Intracellular IFN- staining. Intracellular IFN- expression in response to
peptide stimulation was performed as previously described (19, 25). A total of
106 brain-derived monocytes or splenocytes per well were cultured for 5 h at 37°C
in 200 l of RPMI 1640 medium, supplemented with 5% fetal calf serum, 10 U
of human recombinant interleukin-2, and brefeldin A (Golgiplug [1 l/ml];
PharMingen) either with or without peptides. The peptides were used at a
concentration of 1 g/ml. Cells were then stained as described above for surface
expression of CD8 and incubated overnight at 4°C. For intracellular IFN-
staining, cells were then fixed and permeabilized using the Cytofix/Cytosperm kit
(PharMingen) and stained with a fluorescein isothiocyanate-conjugated monoclonal
rat anti-mouse IFN- antibody (clone XMG 1.2; PharMingen). Cells were
washed and then suspended in PBS containing 2% paraformaldehyde and analyzed
by FACSan flow cytometry