2023 HUB105 Lecture 15 Immune System Problems PDF

Lecture 15 Immune System problems of Clinical Significance BChD I HUB 105 2023 Dept. Medical Biosciences University of the Western Cape Introduction The complexity of the immune response leads to the existence of a variety of clinical condition...

Lecture 15 Immune System problems of Clinical Significance BChD I HUB 105 2023 Dept. Medical Biosciences University of the Western Cape Introduction The complexity of the immune response leads to the existence of a variety of clinical conditions. Immunodeficiency is the failure of the immune system mechanisms in defending against pathogens. Immune system failure results due to a disruption in lymphocyte functioning. Occurs 3 ways: - improper embryological development of lymphoid organs - infection that depresses immune function - treatment or exposure to immunosuppressive agents (radiation/drugs) Immunodeficiency has 2 broad categories: Congenital and Acquired conditions that cause immune cells, phagocytes, or complement to behave abnormally Immunodeficiency diseases Congenital diseases are rare genetic defects and results from improper lymphocyte development. Eg Severe combined immune deficiency (SCID): defective cell- or antibody-mediated immunity, due to low or no B and T cells production. SCID is fatal if untreated; treatment with bone marrow transplants. Acquired diseases develops after birth and causes various diseases from nutritional deficiencies, trauma, stress or viral infection. Eg Acquired immune deficiency syndrome (AIDS) is caused by the human immunodeficiency virus (HIV), that forms its own DNA within the host cell. When this occurs its targets the CD4 T cells (helper), impairing its functioning and depresses cell and antibody mediated response. Impairment of immune system leads to AIDS patients being susceptible to infections, which could lead to death. Hypersensitivity of the immune system Hypersensitivity is an inappropriate or excessive response of the immune system. Two forms Allergies and Autoimmunity Allergy is an excessive immune response or allergic response to a relatively harmless environmental antigen. Antigens that trigger allergic responses are called allergens. An allergic response results after repeated exposure to an allergen. The body becomes sensitized to the allergen and produces IgE (antibodies) IgE is also produced in response to haptens, a partial antigen, that once it binds to body molecules gains antigenic properties and induces an immune response. eg penicillin/preservatives/cosmetics/soaps.  Allergy In an allergic response the IgE antibodies, bind to mast cells and basophils, resulting in a flood of histamine release and inducing the inflammatory response. Allergy symptoms: runny nose, conjunctivitis, urticaria (rash). Eg Hay fever, contact dermatitis Allergic reactions in the mouth Allergic contact reactions due to the metal in brace. http://www.giovannimariagaeta.it/index.php?option=com http://www.capedental.com/2010/allergic-reaction-to-lipgelee-allergic-lip- reaction/ Autoimmune disorders Normally the immune system recognises but ignores self-antigens found in the body. In autoimmune diseases the recognition system malfunctions and the body inappropriately targets itself. It leads to activated B cells making antibodies that target self antigens. The trigger may also lead to reduction in suppressor T cells activity and increase stimulation of helper T cells. Eg Lupus: Chronic disorder affects blood vessels, kidneys, nervous system and skin; symptoms: extreme fatigue, joint swelling, butterfly-shaped rash in the face. Eg Multiple sclerosis: antibodies that normally target proteins associated with measles, influenza or other viruses also attack the myelin sheath of the nerves; symptoms: muscle weakness, spasms, difficulty with balance. Autoimmune disorders By eating away myelin - the protective nerve coating - MS shorts out the flow of information within the brain and between the brain and body, similar to how a stripped electrical wire can short out an appliance. Image © 2009 RelayHealth and/or its affiliates http://healthyhenhousehappenings.blogspot.com/2013/11/day-12- journal-autoimmune-recovery.html  Tissue Transplants The clinical significance of the Major histocompatibility complex (MHC) molecule is realized during an organ transplant. MHC molecules are genetically determined. When MHC molecules present antigens (nonself ) to the lymphocytes this activates an immune response. After organ transplant the T cells are activated by contact with donor MHC molecules on the cell membranes, leading to graft rejection. Eg: Presence or absence of the Rhesus factor (Rh, D antigen form of MHC) in the ABO blood grouping system is important in blood transfusion and During pregnancy, antigens from a Rh- mothers blood and Rh+ foetus can sensitize an immune response in the mother, thus forming antibodies against a future foetus or that foetus eg haemolytic fetalis http://immense- immunology- insight.blogspot.co m/ Revision Questions 1. Define the following: immunodeficiency, congenital disease, acquired disease, allergy, allergen, hypersensitivity, autoimmune 2. What causes the disruption of lymphocyte production, that leads to immune failure? 3. Discuss the difference between SCID and AIDS. 4. Explain what occurs during an allergic resonse. 5. What happens during an autoimmune disease and give an example of this type of disease. 6. Explain the importance of organ transplantation.