TABLE 5.

Detection of ch14.18-IL-2 and its components within the intact molecule by various ELISAs^a

ELISA for:	Concn (ng/ml)		% Expected
	Expected	Observed
1A7-IL-2	7,500	6,882	92
IgG	6,250	5,673	91
IL-2	1,250	949	76

^aThree separate experiments were performed with the ch14.18-IL-2 fusion protein (lot 31403) diluted in a sample buffer and tested with all three ELISA methods. The stock fusion protein concentration was standardized by using the IgG1 ELISA. This was diluted with PBS-Tween-milk so that 7,500 ng of fusion protein per ml was tested in the assay. The expected concentrations of IL-2 and ch14.18 components of the fusion protein were based on the calculation that the IL-2 component is one-sixth and the antibody component is five-sixths of the mass of the fusion protein. Observed data are presented as the means of three experiments. Standard deviations are 508 ng/ml for the 1A7-IL-2 ELISA, 32 ng/ml for the IgG ELISA, and 90 ng/ml for the IL-2 ELISA. Percent expected was calculated as the observed concentration/expected concentration × 100.