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. Farmer's lung, which results from repeated inhalation of heat-loving bacteria in mouldy hay, is a well-known example of this condition. Another example is humidifier lung; it occurs when contaminated humidifiers or air conditioners circulate antigens that are capable of causing a hypersensitivity reaction. The mechanisms of this condition are contained within the alveolar.

When the invading soluble antigen is inhaled into the lungs it combines with circulating IgG antibodies. Complexes are formed that precipitate out of the serum and into the tissue of the alveolar membranes. The complexes activate compliment and cause the release of mediators that increase vasodilation and vasopermeability.

The immune complex then in turn binds with the Fc receptors on the mast cells and other leukocytes, this creates the localised inflammation. Activated Fc receptors cause the mast cells to degranulate which causes increased fluid and protein release, bringing about phagocytosis and blood vessel occlusion.

  1. Treatment of extrinsic alveolitis.

The main course of treatment for this condition is to avoid the invading antigen by using respiratory protective face masks which have proved effective in improving symptoms in some cases of the disease. This works due to the fact the circulating antigens are unable to cross through the barrier of the mask into the lungs. In the case of farmers lung by chemically treating hay or sugarcane waste along side good ventilation systems has showed to help to minimize exposure to the antigen. In cases with people who suffer acute attacks of extrinsic allergic alveolitis usually recover quite efficiently without the need for treatment if further contact with the substance is avoided alternatively they can be administered with non steroidal anti inflammatory drugs and paracetamol. In more severe cases treatment is with prednisone. This is a corticosteroid these alleviates the symptoms and aid in the reduction in the severe inflammation. Prolonged or recurring episodes of extrinsic allergic alveolitis may lead to irreversible disease and progressive disability.

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  1. Name some common allergens associated with extrinsic allergic alveolitis and the disease that they cause.

A table to show common allergens associated with extrinsic allergic alveolitis, including 
  the disease and the source (micro-organisms).

A table to show common allergens associated with extrinsic allergic alveolitis, including 
  the disease and the source (animal antigens).

There are also other causes of extrinsic allergic alveolitis which are by chemicals used in paint and fungicide, these antigens cause paint sprayer’s lung and vineyard sprayer’s lung.

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