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Aeromonas salmonicida Infection Only Moderately Regulates Expression of Factors Contributing to Toll-Like Receptor Signaling but Massively Activates the Cellular and Humoral Branches of Innate Immunity in Rainbow Trout (Oncorhynchus mykiss).

Brietzke A, Korytář T, Jaros J, Köllner B, Goldammer T, Seyfert HM, Rebl A - J Immunol Res (2015)

Bottom Line: In contrast, only the fish-specific tlr22a2 and the downstream factor irak1 featured clearly increased transcript levels, while the mRNA concentrations of many other tlr genes decreased.In conclusion, no specific TLR can be singled out as a dominant receptor for A. salmonicida.The recruitment of cellular factors of innate immunity rather than induced expression of pathogen receptors is hence of key importance for mounting a first immune defense against invading A. salmonicida.

View Article: PubMed Central - PubMed

Affiliation: Leibniz Institute for Farm Animal Biology (FBN), Institute of Genome Biology, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.

ABSTRACT
Toll-like receptors (TLRs) are known to detect a defined spectrum of microbial structures. However, the knowledge about the specificity of teleost Tlr factors for distinct pathogens is limited so far. We measured baseline expression profiles of 18 tlr genes and associated signaling factors in four immune-relevant tissues of rainbow trout Oncorhynchus mykiss. Intraperitoneal injection of a lethal dose of Aeromonas salmonicida subsp. salmonicida induced highly increased levels of cytokine mRNAs during a 72-hour postinfection (hpi) period. In contrast, only the fish-specific tlr22a2 and the downstream factor irak1 featured clearly increased transcript levels, while the mRNA concentrations of many other tlr genes decreased. Flow cytometry quantified cell trafficking after infection indicating a dramatic influx of myeloid cells into the peritoneum and a belated low level immigration of lymphoid cells. T and B lymphocytes were differentiated with RT-qPCR revealing that B lymphocytes emigrated from and T lymphocytes immigrated into head kidney. In conclusion, no specific TLR can be singled out as a dominant receptor for A. salmonicida. The recruitment of cellular factors of innate immunity rather than induced expression of pathogen receptors is hence of key importance for mounting a first immune defense against invading A. salmonicida.

No MeSH data available.


Related in: MedlinePlus

Kinetics of leukocyte recruitment into the peritoneum after infection with A. salmonicida. (a) The total number of leukocytes in the peritoneal fluid in infected trout (filled bars) and PBS-injected controls (open bars) was determined with flow cytometry and is given as mean ± SEM from five fish per time point (ordinate). (b) Differentiation of the number of recruited cells into myeloid cells (square symbols) and lymphocytes (circles). (c) Alteration of the percentage of myeloid cells (square symbols) and lymphocytes (circles) after PBS injection (open symbols) or infection with A. salmonicida (filled symbols) as calculated from the data given in (b). Asterisks denote statistical significance with p < 0.001 (∗∗∗), p < 0.01 (∗∗), and p < 0.05 (∗), compared to controls (0 hpi), assessed with one-way ANOVA, followed by Tukey's post hoc test.
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fig5: Kinetics of leukocyte recruitment into the peritoneum after infection with A. salmonicida. (a) The total number of leukocytes in the peritoneal fluid in infected trout (filled bars) and PBS-injected controls (open bars) was determined with flow cytometry and is given as mean ± SEM from five fish per time point (ordinate). (b) Differentiation of the number of recruited cells into myeloid cells (square symbols) and lymphocytes (circles). (c) Alteration of the percentage of myeloid cells (square symbols) and lymphocytes (circles) after PBS injection (open symbols) or infection with A. salmonicida (filled symbols) as calculated from the data given in (b). Asterisks denote statistical significance with p < 0.001 (∗∗∗), p < 0.01 (∗∗), and p < 0.05 (∗), compared to controls (0 hpi), assessed with one-way ANOVA, followed by Tukey's post hoc test.

Mentions: Activation of the early cellular immune response in the peritoneal cavity, the site of infection, was indicated by a very strong increase in the total number of cells (Figure 5(a)). The number of peritoneal leukocytes increased during the first 12 hpi by >40-fold (p < 0.05). Their number remained on this high level for another 60 h in all infected fish. Only slight and statistically insignificant changes were observed in the control group injected with PBS (<2-fold, p = 0.6).


Aeromonas salmonicida Infection Only Moderately Regulates Expression of Factors Contributing to Toll-Like Receptor Signaling but Massively Activates the Cellular and Humoral Branches of Innate Immunity in Rainbow Trout (Oncorhynchus mykiss).

Brietzke A, Korytář T, Jaros J, Köllner B, Goldammer T, Seyfert HM, Rebl A - J Immunol Res (2015)

Kinetics of leukocyte recruitment into the peritoneum after infection with A. salmonicida. (a) The total number of leukocytes in the peritoneal fluid in infected trout (filled bars) and PBS-injected controls (open bars) was determined with flow cytometry and is given as mean ± SEM from five fish per time point (ordinate). (b) Differentiation of the number of recruited cells into myeloid cells (square symbols) and lymphocytes (circles). (c) Alteration of the percentage of myeloid cells (square symbols) and lymphocytes (circles) after PBS injection (open symbols) or infection with A. salmonicida (filled symbols) as calculated from the data given in (b). Asterisks denote statistical significance with p < 0.001 (∗∗∗), p < 0.01 (∗∗), and p < 0.05 (∗), compared to controls (0 hpi), assessed with one-way ANOVA, followed by Tukey's post hoc test.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
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fig5: Kinetics of leukocyte recruitment into the peritoneum after infection with A. salmonicida. (a) The total number of leukocytes in the peritoneal fluid in infected trout (filled bars) and PBS-injected controls (open bars) was determined with flow cytometry and is given as mean ± SEM from five fish per time point (ordinate). (b) Differentiation of the number of recruited cells into myeloid cells (square symbols) and lymphocytes (circles). (c) Alteration of the percentage of myeloid cells (square symbols) and lymphocytes (circles) after PBS injection (open symbols) or infection with A. salmonicida (filled symbols) as calculated from the data given in (b). Asterisks denote statistical significance with p < 0.001 (∗∗∗), p < 0.01 (∗∗), and p < 0.05 (∗), compared to controls (0 hpi), assessed with one-way ANOVA, followed by Tukey's post hoc test.
Mentions: Activation of the early cellular immune response in the peritoneal cavity, the site of infection, was indicated by a very strong increase in the total number of cells (Figure 5(a)). The number of peritoneal leukocytes increased during the first 12 hpi by >40-fold (p < 0.05). Their number remained on this high level for another 60 h in all infected fish. Only slight and statistically insignificant changes were observed in the control group injected with PBS (<2-fold, p = 0.6).

Bottom Line: In contrast, only the fish-specific tlr22a2 and the downstream factor irak1 featured clearly increased transcript levels, while the mRNA concentrations of many other tlr genes decreased.In conclusion, no specific TLR can be singled out as a dominant receptor for A. salmonicida.The recruitment of cellular factors of innate immunity rather than induced expression of pathogen receptors is hence of key importance for mounting a first immune defense against invading A. salmonicida.

View Article: PubMed Central - PubMed

Affiliation: Leibniz Institute for Farm Animal Biology (FBN), Institute of Genome Biology, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.

ABSTRACT
Toll-like receptors (TLRs) are known to detect a defined spectrum of microbial structures. However, the knowledge about the specificity of teleost Tlr factors for distinct pathogens is limited so far. We measured baseline expression profiles of 18 tlr genes and associated signaling factors in four immune-relevant tissues of rainbow trout Oncorhynchus mykiss. Intraperitoneal injection of a lethal dose of Aeromonas salmonicida subsp. salmonicida induced highly increased levels of cytokine mRNAs during a 72-hour postinfection (hpi) period. In contrast, only the fish-specific tlr22a2 and the downstream factor irak1 featured clearly increased transcript levels, while the mRNA concentrations of many other tlr genes decreased. Flow cytometry quantified cell trafficking after infection indicating a dramatic influx of myeloid cells into the peritoneum and a belated low level immigration of lymphoid cells. T and B lymphocytes were differentiated with RT-qPCR revealing that B lymphocytes emigrated from and T lymphocytes immigrated into head kidney. In conclusion, no specific TLR can be singled out as a dominant receptor for A. salmonicida. The recruitment of cellular factors of innate immunity rather than induced expression of pathogen receptors is hence of key importance for mounting a first immune defense against invading A. salmonicida.

No MeSH data available.


Related in: MedlinePlus