Answer: Diseases where the immune system attacks the body's own tissues.
- A Diseases caused entirely by invading external bacterial or viral pathogens from outside the body
- B Diseases where the immune system attacks the body's own tissues
- C Genetic diseases that are inherited directly from one or both biological parents
- D Diseases resulting from a congenital deficiency in the total number of immune cells
Correct answer: B. Diseases where the immune system attacks the body's own tissues
Explanation: Autoimmune diseases occur when self-tolerance breaks down and the immune system attacks self-antigens. Examples: Type 1 diabetes (attack on pancreatic beta cells), Rheumatoid arthritis (attack on joint synovium), Systemic lupus erythematosus (anti-nuclear antibodies), Multiple sclerosis (attack on myelin).
An antibody is Y-shaped, with two identical antigen-binding sites at the tips of the variable regions - each shaped to recognise one specific antigen - while the constant (Fc) region at the base is recognised by immune cells to trigger further responses.
Concept context
Innate and adaptive immunity, B cells, T cells, antibodies, vaccines, and immune disorders. Critical for NEET.