Question

Compare and contrast between the four types of hypersensitivity in detail

Answer 1

Answer-

According to the given question-

Hypersensitivity is due to abnormal response of our protective immune system and causing harm to the our body.Several autoimmune disorders, as well as allergy are due to hypersensitivity reactions. Hypersensitivity reactions are divided into four categories.

• Type I hypersensitivity reaction also called immediate allergic reaction
• Type II hypersensitivity reaction also called cytotoxic, due to involvement of antibody which are specific to tissues present in our body, responsible for causing destruction of cells e.g. Goodpasture syndrome
• Type III hypersensitivity reaction are mediated by immune complex-, in this case tissue was damaged due to deposition of antigen-antibody complex e.g. glomerulonephritides
• Type IV hypersensitivity reaction are cell-mediated and occur with the help of sensitized T lymphocytes

Type I hypersensitivity reaction - or Anaphylactic Reaction-there reactions are localized, and occur due to cross-linking of antigen with membrane-bound IgE antibody present on basophill cell or mast cell and causes release of serotonin, Histamine, bradykinin, as well as leukotrienes, prostaglandins, and platelet activating factor during anaphylactic reaction and cause damage of tissue. e.g. Anaphylaxis, Food allergy, environmental allergens such as dust mites,pollen leads to asthma, and atopy.

Type II: Cytotoxic Reaction -it is Antibody-dependent- also a type of cytotoxic reaction, where antibody binds directly to antigen which are already bind to cell membrane and leads to cell lysis by activation of complement system. these reactions are mediated with the help of IgG and IgM antibody. e.g. blood transfusion reaction,Bullous Pemphigoid.

Type III: Immune Complex Reaction -In this type IgG as well as IgM binds with antigen, leads to formation of immune or antigen-antibody complexes, as well as deposition and this causing activation of complement system and attract neutrophils, and leads to chemotaxis and also release enzyme causes tissue damage.e.g., systemic lupus erythematosus and leprosy.

Type IV: Cell-Mediated also called Delayed Hypersensitivity reaction-

This is a Cell-mediated reaction which are initiated with the help of T-lymphocytes or CD4+ T cells and causes release of inflammatory cytokines and mediated with the help of effector T-cells or CD8+ T cells and macrophage, causing interaction between antigens and lymphocytes. After that the sensitized lymphocytes leads to production of cytokines which affect other cell functions . e.g. tuberculosis , Rheumatoid arthritis and Hashimoto's thyroiditis