The survival and growth of ovine afferent lymph dendritic cells in culture depends on tumour necrosis factor-α and is enhanced by granulocyte-macrophage colony-stimulating factor but inhibited by interferon-γ

An in vitro culture system is described which allows an analysis of the signals responsible for the survival, growth and functional maturation of afferent lymph dendritic cells (ALDC), a subpopulation of migrating dermal dendritic cells involved in antigen carriage and presentation to T-cells. Purified ALDC survived and grew for up to 30 days in lymph node conditioned medium and survived 14 days in recombinant ovine (rov) TNF-α whereas none were detected after 24 h in rov GM-CSF, rov IFN-γ or rh M-CSF. However, when rov GM-CSF was added to cultures along with rov TNF-α, increased numbers of ALDC compared with input numbers (growth) were recorded on Days 14 and 21. In contrast, when 50–200 units ml−1 of rov IFN-γ were added to cultures of ALDC along with TNF-α or rov TNF-α plus rov GM-CSF, cell survival and growth was inhibited. Antibody blocking studies confirmed the cytokine specificity of these effects. ALDC cultured in rov TNF-α or rov TNF-α plus rov GM-CSF retained MHC Class-II and ov CD-1 antigen expression and accessory function for autologous ov CD-4 T-cell proliferation, although at reduced levels compared with freshly isolated cells. Neither fresh nor cultured ALDC expressed coagulation factor XIIIa.