Table 1

D–Lc Enhance Growth and Ig Secretion of Resting B Lymphocytes Activated Through CD40

[3H]TdR uptake (cpm × 10−3)IgG (μg/ml)IgM (μg/ml)
MediumD–LcMediumD–LcIL-2IL-2 + D–Lc
Exp. 1Total B cells     7.3 ± 0.0252.4 ± 0.10.1 ± 0.0523.9 ± 0.90.1 ± 0.0226.8 ± 2.6
Low density     5.6 ± 0.0639.0 ± 2.50.2 ± 0.0510.9 ± 1.20.1 ± 0.0216.6 ± 1.5
High density    10.0 ± 1.656.2 ± 1.70.7 ± 0.0127.5 ± 1.00.2 ± 0.0641.9 ± 5.1
Exp. 2Total B cells   3.5 ± 0.617.3 ± 0.20.5 ± 0.01 6.5 ± 0.90.1 ± 0.02 6.0 ± 2.0
High density IgD+CD38+   3.1 ± 0.615.4 ± 1.70.1 ± 0.01 0.5 ± 0.20.3 ± 0.121.5 ± 5.8
High density IgDCD38   3.5 ± 0.218.9 ± 4.70.1 ± 0.05 9.0 ± 1.20.1 ± 0.05 0.6 ± 0.2
  • D–Lc stimulate differentiation of resting naive and memory B cells activated through their CD40. Highly purified B cells were separated according to their size, using Percoll gradients, into low density B cells (activated B cells) and high density B cells (resting B cells). In experiment 1, 104 B cells were cultured over DC40L L cells in the presence or absence of  D–Lc. For expeirment 2, CD20+ resting B cells (high density) were further separated into IgD+CD38 naive B cells and IgDCD38 memory B cells, using three-color FACS® sorting (as described in Materials and Methods). These cells were dispensed at 5 × 103/well together with 2.5 × 103 CD40L L cells with or without 104 D–Lc. DNA synthesis was assayed after 6 d of coculture, and levels of IgG (in the absence of cytokine) and IgM (in the presence of IL-2) were determined at 15 d (1 experiment representative of 3). No significant B cell proliferation and differentiation was observed in absence of CD40L L cells.