Proliferation of a subpopulation of human peripheral blood monocytes in the presence of colony stimulating factors may contribute to the inflammatoryprocess in diseases such as rheumatoid arthritis

Apart from acting on hemopoietic progenitor cells, colony stimulating facto rs (CSFs) have been shown to be involved in the activation, survival, proli feration and differentiation of more mature cells of the monocyte/macrophag e lineage. There is evidence that a proportion of human peripheral blood mo nocytes can proliferate in response to CSF-1, (also known as M-CSF) and gra nulocyte-macrophage-CSF (GM-CSF). CSFs have been shown to be at elevated le vels in the synovial fluid of RA patients and thus local proliferation of m onocyte/macrophage within an inflamed lesion may contribute re, the local t issue hyperplasia evident in inflammatory conditions. Flow cytometric analy sis of surface antigen expression and cytokine production in response to li popolysaccharide stimulation has been used to characterise the proliferatin g subpopulation of monocytes. Further characterization :de new and importan t infor-and subsequent isolation of this subpopulation of monocytes may pro vide information necessary in understanding inflammatory diseases such as r heumatoid arthritis, where local proliferation at the site of inflammation may be a key factor contributing to the chronicity of the disease.