Serum-free Culture of Hamster Lymphoid Cells and Differential Inhibition of Lipopolysaccharide Stimulation by Isologous Serum

The optimal conditions for serum-free cultures of hamster lymphoid cells were determined. The cells responded to both the nonspecific thymus-derived lymphocyte mitogen concanavalin A (Con A) and the nonspecific bone marrow-derived lymphocyte mitogens lipopolysaccharide (LPS) and dextran sulfate (DxS). Normal MHA hamster serum was shown to specifically inhibit the response to LPS and DxS by 95% without inhibiting the response to Con A. The serum also did not inhibit one-way mixed lymphocyte reaction. Incubation of cells in 5% serum for short periods of time, followed by serum-free culture, did not lead to inhibition. The serum inhibited the LPS response by 65% even when added 24 h after initiation of the culture. The activity was associated with the high-molecular-weight material on Sephadex G-200 fractionation of serum. The inhibitory fraction did not possess antibody activity to LPS. The possibility that the material is an alpha2-macroglobulin is discussed.