Pathologic studies in lymph nodes of pigs infected with porcine circovirus type 2, porcine reproductive and respiratory syndrome virus

Porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) have been suspected to have immunosuppressive effects on pigs.To investigate the correlation between these virus infection and the lesions of lymph nodes including sub-mandibular and inguinal lymph node, 44 pigs (PCV2 single, n = 14; PRRSV single, n = 10; PCV2/PRRSV, n = 14; negative control, n = 6) were examined by histopathology and immunohistochemistry. Histopathologically, granulomatous lymphadenitis characterized by lymphoid depletion with histiocytic cells infiltration was observed in PCV-2 single and PCV-2/PRRSV group.Immunohistochemically, there were significant reduction of B and T lymphocytes in lymph nodes of these groups, while the number of macrophages was increased.In only PRRSV infected group, germinal center hypertrophy and lymphoid necrosis were observed.Immunohistochemically, the number of CD3+ T lymphocytes was slightly increased.Severe lymphocytic depletion in PCV-2 infection-related lymph nodes might be associated with producing immunocompromised state in pig.Comparing with PCV-2 infected group, PRRSV produced minor effects on the changes in immune cell population in the lymph nodes of pigs.PRRSV may increase susceptibility of the disease in pigs by disruption of the first defense lines in target organs, such as the alveolar macrophages in lungs.