R. Keller

Mononuclear phagocytes from human bone marrow progenitor cells; morphology, surface phenotype, and functional properties of resting and activated cells

After 3–4 weeks culture of human bone marrow cells in medium supplemented with IL‐3, macrophagc‐ (M‐CSF), and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), the firmly adherent cells exhibited the morphologic features of mononuclear phagocytes and were strongly esterase‐positive. Flow cylometric analysis revealed a rather homogeneous cell population with marked autofluorescence; the large majority of the cells expressed CD14. CD1 la,b, and c. Fc receptors for IgG, FcγRI, II, and III, and HLA class II molecules. Interfcron‐gamma (IFN‐γ). bacteria, and bacterial products modulated expression of some of the surface markers, induced and/ or enhanced respiratory burst, phagoeytic activity, secretion of tumour necrosis factor, and lumouricidal activity; in contrast, these cells were not able to generate reactive nitrogen intermediates.

Suppression of growth of p-815 mastocytoma cells in vitro by drugs increasing cellular cyclic 3',5'-adenosine monophosphate.

Abstract The combined presence of dibutyryl cyclic 3′, 5′- adenosine monophosphate or adenyl cyclase activators and theophylline (which inhibits the breakdown of cyclic AMP) effectively suppressed the growth of a suspension culture of P-185 mastocytoma cells in vitro . As soon as the drugs were withdrawn from the culture, the growth of the tumour cells was fully restored. The observations are taken as support of the concept that cyclic AMP plays an important role in the control of cellular growth. The differences between the present findings and previous reports showing that these drugs had the reverse effect on certain normal cells may reflect differences between normal cells and tumour cells.

Competition between foetal tissue and macrophage-dependent natural tumour resistance.

Prolonged interaction in vitro between C. parvum-induced adherent predominantly phagocytic rat peritoneal cells and syngeneic or xenogeneic tumour targets consistently produces marked cytotoxicity. In the presence of irradiated foetal liver cells, expression of cytotoxicity is blocked in a dose-dependent manner. The ability of liver cells to compete with tumour targets is rapidly lost after birth. Irradiated liver cells from adult donors showed no such competition with tumour cells. The in vivo growth in ascites form of rat fibrosarcoma cells of low immunogenicity is significantly enhanced by irradiated foetal liver cells administered locally shortly before or on the day of tumour-cell challenge. The findings may provide an indication as to the nature of the structures recognized as non-self by mononuclear phagocytes.