Submitted January 7, 2009
Accepted April 22, 2009
Increased frequency (12%) of circulating CLL-like B-cell clones in healthy individuals using a high-sensitive multicolor flow cytometry approach
Wendy G. Nieto, Julia Almeida, Alfonso Romero, Cristina Teodosio, Antonio Lopez, Ana F. Henriques, Maria Luz Sanchez, Maria Jara-Acevedo, Ana Rasillo, Marcos Gonzalez, Paulino Fernandez-Navarro, Tomas Vega, and Alberto Orfao*
Instituto de Biologia Molecular y Celular del Cancer, Centro de Investigacion del Cancer, IBMCC (CSIC-USAL) & Cytometry Service and Department of Medicine, University of Salamanca, Salamanca, Spain
Gerencia de Atencion Primaria de Salud de Salamanca, Sanidad de Castilla y Leon (SACYL), Castilla y Leon, Spain
Servicio de Hematologia, Hospital Universitario de Salamanca, Salamanca, Spain
Centro de Atencion Primaria de Salud de Ledesma Salamanca, Sanidad de Castilla y Leon (SACYL), Castilla y Leon, Spain
Direccion General de Salud Publica y Consumo, Junta de Castilla y Leon, Castilla y Leon, Spain
* Corresponding author; email: orfao{at}usal.es.
Monoclonal B-cell lymphocytosis (MBL) indicates the presence of circulating monoclonal B cells below 5x109/L in otherwise healthy individuals. Recently, it has been reported that circulating CLL-like B cells can be detected using 4- or 5-multicolor flow cytometry in 5%-7% of adults with normal lymphocyte counts. We investigated the frequency of circulating monoclonal B cells in 608 healthy individuals >40 years with normal blood counts, using a high-sensitive 8-color flow cytometry approach and systematic screening for > 5x106 total PB leucocytes. We show that the frequency of PB monoclonal B cells is markedly higher than previously reported (12% for CLL-like B cells, found at frequencies of 0.17±0.13x109 cells/L), the incidence progressively increasing with age. Most cases (62%) showed clonal B-cell levels below the maximum sensitivity of the techniques described by others (<0.01%), supporting the notion that detection of MBL may largely depend on the sensitivity of the flow-cytometry approach used.
