Intra-Species and Inter-Species Differences in Cytokine Production by Porcine Antigen-Presenting Cells Stimulated by Mycoplasma hyopneumoniae, M. hyorhinis, and M. flocculare

Abstract

<i>Mycoplasma hyorhinis</i> and <i>M. flocculare</i> are commonly co-isolated with <i>M. hyopneumoniae</i> (primary agent of swine enzootic pneumonia) in gross pneumonia-like lesions, but their involvement in the disease process remains unknown. T cells play an immuno-pathological role during mycoplasmal infections. Dendritic cells (DCs) are major antigen-presenting cells involved in T cell activation and differentiation. In this study, we investigated cytokine (IL-6, IL-8, IL-10, IL-12, and TNF-α) production by porcine bone-marrow-derived DCs (BM-DCs) stimulated by <i>M. hyopneumoniae</i>, <i>M. hyorhinis</i>, and/or <i>M. flocculare</i>. Results showed that cytokine production levels were relatively homogenous for all evaluated <i>M. hyopneumoniae</i> strains in contrast to <i>M. hyorhinis</i> and <i>M. flocculare</i> strains. The most noteworthy inter-species differences were the overall (i) lower IL-12 production capacity of <i>M. hyopneumoniae</i>, and (ii) higher TNF-α production capacity of <i>M. flocculare</i>. Co-stimulation of BM-DCs showed that <i>M. hyorhinis</i> dominated the IL-12 production independently of its association with <i>M. hyopneumoniae</i> or <i>M. flocculare</i>. In addition, a decreased BM-DC production of TNF-α was generally observed in the presence of mycoplasma associations. Lastly, <i>M. flocculare</i> association with <i>M. hyopneumoniae</i> increased BM-DC ability to secrete IL-10. A higher cytotoxicity level in BM-DCs stimulated by <i>M. hyorhinis</i> was also observed. Overall, this study demonstrated that the combination of <i>M. hyorhinis</i> or <i>M. flocculare</i> with <i>M. hyopneumoniae</i> may participate to the modulation of the immune response that might affect the final disease outcome.