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Certain proteins are known to play an important part in the proliferation, differentiation and functional activation of haematopoietic progenitor cells in vitro1,2. These proteins include erythropoietin and various colony-stimulating factors (CSFs), one of which is granulocyte–macrophage colony-stimulating factor (GM-CSF). Recently, both murine3,4and human GM-CSF5–7have been purified to homogeneity and complementary DNAs encoding them have been cloned. Although the in vitro activity of recombinant human GM-CSF has been investigated intensively (refs 5–15; see ref. 8 for a review), little is known about the functional activity of this protein in vivo. There is strong evidence that colony-stimulating activities produced by various human and murine tumour tissues and cell lines can stimulate granulopoiesis in mice16–26, as can human urinary extracts27,28. A partially purified preparation of human urinary colony-stimulating factor, however, proved only marginally effective in stimulating granulopoiesis in humans29. All these studies suffer from the lack of a homogeneous preparation of colony-stimulating factor. It has recently been shown that recombinant murine multi-CSF or interleukin-3 can stimulate haematopoiesis in mice in vivo30,31. Large-scale production of recombinant human GM-CSF now permits us to examine its effects in vivo using a primate model. We find that the continuous infusion of GM-CSF in healthy monkeys rapidly elicits a dramatic leukocytosis and a substantial reticulocytosis. A similar effect has been observed in one pancytopenic, immunodeficient rhesus macaque. These results suggest that GM-CSF could prove useful in several clinical situations.

LITERATURE on villus pattern in the rhesus monkey is scarce. Lineback1noted, using ordinary histological methods, that villi were flange-shaped in the duodenum and that towards the lower end of the ileum they attained a more typical finger-like form. It is, however, difficult to decide firmly about the shape of villi without dissection microscopy. Booth et al.2pointed out that leaf-like villi may appear finger-like in a histological section depending on its plane. This communication reports on the configuration of intestinal villi in apparently normal rhesus monkeys utilizing the technique of dissection microscopy.