INHIBITION OF THE IN-VITRO DEVELOPMENT OF EIMERIA-TENELLA IN CHICK KIDNEY-CELLS BY IMMUNE CHICKEN SPLENOCYTES

An invitro microbicidal assay was used to study the immune response of chickens to Eimeria tenella by measuring the effect of splenocytes fr om immunized chickens on intracellular development of E. tenella. Sple nocytes were prepared from specific-pathogen-free chickens [strain P2a (B19B19) or N2a(B21B21)], immunized one, two, or three times with non- lethal doses of E. tenella. Twelve hours following infection of chick kidney cells (CKCs) with E. tenella sporozoites, splenocytes were adde d to infected CKCs for 4, 8, or 36 hours. Intracellular E. tenella dev elopment was allowed to continue until 72 hours after sporozoite infec tion, when intracellular development was quantitated by counting meroz oites. Immune splenocytes significantly inhibited E. tenella intracell ular development after one, two, or three immunizations. Significant i nhibition occurred with 4, 8, or 36 hours of co-culture and was no gre ater with longer co-culture times. Immune P2a splenocytes significantl y reduced merozoite development in both syngeneic P2a and allogeneic N 2a infected CKCs, whereas immune N2a splenocytes had little effect on E. tenella development in either N2a or P2a infected CKCs. These resul ts suggest that immune splenocytes are induced and act relatively rapi dly and are not apparently restricted by the major histocompatibility complex, consistent with natural killer cell activity.