Pathology of reversed passive Arthus reaction in the chicken.

Sequential study of gross and microscopic changes in the chicken skin revealed that it was possible to induce a reversed passive Arthus reaction in 14- to 20-week-old chickens, using bovine serum albumin and anti-bovine serum albumin. However, high doses of immune reactants were required to elicit lesions of optimal intensity. The lesions were characterised by erythema, oedema, and the formation of thrombi in the vessels of the superficial dermis. Thrombosis, caused by the adherence of thrombocytes to vascular endothelium, induced widespread necrosis and haemorrhage. The inflammatory changes, which were confined to the deep dermis, included a necrotising vasculitis with infiltration of heterophils, monocytes and basophils. Phagocytosis of carbon particles by heterophils and basophils appeared to be sensitisation-dependent. The reaction was also characterised by the development of perivascular lymphoid foci. The findings indicate that in chickens the thrombocyte appears to be the principal cell involved in the induction of tissue damage.