The physiological mechanism of clearance of the mononuclear phagocyte growth factor, colony-stimulating factor 1 (CSF-1), from the circulation of normal mice was investigated by following the fate of a trace amount of i.v.injected '25I-labeled CSF-1. Macrophages selectively cleared CSF-1 by CSF-1 receptor-mediated endocytosis and degraded the growth factor intracellularly. This manner of clearance provides a feedback control mechanism whereby the rate of macrophage production is determined by the number of mature macrophages.

Background We evaluated the importance of measuring early vaginal levels of eight BV-associated bacteria, at two points in pregnancy, and the risk of spontaneous preterm delivery (SPTD) among pregnant women and the subgroup of pregnant women with a history of preterm delivery (PTD). Methods This prospective cohort study enrolled women at five urban obstetric practices at Temple University Hospital in Philadelphia PA. Women with singleton pregnancies less than 16 weeks gestation self-collected vaginal swabs at two points in pregnancy, prior to 16 weeks gestation and between 20-24 weeks gestation, to measure the presence and level of eight BV-associated bacteria. Women were followed-up for gestational age at delivery via medical records. Results Among women reporting a prior PTD, women with higher levels of Leptotrichia/Sneathia species, BVAB1 and Mobiluncus spp., prior to 16 weeks gestation, were significantly more likely to experience a SPTD. In addition, pregnant women with a prior PTD and increasing levels of Leptotrichia/Sneathia species (aOR: 9.1, 95% CI: 1.9-42.9), BVAB1 (aOR: 16.4, 95% CI: 4.3-62.7) or Megasphaera phylotype 1 (aOR: 6.2, 95% CI: 1.9-20.6), through 24 weeks gestation, were significantly more likely to experience a SPTD. Among the overall group of pregnant women, the levels of BV-associated bacteria were not related to SPTD. Conclusion Among the group of women reporting a prior PTD, increasing levels of BVAB1, Leptotrichia/Sneathia species, and Megasphaera phylotype 1, through mid-pregnancy were related to an increased risk of SPTD.

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