| Abstract: | A comparative study of B cells present in human bone marrow and blood was performed. In both compartments the cells carrying the Ig receptors were found to be small mononuclear cells. Predominance of IgM receptors was found on bone marrow cells whereas Ig receptors present on peripheral blood cells were predominantly of the IgG class. Bone marrow lymphoid cells of non-sensitized donors were capable of binding a primary antigen, keyhole limpet haemocyanin (KLH) and could be retained on glass bead columns coated with either KLH or with goat anti-human IgM antiserum but not with anti-IgG. Whereas bone marrow cells of donors immunized with KLH 16–27 days earlier lacked KLH reactive cells, the latter cells could be demonstrated in the blood. It is concluded that human bone marrow B cells carrying IgM receptors are essential for the early antigen recognition step following which recruitment of these cells into the circulation takes place. |
