Functional characterization of equine dendritic cells propagated ex vivo using recombinant human GM-CSF and recombinant equine IL-4

Naive T cells can be activated both in vivo and in vitro by specialized ant igen presenting cells, dendritic cells (DC), with potent antigen-specific, immunostimulatory activity. Indeed, DC can provide an extremely powerful an d important immunological tool by which to potentiate the immune response f or specific recognition of foreign antigens. Until recently, the direct iso lation of DC from PBMC required laborious procedures with extremely poor yi elds (<0.1%). Methods have been developed for the human, lower primate, and murine model systems to propagate large numbers of DC from PBMC or bone ma rrow ex vivo with various cytokines. However, all other model systems, incl uding equine, still require the laborious isolation procedures to obtain DC . In this study, we have adapted the methods developed for the human system to generate large numbers of equine DC from PBMC precursors using recombin ant human GM-CSF and recombinant equine IL-4. Our report is the first docum entation of ex vivo generated DC from PBMC in a domesticated animal model s ystem. Equine DC derived from PBMC were rigorously characterized by analyzi ng morphological, phenotypic, and functional properties and were determined to have similar attributes as DC generated from human PBMC. Equine DC appe ared stellate with large projectiles and veils and had cell surface antigen s at similar levels as those defined on human and murine DC. Furthermore, f unctional attributes of the DC included rapidly capturing antigens by pinoc ytosis, receptor-mediated endocytosis, and phagocytosis, activating naive T cells in a mixed leukocyte reaction to a much greater extent than macropha ge or lymphoblasts, presenting soluble and particulate antigen 10-100 fold more effectively to T cells on a per cell basis than macrophage or lymphobl asts, and presenting soluble and particulate antigen to both CD4+ and CD8T cells. Taken together, our study provides a framework by which equine DC can now be readily produced from PBMC precursors and presents an impetus fo r and model by which DC can be simply generated in other animal model syste ms. (C) 1999 Elsevier Science B.V. All rights reserved.