HK/FDC Cells

Follicular dendritic cell (FDC)-like cell lines (HK cells) from human tonsils were established to investigate the role of FDC in germinal centers of lymphoid follicles. Initially, HK cells expressed markers like CD21, CD23, DRC-1, CD40, VCAM-1, ICAM-1, and HJ2, but lost DRC-1, CD21, and CD23 within three days of culture. Morphologically and functionally, HK cells are distinct from fibroblasts and have unique growth requirements. They bind to B cells, supporting their proliferation, but not to T cells. Activated T cells, stimulated with anti-CD3 antibodies, bind to HK cells, inducing phenotypic changes and promoting their growth. HK cells preferentially bind and stimulate germinal center (GC) B cells, rescuing them from apoptosis. They enhance B cell proliferation in the presence of anti-mu or anti-CD40. These cells also produce soluble factors that contribute to their costimulatory activity. Phenotypic and functional analyses suggest that HK cells may be derived from FDCs, highlighting their potential role in supporting GC B cell maturation and differentiation. Immortalized versions of these HK/FDC-like cells are now also available, offering a more stable and scalable tool for long-term studies of FDC function and B cell interactions.