Improvement of the calibration curve for IFNγ-measurement. For measurement of IFN-γ levels, the original EIA reagent from Cellestis (circles) was substituted by that of PeliKine Compact human EIA (squares). This resulted in a steeper calibration curve and the use of the whole dynamic range of the photometer. Analytically, this means more accurate result interpretation in the cut-off zone. OD405 nm, optical densities measured at 405 nm.