Sensitive diagnosis of cardiac allograft rejection by detection of cytokine transcription in situ.

OBJECTIVE In situ transcription of cytokines which are important in the development of cardiac rejection has not been evaluated for diagnosing rejection. The objective was to evaluate the usefulness of in situ reverse transcriptase polymerase chain reaction (RT-PCR) for sensitive detection of acute cardiac rejection. METHODS We studied interferon (IFN)-gamma and interleukin (IL)-2 expression using immunohistochemistry and in situ RT-PCR in murine cardiac transplant models. Hearts were heterotopically transplanted (BALB/c to C3H/He) and some mice were not treated (n = 23); others were treated with anti-intercellular adhesion molecule (ICAM)-1 and anti-lymphocyte function associated antigen (LFA)-1 monoclonal antibodies (mAbs) (n = 23). Allografts were removed at days 1 to 7. For control, isografts were harvested at day 7 (n = 2). RESULTS Mice without treatment rejected allografts within 7 days, while all mAb-treated recipients accepted allografts for the same period. At day 1, allografts of both groups showed scattered myocardial cell infiltration which increased in non-treated allografts, but remained stable in mAb-treated grafts thereafter. In situ RT-PCR showed that IL-2 and IFN-gamma mRNA positive cells were present in non-treated allografts, while few mRNA positive cells were expressed in infiltrating cells in the mAb-treated allografts (IL-2, day 3: 88.8 +/- 28.3 vs. 7.2 +/- 6.4, p < 0.05, positive cells within 10 fields per section). However, immunohistochemistry could not reveal the difference at day 3. CONCLUSION In situ RT-PCR is a sensitive method for diagnosing acute rejection, and it reveals the characteristics of myocardial infiltrate cells to determine their role in the process of rejection.