B lymphocytes in humans express ZAP-70 when activated in vivo

Giovanna Cutrona, Monica Colombo, Serena Matis, Daniele Reverberi, Mariella Dono, Vicenzo Tarantino, Nicholas Chiorazzi, Manlio Ferrarini

Research output: Contribution to journalArticlepeer-review


ZAP-70 is a protein tyrosine kinase initially found in T and NK cells. Recently, this important signaling element was detected in leukemic B cells from a subgroup of patients with B cell chronic lymphocytic leukemia (B-CLL). In this study, ZAP-70 was detected in normal B cells from human tonsils, but not from peripheral blood. The cDNA sequence of B cell ZAP-70 was the same as that in T cells. Germinal center B cells and plasma cells had a substantial proportion of ZAP-70 + cells, while memory and follicular mantle B cells, which contain low numbers of activated B cells, expressed relatively little ZAP-70. A cell fraction of IgD +, CD38 + B cells, which are comprised of many in vivo activated B cells, exhibited the highest levels of ZAP-70. Density gradient fractionation of tonsil B cells confirmed that ZAP-70 was not expressed by resting B cells, but was expressed by buoyant, in vivo activated B cells. In these B cells, the expression of ZAP-70 correlated with that of CD38 and not with that of CD5, a hallmark of B-CLL cells. B-CLL cells are activated cells and their ZAP-70 expression reflects a normal property of activated B cells populations rather than a neoplastic aberration.

Original languageEnglish
Pages (from-to)558-569
Number of pages12
JournalEuropean Journal of Immunology
Issue number3
Publication statusPublished - Mar 2006


  • Activated B cells
  • B cells subsets
  • B-CLL
  • Human B lymphocytes
  • ZAP-70

ASJC Scopus subject areas

  • Immunology


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