Figure 5.

Effects of iron availability on antigen presentation by M1 and M2 cells. (A) M1 (open bars) and M2 (filled bars) macrophages were used to activate MHC class II-restricted T hybridoma cells specific for the nominal antigen ovalbumin (OVA). When indicated, the iron chelator DFO was added. T-cell activation was assessed by IL2 secretion (pg/mL, y axis, see Design and Methods). T-cell activation, as expected, was detectable only when antigen-presenting cells (M1/M2), T cells and the antigen (OVA) were present. DFO did not influence T-cell activation by M1 macrophages, but significantly inhibited T-cell activation by M2 macrophages. (B): M1 and M2 macrophages, cultured in the presence or absence of DFO, were analyzed by flow cytometry after staining with antibodies directed against MHC class II molecules (I-A^b) or against the CD86 co-stimulatory molecule. Filled histograms represent the binding of specific antibodies, whereas open histograms represent the fluorescence background obtained in the presence of isotype-matched control antibodies. Numbers indicate the relative fluorescence intensity (RFI) values, calculated dividing the mean fluorescence intensity obtained in the experimental sample by the one obtained with the relevant control. The results shown are representative of three independent experiments. ** P<0.01, significantly different from control.