T-lymphocyte phenotype and function triggered by Aggregatibacter actinomycetemcomitans is serotype-dependent.

BACKGROUND AND OBJECTIVE: Based on lipopolysaccharide (LPS) antigenicity, different Aggregatibacter actinomycetemcomitans serotypes have been described. Serotype b strains have demonstrated a stronger capacity to trigger cytokine production on dendritic cells (DCs). As DCs regulate the development of T-lymphocyte lineages, the objective of this investigation was to study the response of T lymphocytes after being stimulated with autologous DCs primed with different bacterial strains belonging to the most prevalent serotypes of A. actinomycetemcomitans in humans: a-c. MATERIAL AND METHODS: Human DCs were primed with increasing multiplicity of infection (10(-1) -10(2) ) or the purified LPS (10-50 ng/mL) of A. actinomycetemcomitans serotypes a-c and then used to stimulate autologous naïve CD4(+) T lymphocytes. The T-helper (Th) type 1, Th2, Th17 and T-regulatory transcription factors T-bet, GATA-3, RORC2 and Foxp3, which are the master-switch genes implied in their specific differentiation, as well as T-cell phenotype-specific cytokine patterns were quantified by real-time reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. In addition, the intracellular expression of T-bet/interferon-γ, GATA-3/interleukin-4, RORC2/interleukin-17A and Foxp3/transforming growth factor-ß1 was analysed by double staining and flow cytometry. RESULTS: All the A. actinomycetemcomitans serotypes led to T-lymphocyte activation; however, when T lymphocytes were stimulated with DCs primed with the A. actinomycetemcomitans serotype b strain or their purified LPS, higher levels of Th1- and Th17-associated transcription factors and cytokines were detected compared with similar experiments with the other serotypes. CONCLUSION: These results demonstrate that serotype b of A. actinomycetemcomitans has a higher capacity of trigger Th1 and Th17 phenotype and function and it was demonstrated that their LPS is a more potent immunogen compared with the other serotypes.

Variabilidad de la síntesis de citoquinas por células dendríticas humanas estimuladas con los distintos serotipos de Aggregatibacter actinomycetecomitans / Variability in the cytokine synthesis by human dendritic cells in response to different Aggregatibacter actinomycetemcomitans serotypes

Objetivo: Sobre la base de la antigenicidad del polisacárido O del LPS, en A. actinomycetemcomitans se describen distintos serotipos bacterianos y entre ellos se ha especulado una patogenicidad e inmunogenicidad diferente. El objetivo de este trabajo es analizar las diferencias en la síntesis de citoquinas producidas por células dendríticas cuando son estimuladas con los distintos serotipos de A. actinomycetemcomitans. Metodología: Células dendríticas diferenciadas a partir de monocitos circulantes periféricos humanos fueron estimuladas a MOIs=10-1-10-2 con los serotipos a, b y c de A. Actinomycetemcomitans. Mediante PCR y ELISA se evaluaron los niveles de expresión y secreción de citoquinas. Resultados: En las células dendríticas, la producción de citoquinas fue diferente ante los distintos serotipos de A. actinomycetemcomitans, con mayores niveles de secreción de IL-1beta, IL-6, IL-12, IL-23, IFN-gamma y TNF-alfa cuando el microorganismo estimulante fue la cepa ATCC® 43718™ (serotipo b). Conclusión: El serotipo b de A. actinomycetemcomitans posee un mayor potencial inmuno-estimulador de células dendríticas comparado con los otros serotipos bacterianos y potencialmente contribuiría a inducir un patrón de respuesta inmune tipo Th1 y/o Th17 durante las periodontitis.

Objective: A. actinomycetemcomitans expresses a number of virulence factors that contribute to direct tissue damage and, based on the antigenicity of LPS O-polysaccharide, distinct serotypes have been described. The aim of this study was to determine the pattern of cytokine expression and secretion on dendritic cells stimulated with A. actinomycetemcomitans serotypes a, b and c. Methods: Using different multiplicity of infections of the serotypes a, b, and c of A. actinomycetemcomitans, the mRNA expression and secretion levels for cytokines IL-1beta, IL-5, IL-6, IL-10, IL-12, IL-23, TNF-alpha, and IFN-gamma were determined in stimulated dendritic cells using PCR and ELISA. Results: A dose-dependent increase in the secretion levels for IL-1beta, IL-5, IL-6, IL-10, IL-12, IL-23, TNF-alpha, and IFN-gamma was elicited on dendritic cells following stimulation with each of the serotypes of A. actinomycetemcomitans. In addition, A. actinomycetemcomitans serotype b (ATCC® 43718™) induced higher levels of IL-1beta, IL-6, IL-12, IL-23, IFN-gamma y TNF-alpha compared with the other strains. Conclusion: These data demonstrate that the distinct A. actinomycetemcomitans LPS O-polysaccharide serotypes induce both quantitative and qualitative differences in the dendritic cell response. Furthermore, the observed dendritic cell response to A. actinomycetemcomitans b serotype was characteristic of a Th1 and Th17 pattern of cytokine expression.