Induction of IL-15 messenger RNA and protein in human blood-derived dendritic cells: a role for IL-15 in attraction of T cells.
IL-15 is a pleiotropic cytokine with IL-2-like functions. As IL-15 was shown to be mitogenic for T cells, we wondered whether human blood-derived dendritic cells (DC), as the primary stimulators of T cell responses, are able to produce IL-15. To test our hypothesis, DC were grown under serum-free conditions from human peripheral blood using granulocyte-macrophage CSF and IL-4. Cultures were assayed for IL-15 mRNA production at various times by semiquantitative reverse transcription-PCR. Low baseline signals were detected from days 0 to 5 of culture. A significant increase was detected from days 5 to 9 of the culture. When DC were further enriched by immunomagnetic beads to >98% purity as determined by CD83 staining, IL-15 mRNA signals were exclusively found in the CD83+ fraction. This increase in mRNA signals was paralleled by IL-15 protein release from days 9 to 12 as detected by CTLL-2 assay and ELISA. In addition, protein levels were increased >10-fold by adding paramagnetic beads to the cultures, thereby inducing phagocytic activity. Furthermore, DC supernatants were tested for chemokinetic and chemotactic activities for T cells in a checkerboard filter assay. It was shown that supernatants express chemokinetic and chemotactic activity for T cells. This activity was blocked almost completely by addition of an anti-IL-15 mAb. Our data show that human blood DC contain IL-15 mRNA and produce functional protein that is induced in culture. Protein release is triggered by phagocytic activity. Furthermore, DC-derived IL-15 has chemotactic and chemokinetic activities for T cells, suggesting a role for IL-15 as an attractant of T cells during the initial DC/T cell interaction.
Jonuleit
H
H
Department of Dermatology, University of Mainz, Germany.
Wiedemann
K
K
Müller
G
G
Degwert
J
J
Hoppe
U
U
Knop
J
J
Enk
A H
AH
D002478:Cells, Cultured; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000276:immunology*; D003713:Dendritic Cells / Q000378:metabolism*; D006801:Humans; D018189:Immunomagnetic Separation; D019409:Interleukin-15 / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics / Q000502:physiology*; D010587:Phagocytosis; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000097:blood*; D013601:T-Lymphocytes / Q000276:immunology*
D019409:Interleukin-15; D012333:RNA, Messenger