The mechanism of SiO2 (Aerosil)-mediated enhancement of the proliferative response of mouse spleen lymphocytes to antigen and mitogens in a serum-free system.

SiO2 particles enhanced the in vitro proliferation of splenic B cells obtained from BALB/c mice immunized with sheep erythrocytes. T cells from immunized animals were capable of replacing SiO2 with regard to the enhancement of both in vitro proliferation and the primary immune response. In addition, the stimulating effect of IgG, phytohemagglutinin (PHA) and concanavalin A (Con A) on spleen lymphocytes was also augmented by SiO2. The enhancing effect of SiO2 was higher at suboptimal than at supraoptimal concentrations of Con A. SiO2 is capable of binding Con A. The SiO2-bound lectin retained its mitogenic effect on spleen cells and, under certain conditions, SiO2-bound Con A was considerably more active in this respect than the free substance.