Analysis of CD97 Expression and Manipulation: Antibody Treatment but Not Gene Targeting Curtails Granulocyte Migration

Abstract

The heptahelical receptor CD97 is a defining member of the EGF-TM7 family of adhesion class receptors. In both humans and mice, CD97 isoforms are expressed with variable numbers of tandemly arranged N-terminal epidermal growth factor-like domains that facilitate interactions with distinct cellular ligands. Results from treatment of mice with mAbs in various disease models have suggested a role for CD97 in leukocyte trafficking. Here, we aimed to thoroughly characterize the expression profile of CD97, and delineate its biological function. To this end, we applied a novel polyclonal Ab, which is the first antiserum suitable for immunohistochemistry, and combined this analysis with the study of Cd97-lacZ knock-in mice. We show that similar to the situation in humans, hematopoietic, epithelial, endothelial, muscle, and fat cells expressed CD97. Despite this broad expression pattern, the Cd97−/− mouse that we created had no overt phenotype, except for a mild granulocytosis. Furthermore, granulocyte accumulation at sites of inflammation was normal in the absence of CD97. Interestingly, application of CD97 mAbs blocked granulocyte trafficking after thioglycollate-induced peritonitis in wild-type but not in knock-out mice. Hence, we conclude that CD97 mAbs actively induce an inhibitory effect that disturbs normal granulocyte trafficking, which is not perturbed by the absence of the molecule.

Therapeutic Antibody Targeting of CD97 in Experimental Arthritis: the Role of Antigen Expression, Shedding, and Internalization on the Pharmacokinetics of Anti-CD97 Monoclonal Antibody 1B2

“…Accumulation of 1B2, and not of the isotype control 3D7, was predominantly found in spleen and lung tissue (Fig. 3C), which is in accordance with reported mCD97 expression in spleen and lung (15). Of note, the spleen and lung tissues of animals receiving 1B2 (or 3D7) treatment, when subjected to histopathological examination, did not reveal any changes (data not shown).…”

“…Evidence for the relevance of such an interaction in humans was found by the colocalization of CD55 ϩ synoviocytes and CD97 ϩ macrophages in synovial tissue (17). A second putative mechanism of 1B2 efficacy in vivo was hypothesized recently based on evidence suggesting that 1B2 activates CD97, rather than blocking its interaction with CD55 (15). In this respect, it is highly interesting that in vitro internalization of 1B2 after binding to cellular CD97 was observed.…”

“…CD97 is expressed by cells of the immune system, with highest expression levels in myeloid cells and in nonhematopoietic tissues, including lung and smooth muscle (14,15). CD97 is thought to have a role in inflammatory cell recruitment.…”

“…Both the 1B2 and 1C5 mAbs, recognizing different EGF domains of mCD97 (Fig. 1A), have shown an in vivo effect on cell recruitment in murine inflammation models (13,15,16). Interestingly, increased levels of soluble CD97 (sCD97) have been found in synovial fluids of patients with rheumatoid arthritis (RA) (5,17).…”

Cell Adhesion Receptor GPR133 Couples to Gs Protein

“…Adhesion GPCR are characterized by long extracellular N termini, which are composed of multiple functional domains, a seven-transmembrane spanning (7TM) domain, and a cytoplasmic tail. Adhesion GPCR are believed to play a role in immune functions (3,4), angiogenesis (5), cell polarity (6,7), and development (8,9). Mutations in some members of the protein family were identified as the cause of inherited developmental defects in humans such as Usher syndrome (VLGR1) (10) and bilateral frontoparietal polymicrogyria (GPR56) (11).…”