Unmodified pancreatic islet allograft rejection results in the preferential expression of certain T cell activation transcripts.
Polymerase chain reaction-assisted reverse transcription was used to study the temporal course of rejection in unmodified recipients of murine pancreatic islet cell allografts (DBA/2-->B6AF1) by using syngeneic tissues as controls. The histologic appearance of the grafts was analyzed in parallel. Preproinsulin and constant region of the TCR-beta chain transcripts were studied as markers of graft integrity and infiltrating T cell mass, respectively. The participation of certain cytokines and CTL were analyzed by the detection of IL-2, IFN-gamma, IL-4, and CTL-specific serine protease (granzyme B) transcripts. The time-related disappearance of intragraft preproinsulin transcripts correlated with graft destruction, whereas the intensity of intragraft TCR-beta chain transcript levels correlated with the magnitude of mononuclear leukocyte infiltration in allografts. In unmodified allografts, the magnitude of IL-2 and IFN-gamma intragraft mRNA levels correlated with the intense mononuclear leukocyte infiltrate found on histologic examination at day 8. Only after stable IL-2 gene transcription on day 8 does evidence of graft destruction become apparent, indicating that IL-2 gene activation is closely related to and probably required for expression of alloimmune cytopathic processes. In contrast, IL-4 transcripts were absent or detected in low copy number throughout this time course. Intragraft expression of granzyme B mRNA, a CTL-specific transcript, peaked from day 8 to day 12 in allografts compared with syngeneic grafts or normal tissue. In syngeneic grafts IL-2 and/or IL-4 mRNA was essentially not detected. Although IFN-gamma and granzyme B transcripts were detected in syngeneic grafts, after 4 days the levels of detected transcripts were far less than those noted in allografts. In vivo detection of intragraft IL-2 transcripts in the relative absence of detectable IL-4 transcripts strongly suggests IL-2-dependent immune effector mechanisms are associated with, and perhaps responsible, for allograft rejection. Apparently IL-4-dependent effector mechanisms are not necessary for allograft rejection.
O'Connell
P J
PJ
Harvard Medical School, Department of Medicine, Beth Israel Hospital, Boston, MA 02215.
Pacheco-Silva
A
A
Nickerson
P W
PW
Muggia
R A
RA
Bastos
M
M
Kelley
V R
VR
Strom
T B
TB
D000818:Animals; D001483:Base Sequence; D006084:Graft Rejection; D007328:Insulin; D007371:Interferon-gamma / Q000235:genetics*; D007376:Interleukin-2 / Q000235:genetics*; D015847:Interleukin-4 / Q000235:genetics*; D016381:Islets of Langerhans Transplantation; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D008969:Molecular Sequence Data; D011384:Proinsulin / Q000235:genetics; D011498:Protein Precursors / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis*; D013601:T-Lymphocytes / Q000502:physiology*; D014184:Transplantation, Homologous
D007328:Insulin; D007376:Interleukin-2; D011498:Protein Precursors; D012333:RNA, Messenger; D015847:Interleukin-4; C013737:preproinsulin; D007371:Interferon-gamma; D011384:Proinsulin