The B-Cell-Specific src-Family Kinase Blk Is Dispensable for B-Cell Development and Activation

Abstract

The B-cell lymphocyte kinase (Blk) is a src-family protein tyrosine kinase specifically expressed in B-lineage cells of mice. The early onset of Blk expression during B-cell development in the bone marrow and the high expression levels of Blk in mature B cells suggest a possible important role of Blk in B-cell physiology. To study the in vivo function of Blk, mice homozygous for the targeted disruption of the blk gene were generated. In homozygous mutant mice, neither blk mRNA nor Blk protein is expressed. Despite the absence of Blk, the development, in vitro activation, and humoral immune responses of B cells to T-cell-dependent and -independent antigens are unaltered. These data are consistent with functional redundancy of Blk in B-cell development and immune responses.

ACKNOWLEDGMENTS

We are grateful to C. A. Lowell (UCSF) for the gift of anti-Syk antibody and to D. Kitamura (Tokyo Science University) for the gift of anti-BASH antibody. We thank S. Irlenbusch and C. Uthoff-Hachenberg for technical assistance.

This work was supported by the Deutsche Forschungsgemeinschaft through SFB 243. I.M. is supported by a Graduiertenkolleg fellowship from the Deutsche Forschungsgemeinschaft. K.S. is supported by an EMBO long-term fellowship. S.D. is supported by the Howard Hughes Medical Institute and the National Cancer Institute.

G. Texido and I.-H. Su contributed equally to this work.