The diversity of in-frame TCR delta chain transcripts in aging SCID mice

From spleen, liver, bone marrow, and gut of old C.B-17 scid/scid (SCID) mice, TCR delta chain transcripts were amplified by the polymerase chain reaction (PCR) using V delta 1-, V delta 2-, V delta 3-, V delta 4-, V delta 5-, V delta 6-, and C delta-specific primers. Selectively amplified, TCR delta-chain-encoding cDNA from these organs of five old SCID mice was cloned, and 175 randomly selected clones were sequenced. In this panel, 44 distinct rearrangement events were detected, 82% (36/44) of which were in-frame. For V delta 2, V delta 4, V delta 5, and V delta 6, 34 in-frame transcripts were found in five old SCID mice. No potentially functional transcript containing V delta 3 was found and an unusual type of transcript containing the V delta 1 gene segment spliced directly in-frame to C delta was the predominant type of V delta 1 expression. Junctional diversity was evident in most sequenced clones indicating an extensive potential diversity of SCID-derived TCR delta chains. Identical transcripts were amplified from different organs of the same old SCID mouse. No organ-specific expression of V delta genes was evident. TCR delta chain transcripts could be neither amplified from young SCID mice nor from young SCID mice nor from young or old scid/scid nu/nu mice (bred on a BALB/c background). Hence, an apparently thymus-dependent development of oligoclonal populations of TCR delta+ cells is observed in old SCID mice.