T-lymphocyte apoptosis is increased by non-interleukin-2-dependent induction in human mixed lymphocyte cultures.
BACKGROUND
Transplant tolerance is dependent on the apoptotic deletion of allospecific T lymphocytes following interleukin-2 (IL-2)-dependent T-lymphocyte activation. Current immunosuppressive strategies block IL-2 and may prevent T-cell activation. We examined apoptotic alterations in mixed lymphocyte culture (MLC), a model of allospecific lymphocyte activation, by polyclonal rabbit antithymocyte antibody thymoglobulin (rATG) and monoclonal anti-IL-2 receptor antibody basiliximab.


METHODS
Human lymphocytes were isolated using Ficoll-Paque gradient. Cesium-irradiated (2500 rad) stimulator cells (10(6) cells/mL) were cocultured with equal numbers of responder cells. Apoptosis was measured using annexin-V staining and propidium iodide exclusion using flow cytometry. Isolated protein was analyzed using Western blotting with densitometry.


RESULTS
Apoptosis increased at days 3 and 7 in rATG MLC compared with control and basiliximab MLC. Fas was up-regulated in rATG MLC in a dose-dependent manner, whereas basiliximab did not alter fas. FasL was increased initially and at late time points in rATG MLC.


CONCLUSIONS
Polyclonal rATG increased apoptosis and production of the proapoptotic proteins fas and fasL. In contrast, monoclonal basiliximab did not change lymphocyte apoptosis or apoptotic protein production. These results suggest that a specific IL-2 pathway blockade may prevent allospecific tolerance and that a non-IL-2 pathway blockade may encourage apoptosis of allospecifically activated T cells.
Woodside
K J
KJ
Department of Surgery, University of Texas Medical Branch, Galveston, Texas 77555-0534, USA. woodside@umich.edu
Hu
M
M
Gugliuzza
K K
KK
Hunter
G C
GC
Daller
J A
JA
D000961:Antilymphocyte Serum / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology*; D007959:Lymphocyte Culture Test, Mixed; D013601:T-Lymphocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D023001:Transplantation Tolerance / Q000276:immunology
D000961:Antilymphocyte Serum; D007376:Interleukin-2