Establishment of a phagocytic cell line from Bombina orientalis.

Continuous serum-free culture of Bok-2 cells was generated from primary culture of the tail bud stage embryos of the toad, Bombina orientalis. Bok-2 cells can be maintained in modified L-15 serum-free medium prepared by mixing L-15 medium, lactalbumin enzymatic hydrolysate, sucrose and sodium bicarbonate. Bok-2 cells have an ameboid behavior and morphology. When Bok-2 and viable Candida albicans were co-cultured, Bok-2 cells showed an immune response characterized by chemotaxis, phagocytosis and partial clearing activity of Candida cells and colonies. And Bok-2 cells also showed phagocytosis of latex beads without serum treatment and displayed numerous pseudopodia, membrane evagination for phagocytosis and phagosome activity. On the basis of these results, Bok-2 cells were identified as professional phagocytes.