Distribution of porcine monocytes in different lymphoid tissues and the lungs during experimental Actinobacillus pleuropneumoniae infection and the role of chemokines.

Monocytes play an essential role in the defense against bacterial pathogens. Bone marrow (BM) and peripheral blood (PB) monocytes in pigs consist of the main "steady-state" subpopulations: CD14 hi/CD163-/SLA-DR- and CD14 low/CD163+/SLA-DR+. During inflammation, the subpopulation of "inflammatory" monocytes expressing very high levels of CD163, but lacking the SLA-DR molecule (being CD14 low/CD163+/SLA-DR-) appears in the BM and PB and replaces the CD14 low/CD163+/SLA-DR+ subpopulation. However, current knowledge of monocyte migration into inflamed tissues in pigs is limited. The aim of the present study was to evaluate the distribution of "inflammatory" CD14 low/CD163+/SLA-DR- monocytes during experimental inflammation induced by Actinobacillus pleuropneumoniae (APP) and a possible role for chemokines in attracting "inflammatory" CD14 low/CD163+/SLA-DR- monocytes into the tissues. Monocyte subpopulations were detected by flow cytometry. Chemokines and chemokine receptors were detected by RT-qPCR. The "steady-state" monocytes were found in the BM, PB, spleen and lungs of control pigs. After APP-infection, "inflammatory" monocytes replaced the "steady-state" subpopulation in BM, PB, spleen and moreover, they appeared in an unaffected area, demarcation zone and necrotic area of the lungs and in tracheobronchial lymph nodes. They did not appear in mesenteric lymph nodes. Levels of mRNA for various chemokines with their appropriate receptors were found to be elevated in BM (CCL3-CCR1/CCR5, CCL8-CCR2/CCR5, CCL19-CCR7), necrotic area of the lungs (CCL3-CCR1, CCL5-CCR1/CCR3, CCL11-CCR3, CCL22/CCR4) and tracheobronchial lymph nodes (CCL3-CCR1) and therefore they could play a role in attracting monocytes into inflamed tissues. In conclusion, "inflammatory" monocytes appear in different lymphoid tissues and the lungs after APP infection in pigs. Various chemokines could drive this process.

Interleukin-17 in veterinary animal species and its role in various diseases: a review.

Interleukin 17 (IL-17) as one of the pro-inflammatory cytokines is a very important player in the immune response to many pathogens and seems to play a role also in certain chronic and autoimmune diseases. Many studies showing the importance of this cytokine were conducted on murine models and human patients. In recent years, some experiments with other animals in which interleukin-17 was measured were carried out. This review is focused on the findings that have been observed and described in important veterinary species of animals.

CD4+ and γδTCR+ T lymphocytes are sources of interleukin-17 in swine.

In the veterinary field, only limited information is available about interleukin-17A (IL-17), despite the fact that this cytokine plays an important role during pro-inflammatory immune responses and induces the production of chemotactic factors for neutrophils. The aim of this study was to characterize porcine IL-17-producing cells. We tested the cross-reactivity of five anti-human IL-17 monoclonal antibodies because such antibodies against porcine IL-17 are currently unavailable. Whole blood cells (WBCs) were stimulated with phorbol-myristate-acetate (PMA) and ionomycin and subsequently analyzed by flow cytometry. The antibody clone SCPL1362 was found to cross-react with porcine IL-17, whereas the other four antibodies tested did not recognize this cytokine. Using this antibody, we characterized porcine WBC-secreting IL-17 after PMA and ionomycin stimulation. All IL-17-producing WBCs were positive for the T lymphocyte marker CD3. Myeloid cells (CD172α(+)) and B lymphocytes (CD79α(+)) were IL-17 negative. The major subset of IL-17 positive T lymphocytes was the CD4(+) lymphocytes (about 60% of all IL-17 positive WBCs). The remaining IL-17 positive WBCs were γδTCR(+) lymphocytes. CD8 positive and CD8 negative cells were found within both CD4(+) and γδTCR(+) cells producing the cytokine. Moreover, IL-17 positive cells were mostly CD45RA negative, therefore activated cells or memory cells. Flow cytometry data were confirmed using sorted cells. Both sorted CD4(+) and γδTCR(+) cells produced IL-17 at mRNA level after PMA and ionomycin stimulation while double negative CD4(-)γδTCR(-) cells were negative for IL-17. We can conclude that only two subpopulations of porcine WBCs are sources of IL-17 after non-specific stimulation: CD3(+)CD4(+) and CD3(+)γδTCR(+).