Haseeb Ullah

  Introduction   Immunity: Resistance or defense against harmful agents/substances causing disease.   Immune System: Cells and molecules defending the body against environmental pathogens.   Antigen: Substance stimulating an immune response.   Antibodies: Proteins reacting to antigens.   Self vs NonSelf   Self: Cells, fluids, molecules, and structures from the host.   NonSelf: External substances, living organisms (parasites, fungi), nonliving toxins, or host derived genetic rearrangements.   Types of Immunity   Innate or Natural Immunity: Primary, nonspecific defense present at birth, not altered by repeated exposure.   Acquired or Adaptive Immunity: Specific, acquired through contact with foreign substances, has memory improving response with each encounter.   Innate Immunity   First Line of Defense: Physical barriers like intact skin, mucous membranes.   Second Line of Defense: Cellular components like phagocytic cells, macrophages, NK cells, and hum

  Tolerance and its induction: - Tolerance is the immune system's ability to recognize and tolerate self-antigens. - Induced centrally in the thymus (T cells) and bone marrow (B cells) during development. - Mechanisms include negative selection, receptor editing, anergy, regulatory T cells (Tregs), and immune privilege.   Autoimmune diseases and their factors and mechanisms: - Autoimmune diseases occur when the immune system attacks the body's own tissues. - Factors include genetic predisposition, environmental triggers, and immune dysregulation. - Mechanisms include molecular mimicry, breakdown of tolerance, aberrant lymphocyte activation, and inflammation. - Examples: rheumatoid arthritis, lupus, type 1 diabetes, multiple sclerosis.   Tumor immunity and associated antigens: - Tumors express tumor-specific antigens (TSAs) or tumor-associated antigens (TAAs). - Immune responses target tumors through CTLs, NK cells, and tumor-infiltrating lymphocytes (T