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Vol. 19, Issue 2, 701-710, February 2008

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Activation Outcomes Induced in Naïve CD8 T-Cells by Macrophages Primed via "Phagocytic" and Nonphagocytic Pathways

Isabel María Olazabal^*, Noa Beatriz Martín-Cofreces^*, María Mittelbrunn, Gloria Martínez del Hoyo, Balbino Alarcón, and Francisco Sánchez-Madrid^*,

*Servicio de Inmunología, Hospital de la Princesa, Universidad Autónoma de Madrid, 28006 Madrid, Spain; Departamento de Biología Vascular e Inflamación, Centro Nacional de Investigaciones Cardiovasculares (CNIC), 28029 Madrid, Spain; and Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain

Submitted July 10, 2007; Revised November 16, 2007; Accepted November 28, 2007
Monitoring Editor: J. Silvio Gutkind

The array of phagocytic receptors expressed by macrophages make them very efficient at pathogen clearance, and the phagocytic process links innate with adaptive immunity. Primary macrophages modulate antigen cross-presentation and T-cell activation. We assessed ex vivo the putative role of different phagocytic receptors in immune synapse formation with CD8 naïve T-cells from OT-I transgenic mice and compared this with the administration of antigen as a soluble peptide. Macrophages that have phagocytosed antigen induce T-cell microtubule-organizing center and F-actin cytoskeleton relocalization to the contact site, as well as the recruitment of proximal T-cell receptor signals such as activated Vav1 and PKC. At the same doses of loaded antigen (1 µM), "phagocytic" macrophages were more efficient than peptide-antigen–loaded macrophages at forming productive immune synapses with T-cells, as indicated by active T-cell TCR/CD3 conformation, LAT phosphorylation, IL-2 production, and T-cell proliferation. Similar T-cell proliferation efficiency was obtained when low doses of soluble peptide (3–30 nM) were loaded on macrophages. These results suggest that the pathway used for antigen uptake may modulate the antigen density presented on MHC-I, resulting in different signals induced in naïve CD8 T-cells, leading either to CD8 T-cell activation or anergy.

Address correspondence to: Francisco Sánchez-Madrid (fsanchez.hlpr{at}salud.madrid.org)

Abbreviations used: LR, C-type lectin receptor; CR, complement receptor; DC, dendritic cell; IS, immune synapse; MTOC, microtubule-organizing center.