Inflammatory disorders of the heart are major causes of pediatric morbidity and mortality. Several inflammatory mediators and cell adhesion molecules(CAMs) have been implicated as major contributors to the inflammatory process in various clinical conditions. Using polymerase chain reaction (PCR) analysis, we have previously detected nucleic acid from several virus types within the myocardium of patients with suspected myocarditis (MC) and transplant (Tx) rejection. In this study, we utilized reverse transcription PCR (RT-PCR) to assess mRNA expression of the cytokines tumor necrosis factor-α (TNFα) and interleukin-2 (IL-2), and the CAM, intercellular adhesion molecule-1 (ICAM-1), in those patient groups. Myocardial tissue samples from patients with suspected MC (n=6) or those undergoing Tx rejection surveillance (n=6) were analyzed for the presence of TNFα, IL-2, and ICAM-1 mRNA by gene-specific priming and reverse transcription followed by PCR amplification of cDNA using optimally designed primer pairs. In addition, 6 control samples (explants at time of Tx) were analyzed. Amplification of k-ras, a single copy protooncogene, was performed in all samples to ensure the presence of nucleic acid and to compare its relative abundance. In the MC group (3/6 PCR+ for adenovirus alone, 2/6 for adenovirus and enterovirus, 1/6 for cytomegalovirus), RT-PCR followed by agarose gel electrophoresis of PCR products detected mRNA for ICAM-1 in 4/6 patient samples. Amplification of TNFα and IL-2 was not observed. In contrast, all 6 patient samples from the Tx group, all having histologic evidence of rejection (3/6 mild; 3/6 moderate), demonstrated the presence of TNFα mRNA by RT-PCR, but not ICAM-1 or IL-2. None of the three molecules studied were amplified from control myocardial tissue. These preliminary data show that: (1) RT-PCR may be used for the semiquantitative detection of mRNA expression of the molecules TNFα, IL-2, and ICAM-1 within the myocardium, and (2) Differing patterns of inflammatory mediators may exist depending upon the inciting event (viral infection vs. rejection). Further study of the differential expression of these molecules may lead to improved methods of evaluation and treatment of