A Morphologic and Immunohistochemical Study of the Bronchus-associated Lymphoid Tissue of Pigs Naturally Infected withMycoplasma hyopneumoniae

Abstract

Abstract. Porcine enzootic pneumonia (PEN), caused by Mycoplasma hyopneumoniae (Mh), has been described in pigs in all geographic areas. The disease is characterized by high morbidity and low mortality rates in intensive swine production systems. A morphologic and immunohistochemical study was done to determine the cellular populations present in lung parenchyma of infected pigs, with special attention to the bronchusassociated lymphoid tissue (BALT). Polyclonal and monoclonal antibodies were used for the detection of antigens of Mh, T lymphocytes (CD3 ϩ , CD4 ϩ , and CD8 ϩ ), IgG ϩ or IgA ϩ lymphocytes, and cells containing lysozyme, S-100 protein, major histocompatibility complex class II antigen or myeloid-histiocyte antigen. Findings in lung tissues associated with Mh infection were catarrhal bronchointerstitial pneumonia, with infiltration of inflammatory cells in the lamina propria of bronchi and bronchioles and alveolar septa. Hyperplasia of mononuclear cells in the BALT areas was the most significant histologic change. The BALT showed a high morphologic and cellular organization. Macrophages and B lymphocytes were the main cellular components of germinal centers. T lymphocytes were primarily located in perifollicular areas of the BALT, lamina propria and within the airway epithelium, and plasma cells containing IgG or IgA at the periphery of the BALT, in the lamina propria of bronchi and bronchioles, in alveolar septa, and around bronchial submucosal glands. The hyperplastic BALT in PEN cases consisted of macrophages, dendritic cells, T and B lymphocytes, and IgG ϩ and IgA ϩ plasma cells. CD4 ϩ cells predominated over CD8 ϩ cells. Local humoral immunity appears to play an important role in the infection.

Nested-PCR for the detection of Mycoplasma hyopneumoniae in bronchial alveolar swabs, frozen tissues and formalin-fixed paraffin-embedded swine lung samples: comparative evaluation with immunohistochemical findings and histological features

“…The cranioventral consolidation observed in the lung samples obtained in this study has also been reported in other studies involving Mycoplasma hyopneumoniae (Sarradel et al 2003, Redondo et al 2009) and can be attributed to the accumulation of mucus and exudates caused by a loss of mucociliary function, increased production of mucus by the globlet cells, bronchoconstriction caused by chemical mediators released by the alveolar macrophages, and the presence of BALT hyperplasia.…”

“…Among the histological ϐindings in the swine lungs, BALT hyperplasia is one of the most indicative of M. hyopneumoniae infection (Sarradel et al 2003, Redondo et al 2009, Hansen et al 2010. The presence of macrophages, neutrophils and alveolar edema is commonly associated with secondary bacterial infection (Redondo et al 2009, Hansen et al 2010.…”

“…Cranioventral consolidation of the lungs is the most speciϐic macroscopic lesion caused by M. hyopneumoniae (Sarradel et al 2003, Ribeiro et al 2004, Redondo et al 2009). Microscopically, hyperplasia of the bronchus-associated lymphoid tissue (BALT) is the particular feature that is most related to this agent (Sarradel et al 2003, Redondo et al 2009).…”

“…Microscopically, hyperplasia of the bronchus-associated lymphoid tissue (BALT) is the particular feature that is most related to this agent (Sarradel et al 2003, Redondo et al 2009). The culture and isolation of M. hyopneumoniae is recognized as the gold standard for the detection of the bacterium because of its high speciϐicity.…”

Pneumonia enzoótica em javalis (Sus scrofa)

“…A pneumonia enzoótica suína, causada primariamente pelo Mycoplasma hyopneumoniae, é uma doença respiratória crônica distribuída mundialmente, e pode afetar 70 a 100% dos animais em um rebanho de suínos (Kwon et al 2002, Sarradel et al 2003. Essa bactéria coloniza a superfície do epitélio respiratório resultando em diminuição e perda da atividade ciliar e degeneração das células epiteliais (Sarradel et al 2003, Thacker 2004.…”