MHC class I and class II determinants and some adhesion molecules are engaged in the regulation of nitric oxide production in vitro by human monocytes stimulated with colon carcinoma cells.

Surface molecules that are involved in tumor-monocyte interactions were studied. The in vitro system in which human blood monocytes are stimulated with human colon carcinoma cells for nitric oxide (NO) production was used. Monoclonal antibodies (mAbs) against various adhesion molecules (LFA-1, ICAM-1, VNR) were unable to block NO production in coculture of monocytes with carcinoma cells. However, anti-CD44, -LFA-3, and -VLA beta 1 chain mAbs effectively blocked NO production. Also mAbs against MHC class I and HLA-DR molecules inhibited, in a dose-dependent manner, No release. It was concluded that some adhesion molecules and MHC class I and/or class II determinants of monocytes may be involved in tumor-monocyte interactions leading to signal transduction for NO production.