Subcellular Localization of the Small GTPase Rab5a in Resting and Stimulated Human Neutrophils

The evidence that small GTPases of the Rab family are regulators of vesicle traffic which can influence various cell functions prompted us to investigate the potential role of one of these proteins, Rab5a, in human neutrophils. In this paper we show that a large amount of Rab5a is present in the cytosol of peripheral blood mature neutrophils. The remaining protein was found to be membrane and azurophilic granule associated. Upon neutrophil challenge with PMA for 10 min the amount of membrane-associated Rab5a was upregulated while the cytosolic content of the protein concomitantly decreased. These findings support the hypothesis that Rab5a could be involved in the mechanism of neutrophil activation by modulating the rate of endocytosis and/or vesicle fusion.     

Large scale purification and immunological characterization of human placental nerve growth factor

Nerve growth factor (NGF) is a protein which plays a critical role in the development and survival of not only peripheral neurons, but possibly also cholinergic brain neurons. The present study describes a procedure for large scale isolation of human NGF of placental origin, and its immunological characterization. A protein species of approximately 26 kDa was obtained, which crossreared characterization. A protein species of approximately 26 kDa was obtained, which crossreacted with antibodies to mouse NGF. Polyclonal and monoclonal anti-mouse NGF antibodies appeared to recognize different bands within this human NGF preparation. Although these polyclonal antibodies recognized both the dimeric and monomeric forms of mouse NGF, the monoclonal antibody recognized only a band corresponding to the dimeric form of mouse NGF.     

Ultrastructural evidence for human mast cell-eosinophil interactions in vitro

We have hypothesized that mast cells (MC) and eosinophils (Eos), the main effectors of allergy, can form an effector unit. These cells co-exist in the inflamed tissues during the late and chronic stages of allergy and have been shown to be capable of influencing each other's survival and activity via soluble mediators. We have recently described couples of receptor-ligands that are expressed on either/both of these cells and that imply a physical interaction. In this study, we have investigated the existence of short-term (60 min) in vitro interactions between human peripheral blood Eos and cord-blood-derived MC by transmission electron microscopy. We have found that MC and Eos adhere to each other; the lipid body content and the granule morphology of co-cultured MC and Eos, respectively, are altered, and the level of Eos peroxidase (EPO) released by co-cultured Eos is elevated. Moreover, the transfer of EPO from Eos to MC and tryptase from MC to Eos has been observed. Our results thus indicate that, when co-cultured, MC and Eos show signs of physical contact and of reciprocal activation. This is the first in vitro evidence of functional physical interactions between human MC and Eos, interactions that might also occur in vivo during allergic diseases.