A rat monoclonal anti-(human CD2) and L-leucine methyl ester impacts on human/SCID mouse graft and B lymphoproliferative syndrome.

The transfer of human peripheral blood mononuclear cells (hu-PBMC) from adult Epstein-Barr-virus(EBV)-seropositive donors in SCID (severe combined immunodeficiency) mice frequently leads to the development of a human B lymphoproliferative syndrome (hu-BLPS). Therefore, as 90% of adult potential donors are EBV-seropositive, efforts have to be made to avoid the occurrence of this B lymphoproliferative disorder. McCune et al. [Science 241:1632 (1988)] used human fetal organs for a human SCID graft. This system does not give rise to hu-BLPS but human fetal organs are much less available than peripheral blood leucocytes. The experiments reported in this paper show how crucial is the presence of functional T lymphocytes for a graft to take and for development of hu-BLPS in hu-PBMC-reconstituted SCID mice, since inhibition of T lymphocyte by a rat anti-(human CD2) monoclonal antibody (LO-CD2a) during the first 10 days of the graft prevents successful engraftment of human normal lymphocytes as well as hu-BLPS in SCID mice. The transfer of B cells alone or B cells plus monocytes in SCID mice does not permit either long-term engraftment or development of hu-BLPS. We also demonstrate that hu-PBMC treated with L-leucine methyl ester are less susceptible to the development of hu-BLPS after engraftment in SCID mice than are untreated hu-PBMC. The mechanism of action of L-leucine methyl ester on these cells is discussed.