Establishment of a follicular lymphoma cell line (FLK-1) dependent on follicular dendritic cell-like cell line HK

A novel cell line, FLK-1, was established from bone marrow cells of a patie nt with follicular lymphoma by means of co-culture with follicular dendriti c cell (FDC)-like cell line HK, Immunophenotypic analysis showed that FLK-1 expressed CD10, CD19, CD20, CD38, IgG and HLA-DR, which is a typical featu re of germinal center B cells, Cytogenetic analysis of FLK-1 demonstrated t (14;18)(q32:q21) translocation involving BCL2 and immunoglobulin heavy chai n genes. Especially noteworthy is that the growth of FLK-1 was found to be dependent on a FDC line, HK, When NK cells were removed from the culture, F LK-1 cells stopped growing and eventually died. An apoptotic mechanism appe ared to be involved as indicated by the presence of chromosome condensation and DNA ladder formation. The culture experiment using micropore membranes showed that soluble factor(s) of HK cells supported the growth, while dire ct cell-to-cell contact appeared to be necessary for longterm cell prolifer ation. These findings suggest the importance of the micro-environment for f ollicular lymphoma cells to grow, The FLK-1 cell line may thus prove to be useful for studying the growth mechanism of follicular lymphoma and provide new insights into the pathogenesis of follicular lymphoma.