Assuntos
Quimiocina CCL19/genética , Proteínas de Peixes/genética , Salmo salar/genética , Salmo salar/imunologia , Transcrição Gênica , Animais , Quimiocina CCL19/metabolismo , Proteínas de Peixes/metabolismo , Brânquias/imunologia , Rim Cefálico/imunologia , Tecido Linfoide/imunologia , Timo/imunologiaRESUMO
Central and peripheral immune tolerance is together with defense mechanisms a hallmark of all lymphoid tissues. In fish, such tolerance is especially important in the gills, where the intimate contact between gill tissue and the aqueous environment would otherwise lead to continual immune stimulation by innocuous antigens. In this paper, we focus on the expression of genes associated with immune regulation by the interbranchial lymphoid tissue (ILT) in an attempt to understand its role in maintaining immune homeostasis. Both healthy and virus-challenged fish were investigated, and transcript levels were examined from laser-dissected ILT, gills, head kidney and intestine. Lack of Aire expression in the ILT excluded its involvement in central tolerance and any possibility of its being an analogue to the thymus. On the other hand, the ILT appears to participate in peripheral immune tolerance due to its relatively high expression of forkhead box protein 3 (Foxp3) and other genes associated with regulatory T cells (Tregs) and immune suppression.
Assuntos
Região Branquial/fisiologia , Doenças dos Peixes/imunologia , Brânquias/fisiologia , Tecido Linfoide/fisiologia , Salmo salar/imunologia , Linfócitos T Reguladores/imunologia , Viroses/imunologia , Animais , Tolerância Central , Proteínas de Peixes/genética , Proteínas de Peixes/metabolismo , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Homeostase , Terapia de Imunossupressão , Tolerância Periférica , TranscriptomaRESUMO
Previously, our group has shown that the interbranchial lymphoid tissue (ILT) is a distinct structure largely consisting of T cells embedded in a meshwork of epithelial cells, with no direct resemblance to previously described lymphoid tissues. In this study, we aim to focus on the T cell population and the possibility of the ILT being a thymus analog. By characterizing structural responsiveness to Ag challenge, the presence of recombination activating genes, and different T cell-related transcripts, we attempt to further approach the immunological function of the ILT in salmonid gills. In addition to eight healthy individuals, a group of eight infectious salmon anemia virus-challenged fish were included to observe T cell responses related to infection. The results showed reduced size of ILT in the infected group, no expression of RAG-1 and -2, and a high degree of T cell diversity within the ILT. Taking into account that the ILT can be regarded as a strategically located T cell reservoir and possibly an evolutionary forerunner of mammalian MALTs right at the border to the external environment, the alteration in transcription observed may likely represent a shift in the T cell population to optimize local gill defense mechanisms.
Assuntos
Regulação da Expressão Gênica/imunologia , Brânquias/imunologia , Tecido Linfoide/imunologia , Salmo salar/imunologia , Linfócitos T/imunologia , Transcrição Gênica/imunologia , Animais , Proteínas de Ligação a DNA/imunologia , Brânquias/citologia , Proteínas de Homeodomínio/imunologia , Tecido Linfoide/citologia , Linfócitos T/citologiaRESUMO
Previously, it has been assumed that fish lack organized mucosa-associated lymphoid structures. Recently, an interbranchial lymphoid tissue (ILT) was described in salmonid gills at a site with substantial exposure to antigen. In this study, immune responses were examined in gills, mid-kidney and the laser-dissected ILT of Atlantic salmon (Salmo salar L.) infected with infectious salmon anaemia virus (ISAV). A strong innate response was observed in gills and mid-kidney and even in the laser-dissected ILT, despite the fact that no virus could be traced in this tissue. A small delayed increase in IgT transcripts, exclusively in the ILT, could indicate that this tissue has a role as a secondary lymphoid organ with clonal expansion of IgT expressing B-cells. Compared to the other examined tissues, gills displayed the earliest replication of the virus, further supporting this tissue as the main entry route for infection with ISAV.