Soluble immunoglobulins sustain the expansion of CAR46/28ζ⁺T cells. Control T cells (□), CAR46ζ⁺ T lymphocytes (▦), and CAR46/28ζ⁺ T lymphocytes (▪) were incubated either with serial dilutions of plasma (A) or purified immunoglobulins (B). After 72 hours, the cells were pulsed with 1 μCi (0.037 MBq) methyl-³[H]thymidine and cultured for an additional 15 hours. Only T cells carrying the CAR46/28ζ proliferate in response to soluble immunoglobulins. Data represent mean ± SD for 3 donors. CAR46ζ⁺ (C) and CAR46/28ζ⁺ (D) T lymphocytes were also cultured for 2 weeks with the addition of plasma or soluble immunoglobulins every 3 days. Only CAR46/28ζ⁺ T cells expanded in presence of plasma or purified immunoglobulins. Data represent mean ± SD for 3 donors.