Injury induces alterations in T-cell NFκB and AP-1 activation

The immune dysfunction that occurs after severe injury involves major changes in T-cell-mediated immunity resulting in suppressed T-helper 1 (Th1) type responses and increased or persistent T-helper 2 (Th2) type cytokine production. Since little is known about what signaling pathways are responsible for this injury-induced phenotypic shift in T-cells, we undertook this study to address the molecular basis for injury effects on T-helper cell subset cytokine expression. Experiments were designed to test whether diminished IL-2 gene expression after thermal injury coincided with changes in the induction of IL-2 gene regulatory transcription factors. Electrophoretic mobility shift assays (EMSA) were used to screen for nuclear expression of changes of the IL-2 gene transcription factors. Our findings revealed that changes in mitogen-stimulated T-cell AP-1 and NFKB factor activation correlated directly with defective mitogen-induced IL-2 mRNA expression. We determined that there was a loss of nuclear AP-1 activation and changes in NFKB factor activation at 9 days after injury. T-cell nuclear extracts prepared from sham injured mice showed induction of NFKB2 (p52) and RelA (p65) containing NFKB EMSA complexes, while we detected no RelA or NFKB2 in EMSA complexes using T-cell nuclear extracts prepared from burn injured mice. Instead, these NFKB EMSA complexes contained mostly NFκB1 (p50). Western immunoblot analysis confirmed defective nuclear RelA translocation. Taken together, these results indicate that T-cell NFKB and AP-1 activation pathways may be involved in the injury-induced changes in T-cell cytokine production and the immune deviation that occurs after injury.