Resistance to Salmonella enteritidis organ invasion in day-old turkeys and chickens by transformed T-cell line-produced lymphokines.
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We previously reported an increased resistance to Salmonella enteritidis (SE) organ invasion in chicks and turkey poults injected prophylactically with SE-immune lymphokines (ILK). In the present study, concanavalin A (Con-A)-activated splenic T cells isolated from SE-hyperimmunized hens were transformed in vitro with reticuloendotheliosis virus strain T (REV-T) (chicken syncitial virus). These transformed T cells were then maintained as a long-term (> 1 yr) cell line for the harvest of immune lymphokines (VILK). The efficacy of VILK to protect turkey poults and chicks against SE organ invasion and the correlation between organ invasion and peripheral blood heterophilia were then evaluated. Three groups of day-old poults and chicks were injected intraperitoneally with either phosphate-buffered saline (PBS; group A), ILK (group B), or VILK (group C). Thirty minutes postinjection, poults and chicks were challenged per os with 5 x 10(5) colony-forming units (CFU) SE and 5 x 10(4) CFU SE, respectively. At 24 hr posttreatment, birds in groups A, B, and C were euthanatized and liver samples were cultured for the presence of SE. Both the VILK- and ILK-treated turkeys and chicks had significant reductions in organ invasion when compared with the PBS-injected controls (P < 0.005). For peripheral blood studies, turkeys and chicks were treated as above, and at 4 hr post-PBS, ILK, or VILK injection; total and differential peripheral blood counts were performed on birds from each group. A significant (P < 0.05) peripheral blood heterophilia at 4 hr postinjection was observed in the ILK- and VILK-treated birds, with no such increase found in the PBS-injected group. Correlation analysis revealed a direct relationship between the peripheral blood heterophilia in turkeys and chicks seen at 4 hr postinjection and the reduction in SE organ invasion seen in the VILK and ILK treatment groups (r = 0.991, r = 0.91, respectively). T cells isolated and transformed from nonimmune chickens did not produce factors that protected chicks from SE organ invasion and did not cause the peripheral blood heterophilia observed with ILK and VILK. These results show that the virally transformed SE-immune T-cell line produces lymphokines that result in the same level of peripheral blood heterophilia as ILK and was equally protective against SE organ invasion as ILK.
