Expression of cytokine mRNAs in murine hearts with acute myocarditis caused by coxsackievirus b3.

In murine acute viral myocarditis, natural killer (NK) cells infiltrate the heart first, followed by activated T-cells, which play an important role in the pathogenesis of the myocardial damage. Because of their multipotential effects, cytokines are thought to play a role in the induction and development of these immune processes. To clarify in more detail the precise mechanism of the cytokine networks involved, the expression of various cytokine mRNAs has been investigated in myocardial cells infected with Coxsackievirus B3 (CVB3) in vivo and in vitro by a semiquantitative polymerase chain reaction (PCR) method. Interleukin (IL)-1 alpha, IL-1 beta, IL-6, tumour necrosis factor (TNF)-alpha, and TNF-beta were expressed almost throughout the early phase of virus infection with some variations. IL-2, IL-3, IL-4, IL-10, interferon (IFN)-gamma, granulocyte/macrophage colony stimulating factor (GM-CSF), and IL-2 receptor (IL-2R) were mainly expressed by the infiltrating cells. TNF-alpha, TNF-beta, and IL-1 beta were also expressed partly by the infiltrating cells. T-helper (Th)1-related cytokines (IL-2, IFN-gamma, and TNF-beta) were more strongly expressed than Th2-related cytokines (IL-4 and IL-10) in vivo, indicating that the Th cells which infiltrated the heart and mediated the immune responses in the early phase of acute myocarditis were mainly of Th1-type.