<prompt> Delayed hypersensitivity involves:NeutrophilsMonocytesEosinophilsLymphocytes  <response>: Ans. is d i.e., Lymphocytes Ref: Ananthanarayan, 9the, p. 167 and 8the, p. 168 Reaction is mediated by sensitized T-lymphocytes which, on contact with specific antigen, release lymphokines that cause biological effects on macrophages, leucocytes and tissue cells. Delayed type by CD4 Th1 cell. 