Functional characterization of a swine CD4(+)/CD8(+) double positive lymphoblastoid T-cell line with a CD25(+)/CD45RA(-) phenotype generated in vitrowith interleukin-2

A dual expressing (CD4(+)/CD8(+)) porcine lymphoblastoid T-cell line (pIL-2 d) generated from peripheral blood mononuclear (MN) cells shown to be highl y responsive to exogenous interleukin-2 (IL-2) was characterized. The swine MN cells were initially stimulated with concanavalin A (Con A), and sub-pa ssaged using decreasing amounts of conditioned medium (CM), which was prepa red from culture fluids of Con A activated porcine MN cells, until a steady growth was observed. The resulting pIL-2d cells require exogenous IL-2 fro m CM and are highly responsive to recombinant human IL-2 (rhIL-2). The pIL- 2d cells exhibited a specific, dose-dependent proliferative response to sti mulation with IL-2. The specificity of this proliferative response was conf irmed to be IL-2 induced by its inhibition with an anti-swine IL-2 receptor (alpha -swIL-2R) monoclonal antibody (mAb), Furthermore, the pIL-2d cells are highly responsive to exogenous IL-2 contained in culture fluids derived from antigen-driven blastogenic tests performed with lymphocytes of vaccin ated swine. This property makes the pIL-2d cells an ideal functional adjunc t to immunochemical or molecular tests that are commonly used to measure to tal porcine IL-2. interestingly the phenotype of the pIL-2d cells after fiv e or more passages was shown by flow cytometric analysis to be CD4(+)/ CD8( +)/CD45RA(-)/CD25(+) and to remain unchanged thereafter. Although, the mech anism of selection and maintenance of the CD4(+)/CD8(+) DP cells developed here remains unclear, our data suggest that an oligoclonal or polyclonal ex pansion and maintenance of cells of this phenotype was mediated by exogenou s IL-2. (C) 2001 Published by Elsevier Science B.V.