Department of Pathology, Room L-1037, 263 Farmington Avenue, Farmington, CT 06030-3105, USA. rajan@neuron.uchc.edu <rajan@neuron.uchc.edu>
Gell and Coombs classified hypersensitivity reactions into four 'types'. I suggest that the premise that these reactions represent 'hypersensitivity' manifestations is limiting and that they represent four major strategies that the body uses to combat infectious agents. I further propose that there is a fifth strategy that was not envisioned in the Gell and Coombs classification.