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

✍ Scribed by Giovanna Cutrona; Monica Colombo; Serena Matis; Daniele Reverberi; Mariella Dono; Vincenzo Tarantino; Nicholas Chiorazzi; Manlio Ferrarini

• Book ID: 102824514
• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 692 KB
• Volume: 36
• Category: Article
• ISSN: 0014-2980
• DOI: 10.1002/eji.200526355

✦ Synopsis

Abstract

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.