“…In contrast, patients with Crohn's disease have shown a high incidence of negative Mantoux responses (Blackburn, Hadfield, and Hunt, ,1939;Phear, 1958;Williams, 1965), as well as diminished cutaneous delayed hypersensitivity reactions to dinitrochlorobenzene (Jones, Housley, Ashurst, and Hawkins, 1969). Also the lymphocytes of patients with Crohn's disease have shown low responses to nonspecific mitogens such as phytohaemagglutinin (Walker and Greaves, 1969;Brown, Taub, Present, and Janowitz, 1970;Parent et al, 1971).…”