DEVELOPMENT OF A MONOCYTE MACROPHAGE-LIKE CELL-LINE, RTS11, FROM RAINBOW-TROUT SPLEEN/

A new rainbow trout cell line, RTS11, arose spontaneously from a long- term haemopoietic culture of spleen. For routine subculture, RTS11 req uires 20-30% fetal bovine serum, a high cell density, and conditioned medium from previous cultures. Through successive passages, RTS11 cult ures maintain a balance between small, non-adherent cells that form th e majority of cells (referred to as round cells) and a few larger, gra nular cells that are either adherent or in suspension surrounded by cl usters of round cells. The large granular cells appear to be macrophag es, and are referred to as macrophagelike cells, because they are phag ocytic, take up DiI-acetylated low density lipoprotein and acridine or ange and stain for non-specific esterase, whereas the round cells appe ar to be at an earlier stage of macrophage development. Medium conditi oned by RTS11 also contains lysozyme-like activity, an additional indi cation that they are of the macrophage lineage. In proliferation assay s, the non-adherent cells are stimulated strongly by RTS11 conditioned medium and by lipopolysaccharide. Rainbow trout head kidney leucocyte s also show a positive proliferative response to RTS11 conditioned med ium. Therefore, RTS11 cells appear to both produce and respond to an a utocrine growth factor(s). (C) 1998 Academic Press.