Soluble immunoglobulins do not impair the capacity of transgenic T cells to eliminate Igκ⁺tumor cells. The inhibitory effect of free immunoglobulins was tested using a standard 4-hour ⁵¹Cr-release assay, in which either T lymphocytes CAR46ζ⁺ (▦) or CAR46/28ζ⁺ (▪) were incubated with Daudi cells (E/T ratio, 20:1) in the presence of serial dilutions of plasma obtained from healthy donors. The top panel illustrates the mean ± SD of residual killing by transgenic T lymphocytes in presence of the plasma for 4 different donors. The bottom panels illustrate the effects of coculturing either control T lymphocytes or CAR46ζ⁺ or CAR46/28ζ⁺ T lymphocytes with Daudi cells at a 10:1 E/T ratio, in complete media (top panels) or in 100% human plasma (bottom panels). After 5 to 7 days of culture, cells were stained with CD3-PerCP and CD19-PE to enumerate CD19⁺ tumor cells. CAR46/28ζ⁺ T lymphocytes were able to prevent the growth of tumor cells even in the presence of human plasma. This is representative of 5 independent experiments.