Effect of sinomenine on antibody responses in mice.

Sinomenine, an epimorphinan alkaloid, was tested for the immunosuppressive effect in mice. This compound produced a decrease of plaque-forming cells (PFC) to a T cell-dependent antigen, sheep red blood cells, in vivo. The depression of the PFC response induced with sinomenine was dose and time dependent. On the other hand, it failed to suppress the PFC response to a T cell-independent antigen, lipopolysaccharide. The immunosuppressive dose of sinomenine did not alter the cellularity of spleen, thymus, bone marrow and peripheral blood leucocytes, the DNA synthesis activity of bone marrow cells nor the proliferative responses of spleen cells induced by T cell and B cell mitogens in unprimed mice. These data suggest a selective effect of sinomenine on lymphoid cells. This compound has a potential for use in studies of immuno-deficiencies or clarifying some aspect of immunity.