TYPES OF AUTOIMMUNITY AND HYPERSENSITIVITY.pptx

Autoimmunity and hypersensitivity are pivotal components of the immune system's complex interactions, but when they malfunction, they can lead to significant pathological conditions. Autoimmunity refers to the immune system's misguided response, where it erroneously identifies and attacks the body's own tissues as foreign invaders. This self-reactivity can result in chronic inflammation and tissue damage, seen in diseases like rheumatoid arthritis, lupus, and multiple sclerosis. Autoimmune diseases are often categorized into two types: organ-specific, where the immune response targets a specific organ (e.g., Type 1 diabetes), and systemic, where multiple organs are affected (e.g., systemic lupus erythematosus).

Hypersensitivity, on the other hand, involves an exaggerated or inappropriate immune response to external or internal stimuli. It is classified into four types based on the immune mechanisms involved. Type I Hypersensitivity (immediate hypersensitivity) is an IgE-mediated response to allergens, leading to conditions like asthma, hay fever, and anaphylaxis. Type II Hypersensitivity (antibody-mediated) involves IgG or IgM antibodies attacking antigens on cell surfaces, resulting in cytotoxic reactions such as hemolytic anemia or Graves' disease. Type III Hypersensitivity (immune complex-mediated) occurs when immune complexes (antigen-antibody complexes) deposit in tissues, triggering inflammation and tissue damage as seen in conditions like systemic lupus erythematosus and serum sickness. Type IV Hypersensitivity (delayed-type hypersensitivity) is mediated by T-cells rather than antibodies and typically occurs 24-72 hours after exposure to an antigen. This form of hypersensitivity is seen in diseases like contact dermatitis and tuberculosis.

Both autoimmunity and hypersensitivity represent disruptions in the normal immune homeostasis. While they share overlapping mechanisms, they differ in how and why the immune system becomes dysregulated. Autoimmunity stems from a breakdown in self-tolerance, leading to attacks on the body's own cells. Hypersensitivity, meanwhile, arises from an exaggerated response to non-self antigens or harmless substances, or from prolonged exposure that sensitizes the immune system. Understanding the various types of hypersensitivity and autoimmune responses is crucial for diagnosing and managing conditions associated with immune dysfunction. Recent advances in immunology continue to uncover the intricacies of these conditions, offering hope for more targeted therapies and personalized treatment approaches.

1. TYPES OF AUTOIMMUNITY AND HYPERSENSITIVITY SUBMITTED BY – NISHTHA SRIVASTAVA COURSE – B.Sc.(H) MB 4 th semester SUBMITTED TO – Dr. DEEPTI MA’AM

2. CONTENTS

3. AUTOIMMUNITY Autoimmunity refers to a condition in which the body’s immune system mistakenly attacks its own tissues. Normally, the immune system functions to identify and combat foreign individuals such as bacteria, viruses and other pathogens. However, in autoimmune diseases the immune system becomes confused and starts to attack healthy cells and tissues causing inflammation, tissue damage, and various symptoms depending on specific autoimmune condition. There are more than 80 known autoimmune diseases including rheumatoid arthritis, lupus, type 1 diabetes, multiple sclerosis, and inflammatory bowled disease. These conditions can affect almost any part of the body including joints, skin, muscles, blood vessels, and organs.

4. Types of autoimmunity Organ – specific V/S Systemic Primary V/S Secondary Humoral V/S Cell mediated Genetic V/S Acquired Specific Conditions

5. 1. Organ – specific V/s systemic Organ – Specific The immune response is primarily directed against a specific organ or tissues in the body. These autoimmune diseases are characterized by localized damage to specific organs or tissues. Examples; 1. Hashimoto’s thyroiditis 2. Type 1 diabetes 3. Addison’s disease 4. Pernicious anaemia Systemic The autoimmune response affects multiple organs and systems throughout the body. These autoimmune diseases involve widespread inflammation and immune activation, leading to systemic manifestations. Examples; 1. Systemic Lupus erythematosus 2. Rheumatoid arthritis 3. Systemic sclerosis 4. Cryoglobulinemia

6. PRIMARY V/S SECONDARY Primary Autoimmunity It occurs when the immune system directly attacks the body’s own tissues. They often have a strong genetic component meaning that individual may inherit specific genetic factors. Examples; 1. Rheumatoid arthritis 2. Type 1 diabetes 3. Multiple sclerosis Secondary Autoimmunity It occurs when autoimmune diseases develop therefore or complication of another underlying condition, factor, or trigger. These triggers include infections, medications, environmental factors, hormonal imbalances, or other autoimmune diseases. Examples; 1. Autoimmune thyroid diseases 2. Autoimmune hepatitis

7. HUMORAL V/S CELL MEDIATED Humoral Autoimmunity It involves the production of antibodies by B cells, which are a type of WBCs. These autoantibodies can bind to specific antigens present on the surface of cells or in various tissues, leading to inflammation, tissue damage, and dysfunction. Examples; 1. Systemic lupus erythematosus 2. Hashimoto’s thyroiditis 3. Grave’s disease Cell – mediated Autoimmunity It involves the activation of T cells, another type of WBCs, to directly attack and destroy cells or tissues perceived as foreign or abnormal. In CMI, autoreactive T cells recognize self- antigens presented on the surface of body cells as foreign, leading to an immune response against those cells. Examples; 1. Type 1 diabetes 2. Multiple sclerosis

8. Genetic V/s Acquired Genetic autoimmunity It occurs when a person inherits genetic predispositions that increase their susceptibility to developing autoimmune diseases These genetic predispositions can affect various aspects of immune system including the recognition of self vs non-self-antigens and activation of immune responses. Examples 1. Rheumatoid arthritis 2. systemic lupus erythematosus(SLE) Acquired autoimmunity It develops as a result of external factors triggers or events that disrupt immune tolerance and trigger immune responses. These factor can include infections, exposure to environmental toxins, and tissue damage or trauma. Acquired autoimmunity may occur in individual with or without genetic predispositions to autoimmune diseases. Examples 1. Drug induced lupus 2. Autoimmune hepatitis

9. Causes of autoimmunity

10. MECHANISM FOR INDUCTION OF AUTOIMMUNITY

11. HYPERSENSITIVITY Hypersensitivity  (also called  hypersensitivity reaction  or  intolerance ) is an abnormal physiological condition in which there is an undesirable and adverse immune response to antigen. It is an abnormality in the  immune system  that causes immune diseases including allergies and  autoimmunity . It is caused by many types of particles and substances from the external environment or from within the body that are recognized by the immune cells as antigens. The immune reactions are usually referred to as an over-reaction of the immune system and they are often damaging and uncomfortable .

12. TYPES OF HYPERSENSITIVITY REACTIONS

13. EXAMPLES OF HYPERSENSITIVITY Type I hypersensitivity 1. Anaphylaxis Anaphylaxis is our medical emergency as it can lead to acute life - threatening respiratory failure it is an IgE mediated process. It is the most severe form of an allergic reaction where mass cells suddenly release a large amount of histamine and later on leukotrienes. In severe cases intense bronchospasm, laryngeal edema, cyanosis, hypotension, and shock are present. 2. ALLERGIC BRONCHIAL ASTHMA Allergic bronchial asthma is an atopic disease, characterised by bronchospasm. It may also be a chronic inflammatory disease. In its etiology, environmental factors along with a genetic background play an important role. The diagnosis is dependent on history and examination. In allergic bronchial asthma IgE is elevated and sputum eosinophilia is common.

14. type ii hypersensitivity 1. IMMUNE THROMBOCYTOPENIA (ITP) ITP is an autoimmune disorder that occur at any age. Phagocytes destroy sensitized platelets in the peripheral blood. Clinically, it manifests as thrombocytopenia with shortened platelet survival and increased marrow megakaryocytes. Sudden onset of petechiae and bleeding from the gums, nose, bowel, and urinary tract occurs. Bleeding can accompany infections, drug reactions, malignancy, and other autoimmune disorders. 2. AUROIMMUNE HEMOLYTIC ANEMIA (AIHA) There are two types of immune haemolytic anaemia; IgG – mediated (warm AIHA) AND IgM- mediated (cold AIHA). The warm type may be idiopathic autoimmune or secondary to other diseases such as malignancy affecting the lymphoid tissues. The cold type may be idiopathic or secondary to infections such as Epstein – Barr virus. The primary clinical sign of the two is jaundice. 3. MYASTHENIA GRAVIS Myasthenia gravis is an autoimmune disorder caused by antibodies to post – synaptic acetylcholine receptors that interfere with neuromuscular transmission. It is characterized by extreme muscular fatigue, double vision, bilateral ptosis, difficulty swallowing, and weakness in upper arms. Babies born to mothers with myasthenia gravis can have transient muscle weakness due to pathogenic IgG antibodies that cross the placenta.

15. Type iii hypersensitivity 1. SERUM SICKNESS Serum sickness can be induced with massive injections of a foreign antigen. Circulating immune complexes infiltrate the blood vessel walls and tissues, causing an increased vascular permeability and leading to inflammatory process such as vasculitis and arthritis. It was a complication of anti - serum prepared in animals to which some individual produced antibodies to the foreign protein. It was also experienced in treatment with antibiotics such as penicillin. 2. SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) SLE is an autoimmune disease with multi system involvement. The condition is characterised by the presence of circulating IgG and IgM autoantibodies to host tissue components. In most cases, the antibodies are directed against the nucleus, such as double – stranded DNA, histones, and ribonuclear proteins. In some patients, autoantibodies against the cells, including platelets, erythrocytes, neutrophiles, and lymphocytes, can be present. The autoantibodies against the phospholipid moiety of the prothrombin activator complex or cardiolipin can lead to a hypercoagulable state.

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