Analysis of NKG2D expression on CD28

Investigators: Peter Lamprecht, M.D. and Wolfgang L. Gross, M.D.

Location: Department of Rheumatology, University Hospital of Schleswig-Holstein, Campus Luebeck and Rheumaklinik Bad Bramstedt Luebeck and Bad Bramstedt, Germany

Timeline: January 1, 2004 – December 31, 2004

Abstract:  Wegener’s Granulomatosis (WG) is a chronic inflammatory disease characterized by granulomatous lesions and an autoimmune vasculitis. Previously we have shown that circulating Th1-type so-called “late” differentiated or “effector memory” cells lacking the co-stimulatory molecule CD28 are expanded. Expansion of CD28 ¯ T-cells starts early during the disease process and correlates with organ involvement. In granulomatous lesions T-cells also generally lack CD28. Moreover, CD28¯ T-cells are the Th1-type cytokine producing T-cell population within these lesions. Data from in vitro studies suggest that CD28¯ T-cells express the co-stimulatory activating receptor NKG2D under inflammatory conditions. NKG2D interacts with the ligands MICA and MICB which are non-classical MHC-class I antigens expressed on antigen-presenting cells upon infection and cellular distress.
 

We hypothesize that in WG CD28¯ T-cells express NKG2D and interact with MICA and MICB expressed on antigen-presenting within granulomatous lesions. Therefore we want to determine the expression of NKG2D on peripheral blood CD28¯ T-cells by flow cytometry (n=25) and on CD28¯ T-cells within granulomatous lesions by immunohistochemistry (n=5). MICA and MICB expression on antigen-presenting cells within granulomatous lesions will be shown by immunohistochemistry (n=5).
Detection of NKG2D+CD28¯ T-cells interacting with MICA+MICB+ cells would shed new light on the nature of T-cell activation in WG and allow future detailed analysis of possible antigens involved in this process. The analysis might reveal new potential targets for a more specific therapy, for instance DAP 10, which is an adaptor protein necessary for NKG2D signaling.
 

What this means for patients
We see an expansion of a population of specialized, proinflammatory immune cells in WG. These specialized, proinflammatory immune cells are coined CD28¯ T-cells, because they lack a molecule, namely CD28, on their cell surface. We want to analyze whether these CD28¯ T-cells express another molecule, NKG2D, on their cell surface. The NKG2D molecule is important for the activation of CD28¯ T-cells and enables them to sense cellular distress and/or infection on surrounding cells. In that case the surrounding cells express the NKG2D ligands (counterparts) MICA and MICB on their cell surface to communicate with the CD28¯ T-cells. We want to analyze whether peripheral blood CD28¯ T-cells and CD28¯ T-cells within inflammatory lesions in nasal tissue express the NKG2D molecule on their surface and whether their ligands MICA and MICB are expressed on the cell surface of surrounding cells.
 

The proposed analysis will shed new light on the nature of the activation of proinflammatory immune cells in WG and might also reveal new potential targets for a more specific therapy.