A new pathway for antigen uptake triggered by extracellular

JUAN SABATTÉ, ANA CEBALLOS, DIEGO MARTÍNEZ, MÓNICA VERMEULEN, ANALÍA TREVANI, GABRIELA SALAMONE, HORACIO SALOMÓN, JORGE GEFFNER.

Córdoba, Argentina

Congreso; ALAI VII Congreso Latinoamericano de Inmunología; 2005

ALAI

Immature DC capture antigens using two main different mechanisms: receptor-mediated endocytosis and macropinocytosis. Here we showed that extracellular acidosis triggers an alternative mechanism of antigen uptake. DC were obtained from human monocytes cultured for 6 days in the presence of GM-CSF and IL-4. Endocytosis was evaluated by analyzing the uptake of FITC-ovalbumin (FITC-OVA) by flow cytometry and  horseradish peroxidase (HRP) by measuring the enzyme activity in DC lysates. DC were cultured for 1 min at 4oC or 37oC at extracellular pH values of 7.3, 6.5 or 5.5 in the presence of FITC-OVA (250 mg/ml), cells were washed and endocytosis was measured. No endocytosis was observed for DC cultured at pH 7.3 or 6.5: mean fluorescence intensity (MFI) = 8 ± 4 vs 10 ± 3 and 11 ± 2 vs 8 ± 3 for DC cultured at 4oC vs 37oC, at pH 7.3 and 6.5, respectively. By contrast, when DC were cultured at pH 5.5, a dramatic induction of antigen uptake was induced: MFI = 13 ± 5 vs 241 ± 23 (p< 0.001, n=6). Similar results were observed using HRP as an endocytic marker. Transient exposure of DC to pH 5.5 did not result in a loss of cell viability, even when it was evaluated 24 h after treatment. Our results could be relevant to better understand the mechanisms through which DC capture antigens from acidic environments such as the vaginal lumen and solid tumors.