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Mast cells are well known for their harmful role in IgE-mediated hypersensitivity reactions, but their physiological role remains a mystery. Several recent studies have reported that mast cells play a critical role in innate immunity in mice by releasing tumor necrosis factor alpha (TNF-alpha) to recruit neutrophils to sites of enterobacterial infection. In some cases, the mast cell TNF-alpha response was triggered when these cells directly bound FimH on the surface of Escherichia coli. We have identified CD48, a glycosylphosphatidylinositol-anchored molecule, to be the complementary FimH-binding moiety in rodent mast cell membrane fractions. We showed that (i) pretreatment of mast cell membranes with antibodies to CD48 or phospholipase C inhibited binding of FimH+ E. coli, (ii) FimH+ E. coli but not a FimH- derivative bound isolated CD48 in a mannose-inhibitable manner, (iii) binding of FimH+ bacteria to Chinese hamster ovary (CHO) cells was markedly increased when these cells were transfected with CD48 cDNA, and (iv) antibodies to CD48 specifically blocked the mast cell TNF-alpha response to FimH+ E. coli. Thus, CD48 is a functionally relevant microbial receptor on mast cells that plays a role in triggering inflammation.

Type

Journal article

Journal

Proc Natl Acad Sci U S A

Publication Date

06/07/1999

Volume

96

Pages

8110 - 8115

Keywords

Adhesins, Bacterial, Adhesins, Escherichia coli, Animals, Antigens, CD, Bacterial Adhesion, CD48 Antigen, CHO Cells, Cloning, Molecular, Cricetinae, Escherichia coli, Fimbriae Proteins, Glycosylphosphatidylinositols, Male, Mast Cells, Mice, Mice, Inbred BALB C, Recombinant Proteins, Transfection, Tumor Necrosis Factor-alpha, Type C Phospholipases