Inhibition of graft-versus-host disease by interleukin-2 treatment is associated with altered cytokine production by expanded graft-versus-host-reactive CD4+ helper cells.
In a fully MHC plus multiple minor antigen-mismatched murine bone marrow transplantation (BMT) model, we have demonstrated that a short course of high dose IL-2, begun on the day of BMT, protects against graft-versus-host disease (GVHD). This inhibitory effect is directed against donor CD4+ cells. To determine whether the mechanism of IL-2-induced GVHD protection involves clonal deletion or anergy of host-reactive donor T helper cells (Th), we performed limiting dilution analyses to measure the frequency of activated Th that reacted to donor, host, and third-party antigens in GVHD control and IL-2-protected mice. Marked and specific expansion of host-reactive Th was observed to a similar extent in GVHD control and IL-2-protected mice by day 5 after BMT, and the number of these cells in the spleen increased by several orders of magnitude between days 3 and 5 after BMT, which suggests that recirculation from other tissues occurred in this period. A high proportion (approximately 80%) of donor T cells expressed CD25 in both GVHD control and IL-2-protected mice on day 4 after BMT, which suggests a high level of bystander T cell activation. Since marked quantitative differences in the GVH response were not observed between GVHD control and IL-2-protected mice, we assessed both groups for qualitative differences in the Th response. Spleen cells isolated in the first 8 days after BMT were cultured with host-type, donor-type, or third-party stimulators or without stimulators, and cytokines were measured in supernatants harvested at 24 hr. GVHD was associated with marked increases in supernatant IFN-gamma levels from day 3 to day 6 after BMT, and with increases in IL-2 levels compared with naive A/J controls or syngeneic BMT controls stimulated with host antigens. Production of these cytokines was specifically induced by host-type antigens. Supernatants from spleens of IL-2-treated mice showed delayed kinetics of IFN-gamma production, and tended to contain higher levels of IL-4 in response to host antigen compared with GVHD controls on days 2 and 4 after BMT. Both IL-4 and IFN-gamma were produced almost exclusively by CD4+ cells in spleens of GVHD control and IL-2-protected mice on day 4. However, no consistent difference was observed between the groups in supernatant IL-2 or IL-10 levels, ruling out a simple Th1 to Th2 switch.(ABSTRACT TRUNCATED AT 400 WORDS)
Wang
M G
MG
Transplantation Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Boston 02129, USA.
Szebeni
J
J
Pearson
D A
DA
Szot
G L
GL
Sykes
M
M
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism; D016207:Cytokines / Q000096:biosynthesis*; D005260:Female; D006086:Graft vs Host Disease / Q000517:prevention & control*; D006087:Graft vs Host Reaction; D007371:Interferon-gamma / Q000096:biosynthesis; D016753:Interleukin-10 / Q000096:biosynthesis; D007376:Interleukin-2 / Q000096:biosynthesis / Q000627:therapeutic use*; D015847:Interleukin-4 / Q000096:biosynthesis; D051379:Mice; D008810:Mice, Inbred C57BL; D015375:Receptors, Interleukin-2 / Q000032:analysis; D006377:T-Lymphocytes, Helper-Inducer / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D016207:Cytokines; D007376:Interleukin-2; D015375:Receptors, Interleukin-2; D016753:Interleukin-10; D015847:Interleukin-4; D007371:Interferon-gamma