RIII S/J (H-2(r)). An inbred mouse strain with a massive deletion of T cell receptor V(β) genes

We have identified an inbred strain of mouse, RIII S/J (H-2(r)), that has the largest known deletion of the TCR V(β) genes by screening with mAb and TCR V(β) specific probes. Upon screening of PBL with mAb F23.1, which is specific for V(β)8 TCR, RIII S/J was found to be negative. On further screening with mAb KJ 23a, which is specific for V(β)17a TCR, RIII S/J was completely negative. We next tested RIII S/J with mAb 44-22-1, which is specific for V(β)6 TCR, and found it also to be negative. The (B10 x RIII)F₁ mice showed a 50% expression of V(β)6 gene, indicating a genomic rather than a clonal deletion. mAb KJ25, detecting V(β)3, was positive in RIII S/J, denoting the downstream boundary for the deletion. Southern blot analysis of liver DNA using TCR V(β)-specific probes confirmed the deletion of V(β)8 gene subfamily, along with V(β)9, V(β)11, V(β)12, and V(β)13 genes similar to the known TCR V(β) deletion mutants (SWR, SJL, C57L, and C57Br). In addition, RIII S/J is missing V(β)6, V(β)15, and V(β)17 genes. Our mapping of the deletion indicates that RIII S/J has lost ~130 kb of V(β) chromosome and with it 13 V(β) genes out of the known 21 V(β) genes of the TCR. The deletion is marked by the presence of V(β)10 gene upstream and V(β)3 gene downstream.