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Intradermal injection of phytohemagglutinin (PHA) in the wattles of chickens elicited marked swellings often accompanied by induration. Histologically, this reaction was characterized by a perivascular accumulation of lymphocytes and macrophage migration in the central layer of the wattles. Heterophilic infiltration was observed mostly at early hours and waned thereafter. Sometime basophils were prominently located around the vessels. These responses were significantly decreased in cases of neonatal thymectomy. Therefore, the PHA skin test was considered to be a thymus-dependent response. The use of the PHA skin test in chickens may provide useful information for the evaluation of thymus-dependent function.
Goto et al. (Sun,) studied this question.