First article which touches antigen transfer was published in 2004. Experiments from this study reveal that clonal deletion of autoreactive CD4 T cells, apart from CD8 T cells, requires indirect presentation of TRAs by bone marrow (BM) derived APCs. Direct presentation of TRAs by mTECs was shown to be insufficient in this case. Requirement of indirect presentation of some mTEC-derived TRAs in the case of recessive tolerance was perceived also by additional studies which both firstly demonstrated antigen transfer as an instrument that enables this process.  Need of TRA indirect presentation is probably closely related with above mentioned "processing of TRAs by different microenvironments".
N.B.: BM derived APCs don´t express TRAs, this process is uniquely dedicated to mTECs. Exception is represented by thymic B cells which were shown to express TRAs and Aire.