Principles of Immune Responses Flashcards
Explain the importance of immunology for human health
To identify and eliminate harmful microorganisms and harmful substances such as toxins - by distinguishing ‘self’ from ‘non-self’ + identifying ‘danger’ signals, including tissue damage.
The immune system must strike a balance between clearing the pathogen and causing collateral damage to the host - “immunopathology”.
The host therefore relies on a flexible and rapid immune response.
Our most polymorphic (variable) genes are those that control the immune response: this variation has been, selected for by exposure of populations to infectious diseases.
Describe Innate Immunity?
Recognise molecular pattern → Hundreds of receptors → Germline encoded.
Advantages: Many cells can express the same receptor, allowing a rapid, effective response.
Disadvantages: Limited receptor diversity, some pathogens may not be efficiently recognised.
Innate Immunity - PAMPs?
Pattern Recognition Receptors (PRRs):
Bacteria: flagellin, peptidoglycans, formyl peptides, glycolipids, lipoproteins
Virus: ssRNA, dsRNA, unmethylated CpG motifs
Fungus: mannoproteins, phospholipomannan, unmethylated CpG motifs, beta-glucans
Parasite: Profilin, Glycolipids, DNA
Innate Immunity - DAMPs?
Necrosis - nuclear components, extracellular ATP, hsp proteins, uric acid, can be detected.
Extracellular matrix - heparan sulfate, hyaluronan, aggrecan, fibronectin, collagens, fibromodulin.
Role of the innate immune response?
Destroys invade nucleic (viruses) in cytoplasm.
Activates inflammatory pathways + signals for recruitment of immune system cells to sites of damage/infection.
Causes Type 1 interferon for anti-viral defense.
Buys time for the adaptive immune response, promotes and directs the appropriate adaptive immune response.
Adaptive Immunity?
Recognise precise structure → Millions of receptors → Generated by random recombination of gene segments. Antigen-specific receptors on lymphocytes
Adaptive Immunity - T cell receptor?
On T cell surface are 2 protein chains alpha and beta which together make the T cell receptor (TCR), this binds processed antigen fragments presented at cell surfaces. Each antigen receptor binds to a particular site on a antigen - an epitope.
Adaptive Immunity features?
Depends on clonal selection, slow, highly specific to foreign antigens, can form memory, requires priming
Each clone of B cells or T cells has a unique receptor, specific to one antigen; each cell carries many copies of this receptor on the cell surface.
Cells of the adaptive immune system?
Cell of the adaptive immune system - Lymphocyte (agranular leukocyte) 20-40% of circulating WBCs, 99% of the cells in lymph. T-cells + B cells.
Advantages + Disadvantages of the Adaptive Immune System?
Advantages: Massive diversity of receptors, all structures may potentially be recognised. However,because of random nature of receptor generation, there is potential for
autoimmunity.
Disadvantages: Initially very few cells express a specific receptor, so they must be greatly expanded to generate an effective response. This takes time.
Differences between Innate and Adaptive Immunity?
Innate = inbuilt from birth, not enhanced by second exposure to antigens i.e. no memory, uses cellular and soluble components.rapid response, minutes to hours to direct adaptive immunity
Detects conserved microbial structure (PAMP), detect consequences of cell infection or injury (DAMP). Detect missing self molecules on cells - by natural killer cells
