Knock-in and conditional knock-out mice for studies on autoimmunity and cancer development

Variable (V) regions of immunoglobulins are highly diversified and contain antigenic determinants (idiotopes, abbreviated Id). A mouse myeloma (MOPC315) secretes an IgA myeloma protein with lambda2 light (L) chains. The particular lambda2 chain, lambda2(3 15), contains an Id-peptide (aa 91-101), that when presented on MHC class II is recognized by CD4+ Id-specific T cells. Based on this system we developed mice transgenic for the lambda 2(315) L chain (Id+ mice) and mice transgenic for a TCR that recognize the particular Id-peptide presented on MHC class II molecules (Id-specific TCR transgenic mice). Thus, we have developed a transgenic mouse model in which mice first develop autoimmunity and later cancer (B lymphomas). The disease development is caused b y B cells receiving chronic stimulation by T cells in a process called Id-driven T-B collaboration. In the experiments on Id-driven T-B collaboration, the specificity of Id+ B cells are restrained only by a fixed L chain that can pair with any of a polycl onal repertoire of H-chains. This polyclonality of H-chains makes study of non-linked Id-driven T-B collaboration cumbersome. The introduction into the system of VH315, and thus monoclonality of the B cell receptor, by use of knock-in technology, will all ow a number of elegant experiments. The present project has two aims. (I) To establish VH knock-in mice which will allow us to study the influence of the B cell receptor on Id-driven T-B collaboration. (II) To establish VH and VL conditional knock-out mi ce to see if turning off BCR expression can abrogate chronic Id-driven T-B collaboration and thus prevent autoimmunity and lymphoma. The experiments of the current project proposal will be carried out in collaboration with a pioneer in the field, Klaus Ra jewsky, Harvard University.