Induction of mouse monocyte-macrophage replication by a mesangial cell-derived factor

Conditioned media of cultured mouse mesangial cells (possessing microfilaments) were shown to contain a factor that stimulated splenic monocytes-macrophages and blood monocytes to replicate. Replicated cells were shown to express MAC-1 antigen as demonstrated by immunofluorescence with anti-MAC 1 and to possess Fc receptors as evidenced by their capacity to ingest sensitized erythrocytes. Preliminary characterization revealed the following characteristics: by Amicon ultrafiltration, fractions greater than 100,000 daltons were shown to have biologic activity; chromatofocusing of these active fractions revealed a peak of activity associated with fractions having pH 4; heating to 100 degrees C for 10 minutes abolished almost all activity, whereas trypsin treatment was without effect. The observations suggest a mechanism by which mesangial cells may modulate the proliferation of monocytes-macrophages that infiltrate the glomerulus in glomerulonephritis.