Haseeb Ullah

  Tolerance Tolerance in the immune system refers to a state where the immune system does not respond to specific antigens (or epitopes) even though it functions normally otherwise. This means that the immune system ignores certain substances as if they were not harmful. Typically, antigens that are present during embryonic development are identified as "self" and do not trigger an immune response. This is because self-reactive T-cell precursors are eliminated in the thymus during fetal development. Antigens encountered later, after the immune system has matured, are considered "NonSelf" and usually provoke an immune response. Although both T cells and B cells are involved in tolerance, T-cell tolerance is more crucial.   T Cell Tolerance Tell tolerance mainly occurs in the thymus during fetal development. This process, known as clonal deletion, involves the destruction of T cells that react against self-antigens (mainly self-major histocompatibility complex [

  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