Cytokine mRNA expression profiles in lymphoid tissues of pigs naturally affected by postweaning multisystemic wasting syndrome

Abstract

Fifteen 8-week-old conventional pigs were selected from a farm where pigs were suffering from postweaning multisystemic wasting syndrome (PMWS). Ten of the animals were diseased pigs showing typical signs of PMWS (wasting and respiratory disorders) and positive for infection with porcine circovirus type 2 (PCV2), and the other five animals selected as controls were pen-mate, apparently healthy pigs. Blood samples and lymphoid tissues were taken from each animal for haematological, serological and histopathological studies. Also, cytokine mRNA expression of IL-1beta, IL-2, IL-4, IL-8, IL-10, IL-12p40 and IFN-gamma from inguinal and bronchial lymph nodes, tonsils, spleen and thymus was determined by semi-quantitative RT-PCR. Pigs suffering from PMWS showed severe alterations of haematological parameters such as anaemia, lymphopenia with decrease of CD8(+) and IgM(+) cells, monocytosis and neutrophilia. Also, extensive lymphocyte depletion and altered cytokine mRNA expression patterns were seen in most of the examined lymphoid organs. Those cytokine mRNA alterations were characterized by an overexpression of IL-10 mRNA in thymus and IFN-gamma mRNA in tonsils, and by decreases in the mRNA expression of several cytokines as IL-2 and IL-12p40 in the spleen, IL-4 in tonsils, and IFN-gamma, IL-10, IL-12p40 and IL-4 in inguinal lymph nodes. Also, the IL-10 mRNA overexpression was histologically associated with the thymic depletion and atrophy observed in PMWS pigs. In conclusion, the cytokine mRNA imbalance, specially the increased mRNA levels of IL-10 in the thymus, jointly with the histopathological and haematological disorders, are highly indicative of a T-cell immunosuppression, enhancing the notion that the immune system of PMWS-affected pigs is severely impaired.

Porcine circovirus type 2-induced interleukin-10 modulates recall antigen responses

“…Also, in vitro, PCV2 itself seems to stimulate the production of IL-10 ( Darwich et al, 2003a). Ex vivo, PCV2-infected pigs have increased IL-10 mRNA expression in the thymus (Darwich et al, 2003b). Also, elevated systemic IL-10 mRNA levels have been reported in PMWSaffected pigs (Sipos et al, 2004); however, contradictory results on IL-10 mRNA levels have been described elsewhere (Sipos et al, 2005).…”

Circovirose suína

“…Em condições experimentais, o período de incubação pode chegar a 2-4 semanas (Allan et al 1999a, Balash et al 1999, Harms et al 2001, período no qual o acúmulo de vírus necessário para iniciar a doença é alcançado. Quanto maior a quantidade de antígeno vírico detectada, maior a depleção linfóide , Darwich et al 2002, Chianini et al 2003, Darwich et al 2003.…”

“…A diminuição na expressão de IL-10 (interleucina 10) mRNA tem sido associada à depleção e à atrofia tímica em animais com SDMSD, bem como a diminuição da IL-2 em baço, IL-4 em tonsilas e linfonodos, IL-12p40 em baço e linfonodos inguinais e IFN-ã (interferon-ã) e IL-10 em linfonodos inguinais (Darwich et al 2003). Com relação a citocinas pró-inflamatórias tem sido reportado que os níveis de IL-8 mRNA estão altos em tecidos com lesões leves ou moderadas, com pequena quantidade de vírus, entretanto ela seria baixa em lesões severas (Darwich et al 2003b); outros autores porém não confirmaram esse aspecto, apenas os altos níveis de MCP-1 (Kim & Chae 2003).…”

“…Em porcos com SDMSD, o número de linfócitos está significativamente baixo (especialmente CD8+ e células B) e de monócitos e neutrófilos claramente aumentado, com uma inversão da proporção linfócito/neutrófilo , Darwich et al 2003. Por outro lado, não há alteração no número total de leucócitos.…”

“…Por outro lado, não há alteração no número total de leucócitos. Porcos com SDMSD, geralmente tem anemia normocítica hipocrômica com leve aumento inicial do número de células vermelhas (Darwich et al 2003). O nível de haptoglobina e MAP-pig (proteínas da fase aguda da SDMSD) está aumentado .…”