Background: CD40-activated B lymphocytes have been used successfully as potent APC for the induction of T-cell responses. However, the 3T3-CD40L cell line, regularly used for engagement of CD40 on the B-cell surface, is a potential source of xenoantigens. This may affect the specificity of T cells stimulated with CD40-activated B cells, especially when generation of T-cell lines specific for endogenously processed Ag is desired.
Methods: To develop a system that allows efficient expansion of B cells in the absence of sources of xenoantigens, we created a human 293-CD40L-sCD40L cell line that produces soluble CD40L and expresses CD40L on the cell surface. B cells from patients with hematologic malignancies were expanded on the 293-CD40L-sCD40L cells and used for stimulation of either naive or in vivo primed donor T cells in three HLA-identical patient-donor combinations.
Results: The 293-CD40L-sCD40L cell line was able to stimulate B-cell growth with an efficiency superior to that of the commonly used 3T3-CD40L cell line. In all cases T-cell lines and, subsequently, T-cell clones were generated that showed reactivity against patient and not donor B cells, suggesting their specificity for minor histocompatibility antigens (mHAg).
Discussion: B cells activated with GMP grade 293-CD40L-sCD40L can be used in a variety of applications. In particular, they may be suitable for ex vivo stimulation of T cells prior to donor lymphocyte infusion (DLI), which may enhance its graft versus leukemia (GvL) effect.