An immunological basis for the anaemia of acute Salmonella gallinarum infection of chicken. II. The relationship of the immune response to the development of the haemolytic anaemia.

The ability of chickens to respond immunologically during acute infection has been examined in relation to the underlying mechanism of the associated haemolytic anaemia. In spite of the severity and acuteness of the experimental infection, the majority of the chickens showed a marked immune response to lipopolysaccharide (LPS) derived from the challenge organism. Peak antibody titres occurred 5–6 days after infection, coincidentally with erythrocyte modification and with maximum destruction of erythrocytes. However, those animals which died of the per-acute form of the disease (within 3 days of challenge) showed neither antibody response, nor erythrocyte modification, and did not develop anaemia. It was also observed that erythrocytes which were positive to the direct Coombs test persisted in the circulation of surviving chickens for comparatively long periods (on average 4 days). The evidence is consistent with the hypothesis that an immunologically-mediated mechanism may be responsible for the development of the anaemia.