Polarización TH17 en linfocitos T humanos por células presentadoras de antígeno profesionales

Résumé

The characterization of "type 17" human memory helper T-cells (Th17) and Th1/17 (ie.: IFN e IL-17 dual producers) was published during academic year 2007-08 papers just to starting this Ph.D. Thesis, which revealed that Th17 y Th1/17 frequencies in the circulation were markedly lower than those of Th1 or Th2 cells. They represented ~10% and ~1% of the Th1 blood numbers, respectively. Th1 and Th17 instruction was originally attributed to selective ¿polarization¿ mechanisms driven by professional antigen presenting cells (APC), that were opposed and memorized or developmentally fixed for each Th-type. Thus, Th naïve cells were proposed to develop into Th17 CCR6+ memory cells in secondary lymphoid organs after instruction by classic monocytes (cMo), which have a selective lymph node migration pattern. A paradox in current Th17 activation model is that memory Th17 y Th1/17 frequencies do not increase in the blood of patients suffering several autoimmune diseases with markedly increased CCR6+ Th1/17 and Th17 cell numbers in their lesions, who further show tissue frequencies similar between Th1/17, Th17 and Th1 cells despite their differences in the blood pool. Prior work in the mouse model had facilitated the pathway to define cytokine cocktails implicated in Th17 polarization of naïve T cells in APC-free models, and underlined the relevance of asymmetric cell growth and plasticity between Th types to account for the balance among Th1/Th1/17/Th17 memory effector cells in lesions. Herein we examined a novel mechanism to address whether it may explain the counterintuitive high numbers of CCR6+ Th1/17 and Th17 effector memory T cells in tissue lesions. The Hypothesis was that a non-classic monocyte-dendritic subset (ncMo) termed M-DC8+ after their morphology, that scans inflammed endothelium and migrates to tissue where they encounter Th memory cells which infiltrate tissue lesions in a CCR6-driven way, should instruct into proinflammatory Th-type responses. Predictions from our Hypothesis were an M-C8+ DC-dependent regulation of T-type proliferation favoring asymmetric growth of Th1/17 and Th17 cells directly and/or indirectly through developmental plasticity in Th phenotypes following repolarization in a Th1Th1/17 ¿Th17 precursor-product pathway. DC M-DC8+ and Th memory cells were purified by automated magnetic cells sorting (AutoMACS). The frequencies of individual cells producing IL17, IL-22 and/or IFN within their in generations, and their patterns of expression of T-bet and RORt nuclear factors implicated in Th1 and Th17 commitment was quantitated by Th cell staining with CFSE cell-division tracker and specific antibodies in immunofluorescence and multiplex flowcytometry assays. Cytokine secretion was assessed by multiplex bead immunoassays. Our results showed that CCR6+ Th1, Th17 and Th1/17 memory cells proliferated in a DC M-DC8+-dependent manner, through a mechanism that was accompanied by Th1Th1/17 repolarization driven by augmented RORt transcription factor expression in those cells. All together it accounted for the marked and equilibrated expansion of Th1, Th17 and Th1/17 effector memory subsets. The IL-12/IL-23 balance was key to regulate the above repolarization through T-bet y ROR¿t levels modulation. Our system allowed to investigate the role of cytokines that have been implicated in naïve Th cell polarization in the above proliferation/differentiation mechanisms, and more interestingly to show that it is suitable to address the implication of third party cells in Th17 regulation, ie.: NK reduced IL-17 production. Ex vivo modelization of DC M-DC8+-driven Th memory activation in lesions may contribute to the discovery and assay of novel cellular and molecular targets relevant to control chronic compound proinflammatory Th that implicate Th1, Th17 and Th22 cells, which is also needed to improve our rational to use biological response modifier drugs in inflammation infection, transplantation and cancer.