1. Intro to Immunology Flashcards
List some innate nonspecialised anatomical and functional defences.
What are the 2 specialised defenses?
Intact skin, muco-ciliary escalator, cough reflex, complete emptying of bladder, pH of stomach and vagina, GI tract flora/vagina/skin etc., bile, sebum
Innate specialised and adaptive specialised immune systems
Describe the innate specialised immune system.
Describe the adaptive specialised immune system.
Cells: neutrophils, macrophages, eosinophils, mast cells, basophils, NK cells
Molecules: lysozyme, complement, lectins
The whole inflammatory response with its mediators: histamine, leukotrienes, prostaglandins, platelet activating factor etc.
The lymphocytes: B (with their antibody) and T
Immune response = activation of some of these cells and molecules
What is an immunogen?
What is an antigen?
What is a determinant?
Anything that provokes an immune response
Anything that is recognised by cells and molecules of the immune response
The bit of an antigen that is recognised by the agents of the immune system via receptors (molecule/complex of molecules which posess at least one recognition site)
Recognition site binds to determinant b/c of the fit between their 3D shapes and the electrostatic and VDW forces.
Distinguish between high and low specificity.
List some antigen receptors.
Give an example of how the immune system uses receptors to interact with other components of itself.
Distinguish between self and non-self.
If receptor is of high specificity it will only bind to one exact kind of determinant. If it’s of low specificity it will also bind to slightly different determinants.
Ab, T-cell receptora, toll-like receptors, collectins on phagocytes all interact with determinants on antigens
Fc receptors on phagocytes interact with Fc portion of Ab
Self = all determinants on molecules manufactured by an individual, encoded by the individual’s genes, or manufactured by that individuals enzymes. Non-self = any determinant not part of self.
How is nonself/self discrimination mediated?
How is damage/not damaged discrimination mediated?
How can the immune system destroy nonself?
By antigen receptors of various degrees of specificity.
Receptor-mediated, internal (damaged cell may detect own damage and respond (pause mitosis/apoptosis/signal the damage) or exernal (cells of innate immune system recognise it via toll-like receptors etc.)
Enzymes, phagocytic cells using enzymes, oxidising agents, free radicals etc. internally, agents that make pores in cell membranes etc. May have to destroy self cells to destroy pathogens within, but LOCALISED.
What is tolerance?
What is memory?
Specific non-reactivity to a potentially antigenic substance (e.g. food). The immune system should be tolerant of self, and of certain substances.
Enhanced specific immune response that follows repeated exposure to an antigen. Depends on expansion of specific clones of lymphocytes.
Describe the 5 free molecules of innate specialised immunity.
1) Lysozyme: enzyme in body fluids and secretions specific for NAM-NAG link
2) CRP: binds some bacteria and dead cells via phosphocholine
3) Lectins: specific for mannose etc. plentiful on bacteria. Mannose-binding lectin free in plasma and lymph
4) Complement: system of proteins in blood/lymph that can activate each other. Alternative pathway: initiated by cells that lack self determinants, or posses particular strange determinants
5) Defensins and cryptocidins: secreted by epithelial cells and phagocytes, disrupt bacterial membranes and cell walls but harmless to self cell membranes
Describe the 2 different categories of phagocytic receptors of innate specialised immunity.
Describe the 4 phagocytic cells of innate specialised immunity.
Cell antigen receptors: toll-like, lectins. A variety of these, but same selection on each phagocyte
Cooperation: Fc (with Ab), C3b (with complement)
1) Neutrophils: neutrophilic polymorphonuclear leucocytes, shortlived (days) phagocytes, innate antigen receptors and cooperation receptors
2) Monocytes/macrophages: become macrophages in tissues, longlived phagocytes (helped by cooperation with CD4 T-lymphocytes), innate and cooperation receptors
3) Eosinophils: eosinophilic polymorphonuclear leucocutes, phagocytes specialised to combat helminths, innate and cooperation receptors
4) Dendritic cells: similar to monocytes but specially designed to initiate T-lymphocyte activation
Describe the ‘alarm cells’ of innate specialised immunity.
What are the ‘null lymphocytes’?
Describe cytokines and mediators.
Mast cells and basophils (basophilic polymorphonuclear leucocoytes), common around skin, mucosa, BVs, cooperation with complement, nerves, Ab (Fc and IgE), release inflammatory mediators on activation. Initiate inflammation.
NK cells (killer and natural killer activity)
Important messenger molecules, not specific for antigen, don’t bind antigen, need cooperation receptor to deliver message to
Describe the 2 components of the adaptive specialised immune system.
Lymphocytes.
1) B-lymphocytes: synthesise and express Ab, may become plasma cells (which secrete Ab). Mature in bone marrow. Antigen receptor is Ab. Recognises antigen anywhere. Plasma cells can secrete receptor.
2) T-lymphocytes: CD4 +ve (helper T-lymphocytes), CD8 +ve (cytotoxic T-lymphocytes). Mature in thymus. Antigen receptor is not Ab. Recognition of antigen only when presented on surface of another cell. Little/no secretion of receptor.
How are antigen receptors distributed among lymphocytes?
How is self-tolerance preserved?
Variety of antigen receptors, all the same on any one lymphocyte, big range on all the different lymphocytes, clonally distributed, receptor genes mutated in chance process. Memory = expansion of clone after antigen encounter
Deleting autoreactive cells soon after formation.
Describe clonal deletion.
Describe clonal expansion and immunological memory
What is the antigen receptor on T-lymphocytes and B-lymphocytes?
How must a T-lymphocyte see an antigen?
What happens when a B-lymphocyte becomes activated?
What do CD4 an CD8 T-lymphocytes do?
What do antibodies do?
T-lymph: T-cell receptor. B-lymph: Antibody
Presented by other cells. Important that dendritic cells present antigen in first activation.
Becomes plasma cell and secretes Ab
CD4: helpers, secrete cytokines to help activate B-lymphocytes and macrophages.
CD8: kill infected self cells
Many specificies, specific for antigens, block pathogen binding, cooperation with complement and phagocytes
What are the cells of the defence system derived from?
Pluripotent bone marrow stem cell via myeloid (GEMM) and lymphoid linage.
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