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Case studies.Extrinsic Allergic Alveolitis (Type III hypersensitivity) ANDSevere Combined Immunodeficiency (SCID)

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Clinical Immunology CH0054 Case studies. Extrinsic Allergic Alveolitis (Type III hypersensitivity) & Severe Combined Immunodeficiency (SCID). Barry Hollinshead Biomedical Sciences Bsc Second Year. Introduction. As part of my clinical immunology module I have been given two case studies in which I am to answer questions set on each case. The first case is extrinsic allergic alveolitis type III hypersensitivity. This complex condition caused by repeated inhalation of certain different antigens is an immunological triggered disease in where certain antigens provoke inflammation in the distal airways and especially the alveoli in susceptible individuals. The second case study refers to SCID which is severe combined immunodeficiency. First named more than 20yrs ago and it is severe because it often proves fatal before the patients reaches the age of 2 if it is unrecognised. The defect is in both the humoral and cell mediated immunity hence combined. Case study 1. Extrinsic Allergic Alveolitis (Type III hypersensitivity) 1. The basic immunological mechanisms of extrinsic allergic alveolitis. There are many types of dust that cause an allergic reaction in the lungs. The organic dusts contain micro-organisms, proteins and chemicals that cause extrinsic allergic alveolitis. ...read more.


As a result of these recurrent infections patients can die before the first year of life. There are many different causes of SCID and all of them are inherited either by X linked inheritance or autosomal recessive inheritance. X linked cause of SCID. The main and most common cause of this disorder is the X linked form known as SCID - X1. This is caused from mutations in one of the genes on the X chromosome known as the IL2RG. It is this gene which is responsible for creating the component of the receptor which lies on the surface of a lymphocyte that transmit information to the lymphocytes to mature and fight infection activated by chemical messengers called cytokines. The area of the lymphocyte receptor that has the defect is in the "common" gamma chain (?). This is an important component for the mobilisation of the immune systems defences for the fight against infection. The ? chain is a component of the lymphocyte receptors for several cytokines and the interleukin-2 (IL-2) receptor. Defects in the ? chain of the IL-2 receptors result in an absence of the T- and natural killer cell maturation; although the B- lymphocyte count may be normal, despite this there function is very poor. ...read more.


gamma chains the receptor has a much higher affinity for the IL-2. This causes the IL-2 receptor to respond to much lower concentrations of IL-2. It is when binding to the high affinity receptor the progression through the rest of the cycle is triggered. The function of the IL-2 receptor is to attract the IL-2 to the T- cell to activate the cell to divide rapidly to produce armed effector T-cells. Fig. 2. Shows the high affinity IL-2 receptor with all three chains produced on an activated T-cell with the IL-2 binding to the cell. 3. Describe the treatment of T- B + SCID- X1. The first approach would be to treat and control any current infections by placing the patient in a sterile environment. One way this is done is by using an isolator crib"bubble". The child would be kept free from any possible infections but as the child grew the bubble would have to grow. However the most effective treatment would be a bone marrow transplant with a compatible donor. The stem cells in the bone marrow live for a long period as they can renew themselves when they are needed to and they produce a continuous supply of healthy immune cells. Transplants that are performed in within the first three months of life have the highest success rate. Barry Hollinshead. ...read more.

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