Salmonella enteritidis immune leukocyte-stimulated soluble factors: effects on increased resistance to Salmonella organ invasion in day-old Leghorn chicks.

Cytokines, derived from either concanavalin A-stimulated Salmonella enteritidis-immune chicken T lymphocytes [SE-immune Lymphocyte Stimulated Soluble Factor (LSSF)] or lipopolysaccharide-stimulated SE-immune chicken macrophages [SE-immune Macrophage Stimulated Soluble Factor (MSSF)], were evaluated for their ability to increase resistance to SE organ invasion in day-old Leghorn chicks. In Trial 1, day of hatch chicks were injected i.p. with either SE-immune LSSF or SE-nonimmune LSSF (control). In Trial 2, chicks were similarly injected with either SE-immune MSSF, SE-nonimmune MSSF, or SE-immune LSSF (positive control). Thirty minutes postinjection, all chicks were gavaged with an invasive dose of SE. Twenty-four hours later, livers and spleens from all chicks were cultured for SE. In Trial 1, SE-immune LSSF caused a rapid and marked protection (P < .01) against SE infection as determined by the number of chicks that were culture positive regardless of challenge dose. In Trial 2, SE-immune MSSF was not associated with protection against SE organ infection. These experiments demonstrate that SE-immune LSSF, but not MSSF, are able to confer protection against SE organ invasion in day-old Leghorn chicks. Thus, it appears that the stimulated immune T cell, and not the macrophage, is responsible for producing the soluble products that protected the chicks.