[Functional and structural analysis of the Lyb-2 system].
The Lyb-2 system of the mouse is a B cell-specific cell surface molecule encoded by a gene on chromosome 4. We have previously reported that Lyb-2 is involved in an early phase of B cell differentiation, specifically a process mediated by B cell stimulatory factor-1 (BSF-1) or-interleukin 4. It is thus very important to define the functional role and structural features of Lyb-2 molecule for the understanding of the regulatory mechanisms of B cell activation initiated by BSF-1. In our attempt to resolve these issues, we found that Lyb-2 antibody inhibits activation processes mediated by BSF-1 such as induction of Ia antigen on the B cell surface and of IgG1 production in lipopolysaccharide-activated B cells, suggesting that Lyb-2 molecule participates in a signaling event triggered by the binding of BSF-1 to its receptor. In the structural analysis, we found that in contrast to previous reports, Lyb-2 is not a monomer of 45 kilodaltons (kDa) but is composed of two components with molecular weight of 45 kDa and 105 kDa. Reduced and nonreduced two-dimensional electrophoresis analysis further revealed that Lyb-2 molecules are present on the B cell surface in two forms, a disulfide-bonded heterodimer of 45 kDa and 105 kDa chains and a 45 kDa homatrimer. How the structural uniqueness of Lyb-2 is related to its functional expression remains to be determined.
Ashida
T
T
2nd Dept. of Pathology, Asahikawa Medical College.
Kawabata
I
I
Yakura
H
H
D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis* / Q000235:genetics / Q000502:physiology; D000954:Antigens, Surface / Q000032:analysis* / Q000235:genetics; D001402:B-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D015847:Interleukin-4; D007378:Interleukins / Q000502:physiology; D051379:Mice; D008970:Molecular Weight
D000944:Antigens, Differentiation, B-Lymphocyte; D000954:Antigens, Surface; D007378:Interleukins; D015847:Interleukin-4