Low affinity binding of mouse immunoglobulin to human CD5+ B cells.
Polyreactive immunoglobulin (Ig) secreted by CD5-bearing B cells has the capacity to bind a broad range of self and foreign antigens. Flow cytometric analysis was used to detect low-affinity binding of mouse Ig molecules to the surface of CD5-bearing B cells from patients with chronic lymphocytic leukaemia (CLL). Mouse Ig isotypes G, A, and M, and IgG subclasses G1, G2a, and G3 bound to the B cell surface via a mechanism not involving the antigen-binding site of the mouse Ig molecule. Fab and F(ab')2 fragments of mouse Ig associated with the CLL cells in a similar manner to intact Ig, indicating that Fc receptor interactions were not involved. Dissociation of the mouse Ig from the B cell surface by three washing steps distinguished this lower-affinity binding from high-affinity binding which occurs through the antigen-binding site of a mouse monoclonal antibody (MoAb) when it recognizes a specific cell surface epitope. Blocking studies suggest that the low-affinity binding occurred via surface IgM and surface IgD (sIgM/sIgD) on the CD5-bearing B cells. The results are consistent with the expression of polyreactive Ig on the surface of CD5-bearing B cells in CLL.
Weston
K M
KM
Immunobiology Unit, University of Technology, Sydney, NSW, Australia.
Raison
R L
RL
D000818:Animals; D015703:Antigens, CD; D001402:B-Lymphocytes / Q000276:immunology*; D001665:Binding Sites; D001667:Binding, Competitive; D018956:CD5 Antigens; D002460:Cell Line; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000276:immunology; D051379:Mice
D015703:Antigens, CD; D018956:CD5 Antigens; D007136:Immunoglobulins