Differential Expression of Proinflammatory Cytokines in the Lymphoid Organs of Porcine Reproductive and Respiratory Syndrome Virus-Infected Pigs

Porcine reproductive and respiratory syndrome (PRRS) is considered one of the most important diseases in the swine industry. Although several studies have been carried out to elucidate the host immune response evoked against PRRS virus (PRRSV), there are several aspects that still remain unclear. The aim of this study was to determine the expression of IL-1a, IL-6 and TNF-a in the lymphoid organs (mediastinal and retropharyngeal lymph nodes and tonsil) of PRRSV-infected pigs and to determine their correlation with the expression of PRRSV antigen. Proinflammatory cytokine expression was different depending on the body compartment examined. Thus, whereas IL-1a and TNF-a were the main cytokines expressed in the mediastinal lymph node, IL-6 was the most highly expressed cytokine in the retropharyngeal lymph node, and no expression of proinflammatory cytokines was observed in the tonsil. These findings may be related to the impairment of the host immune response evoked after PRRSV infection. Therefore, lymphoid organs and proinflammatory cytokines represent an important target of study for clarifying the immunopathogenesis of PRRS.