Answer: Humoral immunity involves B cells and antibodies (against extracellular pathogens); cell-mediated immunity involves T cells and kills infected cells directly.
- A Both forms of immunity are sometimes mistakenly thought to be functionally identical and to operate through the same mechanism as widely reported in standard practice
- B Humoral immunity involves B cells and antibodies (against extracellular pathogens); cell-mediated immunity involves T cells and kills infected cells directly
- C Humoral immunity is sometimes thought to act much faster than cell-mediated immunity in most clinical cases under most conditions encountered as frequently observed in practice
- D Cell-mediated immunity is sometimes mistakenly described as carried out by B cells, with humoral immunity carried out by T cells in many documented cases
Correct answer: B. Humoral immunity involves B cells and antibodies (against extracellular pathogens); cell-mediated immunity involves T cells and kills infected cells directly
Explanation: Humoral immunity: B cells produce antibodies that target extracellular pathogens (bacteria in blood, viruses before they enter cells). Cell-mediated immunity: cytotoxic T cells (CD8<sup>+</sup>) directly kill infected host cells displaying pathogen antigens on MHC I.
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.