Discussion
A patient with tuberculosis shows a positive Mantoux test after 48 hours. Which cells primarily mediate this response ?
Answer: C
The response is mediated mainly by CD4+ Th1 cells (printed in the paper as 'Thl').
The Mantoux (tuberculin) test is a type IV, delayed-type hypersensitivity reaction. Sensitised CD4+ Th1 cells recognise the tuberculin antigen and release interferon-gamma and other cytokines. These recruit and activate macrophages, causing induration that peaks at 48-72 hours.
B-lymphocytes and plasma cells make antibodies, which drive type II and III reactions. Mast cells cause immediate type I reactions within minutes. None of these explains a delayed, cell-mediated response.
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