Figure 2.
FcγR-Independent Activity of Human IgG2
(A) Activation of human B cells by ChiLob 7/4 h1 or ChiLob 7/4 h2 plus or minus a 50-fold excess of blocking anti-FcγRII (AT10) F(ab′)2 and/or hFcγRIIB-overexpressing 293F cells (+/− FcγRII) as indicated, assessed by homotypic adhesion (top; bar, 1 mm) and CD23 expression (treated cells, black line; unstimulated cells, gray histogram).
(B) Activation of human B cells by ChiLob 7/4 h1 and ChiLob 7/4 h2 whole IgG, F(ab′)2, or Fab′ for 16 hr at 1 μg/ml assessed by homotypic adhesion (top; bar, 1 mm), CD23 upregulation (middle), and proliferation (bottom). Means and ranges of duplicate samples from one of four experiments.
(C) Proliferation of hCD40 Tg B cells WT or KO for FcγRIIB with various concentrations of the indicated ChiLob 7/4 isotypes determined by [3H]thymidine incorporation (mean and range of duplicates, one of four experiments).
(D) hCD40 Tg mice (n = 3–5) that were FcγR WT, FcγRIIB KO, or common γ chain KO (no activatory FcγR) received OTI cells and then OVA plus the indicated ChiLob 7/4 mAb. Circulating OTI cells were enumerated at day 5. Combined results from two experiments.
(E) hCD40Tg/FcγRIIB KO mice received OTI cells then were immunized with OVA alone (Con) or with 200 μg of ChiLob 7/4 h1 Fab′2 or ChiLob 7/4 h2 Fab′2 i.v. on day 0 followed by 100 μg of Fab′2 on days 1 and 2. Circulating OTI cells on day 5 are shown. Similar results were obtained when mice were given a single 100 μg dose of h2 Fab′2 i.v. (not shown). ∗∗∗p < 0.001, ∗p < 0.05.
See also Figure S2.