
- non-specific recognition
1. Barriers
2. cellular components
3. soluble factors
What is adaptive immunity?
Specific recognition of foreign material
Generates a memory for more rapid and vigorous response for a secondary encounter
Lymphocytes and antigen-presenting cells
What are the barriers to infection for the innate immune system?
Barriers: urinary tract (low pH and flushing), Skin (physical, chemical and microbiological), Alimentary tract (physical- peristalsis, chemical), Respiratory tract (alveolar macrophages, mucociliary escalator) Cornea/ conjunctiva (blinking and antibodies in tears)
What are the soluble factors against infection in the innate immune system?
- Complement- mediates the humoral response
- Acute phase- similar to the complement proteins but activates the complement system
- Interferons- activate cells to produce antiviral proteins
What is the complement system?
Opsonises pathogens with a layer of molecules that cells of the innate immune system have receptors for.
What are the cellular components of the innate immune system?
- Phagocytes: neutrophils, eosinophils, natural killer cells, basophils, macrophages
- Natural killer cells
- Mast cells
- Dendritic cells
What do eosinophils do?
Kill parasites
What do macrophages do?
Kill intracellular pathogens
What do neutrophils do?
Kill rapidly dividing bacteria
What do mast cells do?
- Release histamine and other granules
- trigger an inflammatory response
What do dendritic cells do?
Activate adaptive immune response
What is the process of phagocytosis?
chemotaxis— adherence— membrane activation—initiation— phagosome formation— fusion—killing and digestion— release of degenerated products
What cells perform phagocytosis?
- mononucleate leukocytes- monocytes, macrophages
- polymorphonucleated leukocytes- neutrophils, basophils, eosinophils
What are the functional classes of T cells?
- CD8⁺
- CD4⁺- T cells
- CD4⁺- regulatory cells
What do CD8⁺ cells do?
These are cytotoxic T cells
-kill virus-infected cells and target viruses
What do CD4⁺ cells do?
These are T helper Cells
- TH1= activate infected macrophages, provides B cell help, and targets microbes that persist on macrophage vesicles.
- TH2= Provide B cell help, switching to IgE, antibody production and targets helminths
- TFh= Follicular helper cell, B cell help, Antibody production, targets all pathogens
- TH17= enhances neutrophil response, targets Klebsieua pneumonia fungi, promotes barrier integrity.
What do CD4⁺ regulatory cells do?
Suppress and control T cell response when needed.
Why are T cells important?
- Control and eliminate infection
- important for immunity and vaccine response
- therapeutic applications
- major role in disease pathogenesis
- kill cancerous cells.
What do T cells recognise?
Small peptide fragments bound to MHC molecules
What is the MHC?
Major histocompatibility complex
What types of MHC are there?
MHC class I and class II
Antigen processing and presentation
- Antigen uptake
- Antigen processing
- Antigen presentation
generation of small peptide fragments bound to MHC and transported to cell surface
What is the MHC I processing pathway?
Detected by CD8 T cells
Antigens in the cytoplasm- endogenous or cytosolic- processed and presented by the MHC I
found on most nucleated cells
short peptide chain located between 2 𝛼 domains and one β domain
What is the MHC II processing pathway?
Detected by CD4 T cells, found on antigen-presenting cells- dendritic cells, Macrophages, B cells
usually, exogenous antigens that are taken up by a cell and presented.
Longer peptide chain in-between 1 β and 1 𝛼 domains
What are cytokines?
Chemical messengers that allow cellular communication, soluble and bind to specific receptors on the same cell or another cell and alter the function.
Produced locally and transiently.
Some of the important roles throughout the immune system of cytokines.
- Haemopoietic- GM-CSF
- Regulatory- IL-10
- Cytotoxic- IFN-Ɣ
- Autocrine- IL-2
What are Pattern recognising receptors?
Receptors that recognise specific patterns- such as sugars, proteins, lipids and nucleic acid motifs. Expressed by dendritic cells, conserved in Mammals, worms and plants
Recognise highly conserved microbial components
What are PAMPS?
Pathogen associated molecular patterns
What are DAMPS
Damage associated molecular patterns
What are the three complement pathways?
- Classical pathway
- MB-lectin pathway
- Alternative pathway
What is the classical pathway?
Antigen: antibody complexes
C1= C1q, C1r, C1s > C4= C4b and C4a > C2= C2a and C2b» C2a + C4b binds to C3= C3 convertase C3a and C3b > C5 convertase= C4b2a3b
What are the differences in MHC I and MHC II?
- Variable binding Cleft is polymorphic
2. Related conserved regions- not involved in binding have minor differences
