Different stimulating capacity of B and T lymphocytes in primary and secondary allogeneic reactions: cellular detection of HLA-D products on T lymphocytes.

The present study was undertaken to define the best way to produce and to test primed lymphocyte typing (PLT) cells using B- and T-enriched lymphocyte suspensions. Intrafamilial PLT cells were produced with primed unseparated and T purified lymphocytes against haplo-identical donors' T and B cells. These PLT cells were then restimulated with a panel of related or unrelated individuals' T and B cells and with allogeneic in vitro activated T cells. The best discrimination was obtained when PLT reagents, regardless of the production method, were restimulated by a B-enriched population of peripheral lymphocytes. Furthermore, the results have shown that enriched primed or unprimed T cell suspensions stimulated by enriched T lymphocytes did not give any proliferation. Experiments performed to explain the results led us to distinguish 2 different phenomena: in primary cultures, the addition of monocytes autologous to the responder cell restored the proliferation of enriched T cells stimulated by T lymphocytes. In secondary cultures, the addition of monocytes autologous to the PLT cell did not restore the proliferation of PLT lymphocytes stimulated by enriched T cells. This was shown to be due to the lack of Dr antigen on the stimulating cell: if allogeneically activated T cells were used as stimulating lymphocytes, a DR-specific proliferative response appeared. This correlates with serologic findings were DR determinants are found on activated T cells and not on unprimed T lymphocytes. However, this difference might be only quantitative, since peripheral lymphocytes could be primed by T cells and be DR specifically restimulated.