Attempted induction of an avian eosinophilia using various agents

A series of experiments is described in which attempts were made to produce an avian eosinophilia using various agents. Although none of the experiments was decisive, two demonstrated a slight rise in the eosinophil counts. In one experiment horse serum was injected into a group of fowls on alternate days for 42 days. No eosinophils were seen in any blood smears after this treatment. After a rest period of eight days the birds received further injections for 10 days. The mean eosinophil count rose to over 4 per cent with a range of 1 to 11 per cent. It is considered that this type of response was due to a mild eosinophilia following an eosinopenia. In another experiment a group of fowls were passively immunised with material from a spontaneously occurring eosinophilic bird. Half the birds were placed in cages previously occupied by birds with high eosinophil counts. The other half was housed in another bird room. The results showed that the first group of birds consistently had more than twice the number of circulating eosinophils (3.4 per cent) compared with those of the second group (1.6 per cent). Since this increase appeared to be unrelated to the treatment other causal factors must be considered.