The natural TCR locus of this TCR transgenic mouse is still intact and is capable of rearranging. Is there any data out there regarding the frequency at which other productive TCRs are co-expressed with the transgenic receptors on OT-I T-cell surfaces?
Dear Dr Sharma, unlikely you will see satisfactory answer. There is restricted number of mAbs capable to distinguish different Valpha and Vbeta. Obviously, we can say that transgenic TCR is expressed, but we can not see, whether second TCR is expressed too and how much percent of T cells expresses dual (or triple) TCR. General rule is that transgenic TCR expression accelerates passing of T cells via DP stage presuming that endogenous segments may be not rearranged. Second rule is that transgenic beta chain induces allelic exclusion and suppresses rearrangement of endogenous beta chains (in TCR beta chain transgenic mice 80-90% of peripheral T cells carry transgenic beta chain and only 10-20% expresses endogenous ones). Third rule is that allelic exclusion for alpha chains is not so strong and in normal mice T cells with dual TCRs represent significant percent (10-20%) of peripheral repertoire. Theoretically, in TCR transgenic mice three alpha chains may be combined with one (transgenic or endogenous) beta chain. Due to competition (or another unknown mechanisms) simultaneous appearance of two TCRs on the surface of one T cell is rare. The situation is additionally complicated by timing of expression of both alpha and beta chains, and possibility for transgenic T cells come into intraepithelial pool.
It is hard to give exact number. The skewing toward CD8 in total T cells in OT1 mice is very good. This suggests that CD8+ OT1 cells are primarily selected. I would say, there will not be a lot of T cells with second TCR. If second TCR is a problem for you, you need to cross OT1 mice onto Rag knockout background.
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