Signaling capacity of FcgammaRII isoforms in B-CLL cells.
Two main isoforms of Fcgamma receptor II (CD 32) have been described in humans: activatory FcgammaRIIA and inhibitory FcgammaRIIB. We have previously reported that B cells from a subset of chronic lymphocytic leukemia (B-CLL) patients express not only FcgammaRIIB, as normal B lymphocytes, but also the myeloid FcgammaRIIA. The aim of this study was to evaluate the signaling capacity of both FcgammaRII isoforms in B-CLL cells. We found that FcgammaRIIA expressed by leukemic cells failed to induce Ca(2+) mobilization or protein tyrosine phosphorylation, suggesting that the receptor is not functional. By contrast, FcgammaRIIB effectively diminished BCR-triggered ERK 1 phosphorylation, which indicates that it is able to transduce inhibitory signals in B-CLL cells. Moreover, we found that FcgammaRIIB homoaggregation in either B-CLL or non-malignant tonsillar B cells did not result in apoptosis as was reported for murine B splenocytes. Together, these results show that FcgammaRIIB, but not FcgammaRIIA is biologically active in B-CLL cells and might influence leukemic cell physiology in vivo.
Gamberale
Romina
R
Laboratorio de Inmunología, Instituto de Investigaciones Hematológicas, Academia Nacional de Medicina, Pacheco de Melo 3081, 1425 Buenos Aires, Argentina. rgamberale@hematologia.anm.edu.ar
Fernández-Calotti
Paula
P
Sanjurjo
Julieta
J
Arrossagaray
Guillermo
G
Avalos
Julio Sánchez
JS
Geffner
Jorge
J
Giordano
Mirta
M
D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000276:immunology*; D017209:Apoptosis / Q000276:immunology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000276:immunology; D005260:Female; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D020033:Protein Isoforms / Q000276:immunology; D017452:Receptors, IgG / Q000276:immunology*
D015703:Antigens, CD; C080568:Fc gamma receptor IIA; C080571:Fc gamma receptor IIB; D020033:Protein Isoforms; D017452:Receptors, IgG