Dynamics of cytokine production during coccidial infections in chickens: colony‐stimulating factors and interferon

We assayed two classes of immunoregulatory cytokines, colony‐stimulating factors (CSF) and interferon (IFN), during and immediately after a primary coccidial infection in chickens. Coccidial infection induces significant alterations in serum colony‐stimulating activity (CSA) and these alterations immediately precede the characteristic biphasic leukocytosis. CSA rose sharply during the first 24 h post‐inoculation (PI), but returned to control levels by 48 h PL. At this time, we detected an increase in peripheral blood leukocytes which peaked at 96 h PI. A second phase of CSA increase began 96 h PI and peaked at 120–144 h PI which again preceded the second phase of leukocytosis. We also examined the production of IFN during the first 20 days PI. Splenic T cells from Eimeria maxima ‐infected chickens produced significantly less IFN on day 5 PI compared to T cells from the coccidia‐free controls. By days 10 and 15 PI, there was no significant difference in IFN production between the T cells of infected and non‐infected chickens. However, by day 20 PI, IFN production by the T cells of the infected birds produced significantly more IFN than the control T cells. The results of our studies indicated the differential production of two different cytokines by chickens during and following a primary coccidial infection. Based on these experiments, CSF may be some of the first cytokines produced during an E. maxima ‐infection, while IFN may be one of the later cytokines produced.