Armenian Hamster Anti-Mouse CD48 Monoclonal antibody, clone HM48-1 Functional Grade

Mast cells are best known as central effector cells in IgE-mediated type I allergic diseases including asthma and hay fever. An increasing amount of evidence, however, has demonstrated that mast cells are sentinel cells playing a critical role in host defense against invading microbes. Mast cells are located immediately beneath the epithelial surfaces exposed to the outer environment, such as genitourinary and gastrointestinal tracts, skin, and airways. This review discusses recent studies on the critical roles of mast cells in host defense against Gram-negative bacterial infection. Mast cells are equipped with multiple receptors detecting the invading Gram-negative bacteria in both direct (opsonin-independent) and indirect (opsonin-dependent) mechanisms. The former includes Toll-like receptors (TLRs), CD48, and nucleotide-binding oligomerization (NOD) proteins, while the latter includes Fc gamma receptors (Fc gamma Rs) and complement receptors. In addition to the detecting systems, mast cells are also armed with versatile tools to combat and kill Gram-negative bacteria. In response to the recognition of the Gram-negative bacterial infection, mast cells secrete various types of mediators which either regulate host immune system or directly attack the bacteria. Mast cells can also phagocytize and subsequently display the bacterial antigens on their cell surfaces. Moreover, recent findings have revealed the formation of extra-cellular traps by mast cells. Finally this review will especially focus on recent findings on LPS signaling in mast cells, both the functional outcome and the molecular mechanisms.

Most cell surface molecules are glycoproteins consisting of linear arrays of globular domains containing stretches of amino acid sequence with similarities to regions in other proteins. These conserved regions form the basis for the classification of proteins into superfamilies. Recombinant soluble forms of six leukocyte antigens belonging to the Ly-6 (CD59), scavenger receptor (CD5), and immunoglobulin (CD2, CD48, CD4, and Thy-1) superfamilies were expressed in the same Chinese hamster ovary cell line, thus providing an opportunity to examine the extent to which N-linked oligosaccharide processing might vary in a superfamily-, domain-, or protein-dependent manner in a given cell. While we found no evidence for superfamily-specific modifications of the glycans, marked differences were seen in the types of oligosaccharides attached to individual proteins within a given superfamily, The relative importance of local protein surface properties versus the overall tertiary structure of the molecules in directing this protein-specific variation was examined in the context of molecular models, These were constructed using the 3D structures of the proteins, glycan data from this study, and an oligosaccharide structural database. The results indicated that both the overall organization of the domains and the local protein structure can have a large bearing on site-specific glycan modification of cells in stasis, This level of control ensures that the surface of a single cell will display a diverse repertoire of glycans and precludes the presentation of multiple copies of a single oligosaccharide on the cell surface, The glycans invariably shield large regions of the protein surfaces although, for the glycoproteins examined here, these did not hinder the known active sites of the molecules. The models also indicated that sugars are likely to play a role in the packing of the native cell surface glycoproteins and to limit nonspecific protein-protein interactions. In addition, glycans located close to the cell membrane are likely to affect crucially the orientation of the glycoproteins to which they are attached.