B cell memory in xid mice is long-lived despite reduced memory B cell frequency.

Ridderstad A, Tarlinton DM. B Cell Memory in xid Mice is Long-Lived Despite Reduced Memory B CellFrequency. Scand J Immunol 1997;45:655–659Brutons tyrosine kinase (Btk) deficient xid mice have a diminished primary T cell dependent immuneresponse, resulting in a reduced memory B cell frequency. Boosting at 35 days post primary immunization,however, generates a normal secondary immune response, indicating a functional memory B cell compart-ment. The longevity of B cell memory appears to depend on both the presence of antigen and expression ofcell survival genes such as bcl-2. Since there is a natural decay in the number of memory B cells over time andsince xid B cells have been demonstrated to have reduced Bcl-2 levels, we aimed at determining whether Bcell memory of xid mice would be long-lasting. This report demonstrates that memory B cell precursors aredetectable in xid mice more than 100 days after primary immunization. Furthermore, a secondary immuneresponse of normal magnitude and kinetics can be generated in xid mice at 150 days after primaryimmunization indicating that B cell memory is long-lived inxid mice. Thus, although survival of B cellmemory is presumably dependent on immunoglobulin (Ig)-mediated interaction with antigen, this interactiondoes not depend solely on signalling through Btk.Anna Ridderstad, The Walter and Eliza Hall Institute of Medical Research, PO Royal Melbourne Hospital,Victoria 3050, Australia