Effect of neuraminidase on the stimulatory capacity of cells in human mixed lymphocyte cultures.

Treatment of the stimulatory cells in human one-way mixed lymphocyte cultures with neuraminidase (VCN) caused a marked increase in their stimulatory capacity as measured by an increase in DNA-synthesis by the responding cells. No effect was observed by treating the responding cells with VCN. Heatinactivation of VCN, or incubation in the presence of its specific substrate, N-acetylneuraminlactose, prevented the stimulatory effect. VCN did not increase stimulation in mixed lymphocyte cultures between HL-A identical siblings suggesting that the primary effect is to increase the immunogenicity of HL-A antigens present, probably by facilitating cell-to-cell contact. A low, but statistically significant stimulation occurred in some autologous combinations suggesting that a secondary effect of VCN is to alter, or `unmask', antigenic determinants or mitogenic factors on the stimulatory cells.