Concanavalin A (ConA), or media alone for 40 h at 37°C in the presence of 5% CO2. Each
sample was assayed in triplicate. Cells were removed and plates washed twice with double
distilled water, thrice with PBS with 0.01% Tween 20 (PBST), then incubated with 1 µg/mL
biotinylated mouse anti-bovine IFNγ mAb (Mabtech Inc.) for 1 h at room temperature. Plates
were washed four times with PBST and incubated with 0.5 ng/mL streptavidin alkaline
solution (Jackson ImmunoResearch Laboratories Inc., Westgrove, PA) in PBST with 1%
bovine serum albumin (BSA) at room temperature for 45 min. Plates were washed three
times with PBST and twice with PBS. Spots were developed by adding SIGMAFAST
BCIP/NBT (Sigma-Aldrich Corp.) to each well according to the manufacturer’s instructions.
The number of spots in each well was counted using an AID Elispot Reader ELRIFL07
(Autoimmun Diagnostika GMBH, Straßberg, Germany). Numbers of Mhyo-stimulated IFNγ
secreting cells were calculated by subtracting the numbers of spots in media wells from those
in Mhyo stimulated wells. Results were expressed as IFNγ secreting cells per million PBMC.