The nature of retest reaction in delayed hypersensitivity. I. Light microscopic changes in the skin of the eyelid.

The retest reaction is a variant of delayed hypersensitivity where in repeated application of an antigen at the same site leads to an intense eosinophil leucocytic infiltration. This reaction has been produced experimentally for the first time in the eyelids of rabbits and guinea-pigs and it is possible that such a mechanism is implicated in a variety of clinical ocular conditions in which IgE does not appear to feature. It was also found that tissue reaction was modified in the absence of suppressor cells, these having been temporarily inhibited by pretreatment of the animals with cyclophosphamide.