MUTATION OF UNIQUE REGION OF BRUTONS TYROSINE KINASE IN IMMUNODEFICIENT XID MICE

The cytoplasmic tyrosine kinase, Bruton's tyrosine kinase (Btk, former ly bpk or atk), is crucial for B cell development. Loss of kinase acti vity results in the human immunodeficiency, X-linked agammaglobulinemi a, characterized by a failure to produce B cells. In the murine X-link ed immunodeficiency (XID), B cells are present but respond abnormally to activating signals. The Btk gene, btk, was mapped to the xid region of the mouse X chromosome by interspecific backcross analysis. A sing le conserved residue within the amino terminal unique region of Btk wa s mutated in XID mice. This change in xid probably interferes with nor mal B cell signaling mediated by Btk protein interactions.