Innate and Adaptive Immune System Overview PDF

The immune system overview The body’s defences Innate immunity Cellular and chemical response that blocks microbial invasion and minimises tissue damage. Activates immediately, ideally lasts a short time and eliminates the pathogen. Recognition relies on the differences between invaders...

The immune system overview The body’s defences Innate immunity Cellular and chemical response that blocks microbial invasion and minimises tissue damage. Activates immediately, ideally lasts a short time and eliminates the pathogen. Recognition relies on the differences between invaders and the normal tissue. Molecules that kill invaders, molecules that recruit cells and kills invaders. in Inflammation is part of the innate immune system Adaptive immunity Recognises and destroys invaders and learns from the process Next time response is more effective Also called the acquired immune system. Takes time to become effective Key difference Lies in the use of cell surface receptors to recognise invaders Cells of the innate IS use a limited number of preformed receptors that bind molecules commonly expressed on many different microbes Cells of the Adaptive IS generate enormous numbers of new and unique receptors Types OF INVADERS Potential invaders include bacteria, viruses, helminths (worms) Divided into two broad categories Those that reside outside cells - extracellular invaders ○ Most bacteria, fungi, protozoa and helminths Those that originate or live in cells of the body - intracellular invaders ○ Viruses, intracellular bacteria and protozoa These require different defensive strategies Humoral is The humoral IS involves soluble proteins called antibodies that target invaders. Antibodies are found in body fluids (humours) This branch of the IS targets extracellular invaders. Antibody-mediated response – proteins in the blood. Antibody-mediated IMMUNE RESPONSE These immunity providing substances are proteins called antibodies Antibodies (Ab) form part of the adaptive immune response They are produced in response to an antigen Antigen (Ag) - a foreign substance that can trigger an immune response Abs are specific to Ag and can bind to them. Response is quicker and lasts longer The antibodies produced after repeated exposure are able to bind and neutralise antigen better than those produced earlier in the immune response. This is the basis of Vaccination (Increased response is not indefinite) Cell-mediated iS In cell-mediated response specialised cells target infected or abnormal cells. This branch of the IS targets intracellular or endogenous invaders. Foreign cells are recognised by the IS and destroyed. This is the basis of tissue graft rejection. Second graft from same donor Response is quicker and more intense CELL-MEDIATED IMMUNE RESPONSES What is recognised as foreign? Tissue grafts from another animal ○ Even if it’s the same tissue Cells with slight changes ○ Aged cells ○ Virus infected cells ○ Cancer cells Cells that are seen as foreign are recognised specifically and cells called lymphocytes target them for destruction. Mechanisms of Adaptive immunity Antigen must be trapped, processed and recognised as foreign. Information must be conveyed to antibody producing system or cell mediated IS. Antigen must be eliminated Antigen must be remembered so that next exposure to it results in a quicker and more efficient response.