Effect of dextran-S (α,1-3 dextran) on the growth of plasmacytomas MOPC-104E and J558

The murine plasmacytomas MOPC-104E and J558 secrete IgM-λ and IgA-λ, respectively, which are antibodies to α,1-3 dextran, a constituent of dextran-S (DEX-S) extracted from Leuconostoc mesenteroides. A single i.p. injection of 10 μg DEX-S into BALB/c mice from 7 days before and up to 3 days after the implantation of 5 x 10³ plasmacytoma cells protected the BALB/c mice from developing the tumors. Immunization with other antigens, such as Escherichia coli lipopolysaccharide, inulin (α,1-6 linkage), and dextran T-10 (no known α,1-3 linkages) did not protect the mice from developing the tumors. Growth of LPC-1 was not affected by DEX-S. The mechanism of this growth inhibition is unknown. It does not appear to depend solely on binding of antigen to tumor cells, and the limits of the effective time intervals between antigen and tumor injection suggest dependence on the presence of antibody to a α-1,3 dextran.