A novel epitope of CD59 expressed by primitive human hematopoietic progenitors

Paul J. Simmons, Andrew C.W. Zannettino, Dee Harrison-Findik, Bernadette Swart, Stephen Tomlinson, Beth Hill, Jeannie A. Javni

Research output: Contribution to journalArticlepeer-review


ObjectiveThe aim of this study was to determine the identity of the cell surface molecule on primitive hematopoietic cells recognized by monoclonal antibody HCC-1.Materials and MethodsScreening of a cDNA expression library prepared from human bone marrow stromal cells with HCC-1 yielded a single cDNA, which when expressed in FDCP-1 cells, resulted in the specific acquisition of HCC-1 binding. The cDNA demonstrated complete identity with CD59, a phosphoinositol glycan-linked membrane protein that protects cells against autologous complement attack. The ubiquitous expression of CD59 is in marked contrast to the restricted reactivity of HCC-1. Studies were performed to examine the basis for the novel specificity of HCC-1 for CD59. The epitope on CD59 identified by HCC-1 was mapped using a series of rat/human CD59 chimeric proteins. Immunoprecipitation analyses were performed to determine whether CD59 associates with other membrane proteins.ResultsMutagenesis of Asn18 did not alter the binding of HCC-1 to CD59, suggesting that N-linked carbohydrates are not responsible for the binding specificity of HCC-1. The epitope for HCC-1 was shown to differ from that identified by previously described CD59 antibodies, encompassing residues A31, L33, R55, and L59. An 80 kDa protein co-immunoprecipitated with CD59 in the HCC-1- cell line HL-60 but not in HCC-1+ K562 cells.ConclusionCollectively, these data support the hypothesis that the unique specificity of HCC-1 for CD59 is due in part to recognition of a novel epitope, which is masked as a result of association with an as yet unidentified 80 kDa protein.

Original languageEnglish (US)
Pages (from-to)1474-1483
Number of pages10
JournalExperimental Hematology
Issue number12
StatePublished - 2001

ASJC Scopus subject areas

  • Molecular Biology
  • Hematology
  • Genetics
  • Cell Biology
  • Cancer Research

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