Development of follicular dendritic cells: a study using short-term bone marrow cell grafting in SCID mice

To evaluate the cellular origin of follicular dendritic cells (FDC) in lymphoid follicles (LFs), severe combined immunodeficient (SCID) mice (H-2d) were grafted with 5-bromo-2'-deoxyuridine (BrdU)-incorporated bone marrow cells from CB-17 mice (H-2d) and with non-BrdU-incorporated bone marrow cells from C3H mice (H-2k) and Wistar rats (RT1u). This procedure was followed by antigenic stimulation with horseradish peroxidase and related immune complex (mouse peroxidase anti-peroxidase) administration. Secondary LFs in the lymph nodes and spleen of the reconstructed SCID mice were examined morphologically and immunocytochemically. LFs reconstructed with CB-17 mouse bone marrow cells contained FDCs capable of trapping and/or retaining mouse peroxidase anti-peroxidase as immune complexes. Secondary LFs contained BrdU-incorporated germinal center lymphocytes but not non-lymphoid stromal cells. A cell grafting study in SCID mice using bone marrow cells from C3H mice and Wistar rats demonstrated that FDCs in reconstructed LFs exhibited a marker specific for the recipient but not for the donor. These data indicate that functionally active FDCs occur de novo in reconstructed LFs in SCID mice, and do not support the view that FDCs originate from bone marrow cells in short-term reconstructed LFs.