Delayed-type hypersensitivity reaction in the lungs of guinea pigs due to potassium dichromate.

Potassium dichromate was inhaled by guinea pigs previously immunized by potassium dichromate until strong positive patch tests were obtained. No obvious respiratory changes were noted during and after inhalation. Histologically, however, mononuclear cells infiltrated the interstitial spaces in large areas of the lung, producing considerable thickening of the alveolar spaces in 24 to 48 hr after inhalation. Polymorphonuclear cells were predominant initially. These changes were similar to the delayed-type hypersensitivity reaction in the lung elicited by the inhalation of purified protein derivative (PPD) in the guinea pigs immunized by an injection of dry-killed tubercle bacilli. A less marked reaction was observed in guinea pigs passively sensitized with peritoneal exudate cells and lymph node cells. Consequently, the pulmonary changes were thought to be elicited by delayed-type hypersensitivity reaction due to a simple chemical. The clinical implications of delayed-type hypersensitivity reaction in the lung due to simple chemicals are discussed.