Eosinophilia. II. Cutaneous eosinophilia in guinea-pigs mediated by passive anaphylaxis with IgGl or reagin, and antigen-antibody complexes; its relation to neutrophils and to mast cells.

More eosinophils accumulate in sites of cutaneous anaphylaxis mediated by homologous IgG1 or reagin, than in skin treated with IgG2, 18 hours after intravenous challenge. The increased number of eosinophils becomes apparent at 4 hours and reaches a maximum at 12–24 hours, whereas neutrophils infiltrate skin sensitized with IgG1 within 15 minutes of challenge and are most numerous at 4–8 hours. There is a much higher ratio of eosinophils to neutrophils in skin passively sensitized with reagin and challenged after 14 or 28 days. In anaphylactic skin, eosinophils accumulate round changed mast cells. The numbers of eosinophils in anaphylactic skin reflect the numbers in the blood when challenged, and no increase in the number of haematogenous eosinophils occurs between the time of challenge and sampling. The behaviour of eosinophils appears to differ from that , in that they, like neutrophils, are attracted more strongly to complexes containing IgG2 than IgG1 antibody. They are also attracted to damaged neutrophils. It is suggested that eosinophils are not selectively attracted to sites of cutaneous anaphylaxis, but enter them with the neutrophils in the relative proportions in which they are present in the blood. They are however selectively retained in anaphylactic, or anaphylactoid tissue, while the neutrophils continue to emigrate.