Further studies on the role of neutrophils in passive cutaneous anaphylaxis of the guinea-pig.

Passive cutaneous anaphylaxis (PCA) was studied in guinea-pigs sensitized with rabbit antisera to bovine serum albumin or horse spleen ferritin and challenged 4–5 hours later with antigen. Ultrastructural studies of lesions obtained after sensitization or challenge indicated that substantial numbers of neutrophils had infiltrated into the skin. Following challenge these elements exhibited phagocytic activity, presumably representing the uptake of immune precipitates formed in the interstitial spaces. This was associated with degranulative and degenerative phenomena, suggesting that lysosomes were discharged extracellularly. A significant suppression of the intensity of the hyperpermeability response in PCA was noted when animals were pretreated with an antiserum to guinea-pig neutrophils. Antihistamines also suppressed PCA, and the combined effect of neutrophil depletion and antihistamine therapy was additive. It was concluded that a combination of anaphylactic (histamine release) and Arthus-like (neutrophil lysosome release) mechanisms mediated the vascular response in this type of PCA.