R Lobell | PubMed Health

PubMed1997

Increased growth promoting but not mast cell degranulation potential of a covalent dimer of c-Kit ligand.

The native form of soluble c-kit ligand (KL) is a noncovalent dimer. We have isolated a soluble, disulfide-linked dimer of murine KL (KL-CD) by expressing KL in Escherichia coli and refolding the denatured protein under conditions that promote the formation of both noncovalent dimers (KL-NC) and KL-CD. KL-CD exhibits a 10- to 15-fold increase in the ability to stimulate the growth of both the human megakaryocytic cell line MO7e and murine bone marrow-derived mast cells relative to KL-NC. Colony-forming assays of murine bone marrow progenitor cells also reflected this increased potency. However, KL-CD and KL-NC are equally able to prime mast cells for enhanced IgE-dependent degranulation in vitro and activate mast cells in vivo. Improving the growth-promoting activity of KL without changing its mast cell activation potential suggests that KL-CD or a related molecule could be administered in the clinic at doses that stimulate hematopoietic recovery while avoiding significant mast cell activation.

Animals↗

PubMed1997

A soluble chimeric complement inhibitory protein that possesses both decay-accelerating and factor I cofactor activities.

A chimeric gene was constructed from the genes coding for the human complement regulatory proteins, membrane cofactor protein (CD46) and decay-accelerating factor (CD55). The recombinant chimeric gene was transfected into Chinese hamster ovary cells. The gene product is a soluble, glycosylated, 110-kDa protein named complement activation blocker-2 (CAB-2). This protein possesses both factor I cofactor activity and decay-accelerating activity, and inactivates classical and alternative C3/C5 convertases in vitro. The specific activity of CAB-2 against cell-associated convertases is greater than that of soluble forms of either membrane cofactor protein or decay-accelerating factor or of both factors combined. CAB-2 also blocks the activation of complement in vivo, inhibiting both the Arthus reaction and Forssman shock in guinea pigs. Studies in rats demonstrate CAB-2 to exhibit favorable biphasic pharmacokinetics with a t1/2 alpha of 10 min and a t1/2 beta of 8 h; the beta phase accounts for 93% of the administered dose. CAB-2 may be an effective therapeutic treatment of acute human diseases in which excessive complement activation causes damage to normal tissues.

Anaphylaxis↗