title: Another Piece of the Puzzle of Podocyte B7-1 Expression: Lupus Nephritis.
abstract: OBJECTIVE
  Lupus nephritis (LN) is a frequent complication and a major predictor of poor prognosis of systemic lupus erythematosus. Immune complex deposition and T cell infiltration are crucial events in LN pathogenesis. B7-1 (CD80), normally expressed by antigen-presenting cells, is one of the major co-stimulators of T-cell activation through the binding with its counter-receptors CD28 and cytotoxic T-lymphocyte antigen-4. Unexpectedly, B7-1 induction was described at the podocyte level in patients affected by different renal diseases, including LN. These observations suggested a novel exciting function for B7-1 as a biomarker of podocyte injury, and hence that B7-1 inhibitory drugs could serve as podocyte-targeted treatment of intractable renal diseases. However, subsequent studies hardly questioned the reliability of B7-1 detection assays and the therapeutic efficacy of B7-1 blockade in proteinuric patients, casting doubts on B7-1 expression by podocytes. Here, we thoroughly investigated whether B7-1 was indeed expressed by podocytes in LN, before even considering employing B7-1 blockade in patients with severe manifestations of LN and unfavourable prognosis.
  
  
  METHODS
  Applying different immunohistochemical assays with 4 primary antibodies, we analysed kidney biopsies from 42 LN patients at different stages of the disease, and from NZB/NZW mice, an LN model.
  
  
  RESULTS
  B7-1 was not induced in podocytes in human and murine LN; instead its expression was confined to infiltrating inflammatory cells.
  
  
  CONCLUSIONS
  B7-1 is not expressed by podocytes in LN. A renoprotective effect of B7-1 blockade in LN patients cannot be ruled out but, if confirmed, cannot be the result of an effect on podocyte B7-1.
authors.affiliation: IRCCS - Istituto di Ricerche Farmacologiche Mario Negri, Centro Anna Maria Astori, Science and Technology Park Kilometro Rosso, Bergamo, Italy.
authors.forename: Rubina
authors.initials: R
authors.lastname: Novelli
authors.forename: Elena
authors.initials: E
authors.lastname: Gagliardini
authors.forename: Barbara
authors.initials: B
authors.lastname: Ruggiero
authors.forename: Ariela
authors.initials: A
authors.lastname: Benigni
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Remuzzi
mesh_terms: D000818:Animals; D018122:B7-1 Antigen / Q000276:immunology*; D005260:Female; D006801:Humans; D008181:Lupus Nephritis / Q000276:immunology*; D008297:Male; D051379:Mice; D050199:Podocytes / Q000276:immunology*
chemical_list: D018122:B7-1 Antigen