title: Targeted deletion of CD44v7 exon leads to decreased endothelial cell injury but not tumor cell killing mediated by interleukin-2-activated cytolytic lymphocytes.
abstract: In the current study, we investigated the nature and role of CD44 variant isoforms involved in endothelial cell (EC) injury and tumor cell cytotoxicity mediated by IL-2-activated killer (LAK) cells. Treatment of CD44 wild-type lymphocytes with IL-2 led to increased gene expression of CD44 v6 and v7 variant isoforms and to significant induction of vascular leak syndrome (VLS). CD44v6-v7 knockout (KO) and CD44v7 KO mice showed markedly reduced levels of IL-2-induced VLS. The decreased VLS in CD44v6-v7 KO and CD44v7 KO mice did not result from differential activation and expansion of CD8+ T cells, NK, and NK-T cells or from altered degree of perivascular lymphocytic infiltration in the lungs. LAK cells from CD44v7 KO mice showed a significant decrease in their ability to adhere to and mediate lysis of EC but not lysis of P815 tumor cells in vitro. CD44v7-mediated lysis of EC by LAK cells was dependent on the activity of phosphatidylinositol 3-kinase and tyrosine kinases. Interestingly, IL-2-activated LAK cells expressing CD44hi but not CD44lo were responsible for EC lysis. Furthermore, lysis of EC targets could be blocked by addition of soluble or enzymatic cleavage of CD44v6-v7-binding glycosaminoglycans. Finally, anti-CD44v7 mAbs caused a significant reduction in the adherence to and killing of EC and led to suppression of IL-2-induced VLS. Together, this study suggests that the expression of CD44v7 on LAK cells plays a specific role in EC injury and that it may be possible to reduce EC injury but not tumor cell killing by specifically targeting CD44v7.
authors.affiliation: Departments of Microbiology and Immunology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: McKallip
authors.forename: Michael
authors.initials: M
authors.lastname: Fisher
authors.forename: Yoonkyung
authors.initials: Y
authors.lastname: Do
authors.forename: Andras K
authors.initials: AK
authors.lastname: Szakal
authors.forename: Ursula
authors.initials: U
authors.lastname: Gunthert
authors.forename: Prakash S
authors.initials: PS
authors.lastname: Nagarkatti
authors.forename: Mitzi
authors.initials: M
authors.lastname: Nagarkatti
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D042783:Endothelial Cells / Q000473:pathology; D004730:Endothelium, Vascular / Q000473:pathology; D004789:Enzyme Activation; D005091:Exons; D005260:Female; D005434:Flow Cytometry; D006023:Glycoproteins / Q000096:biosynthesis; D018960:Hyaluronan Receptors / Q000096:biosynthesis / Q000235:genetics*; D007376:Interleukin-2 / Q000378:metabolism; D015979:Killer Cells, Lymphokine-Activated / Q000378:metabolism*; D008024:Ligands; D008168:Lung / Q000276:immunology; D008214:Lymphocytes / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008934:Mitogens / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000473:pathology; D015854:Up-Regulation
chemical_list: C112697:CD44v6 antigen; C476399:Cd44 protein, mouse; D006023:Glycoproteins; D018960:Hyaluronan Receptors; D007376:Interleukin-2; D008024:Ligands; D008934:Mitogens; D020033:Protein Isoforms; D012313:RNA; D019869:Phosphatidylinositol 3-Kinases