Figure 4

C3a is a weak MC chemotaxin. Precursor cell-derived murine MC cultured with IL-3 and SCF were treated or not (Ø) with ionomycin (A-C) or Ag (DNP-albumin, following a 24 h preincubation period with IgE anti-DNP) (A, D) for 24 h. Subsequently, in vitro chemotaxis towards different concentrations of C3a (A) or optimal concentrations of C5a (100 ng/ml) and C3a (1000 ng/ml) (B) was measured. In (B), MC were additionally preincubated at 37°C without (Ø) or with C3a to induce receptor desensitization. In (C), MC were labeled with PKH26 and injected i.v. into syngeneic BALB/c mice together with C5a (10 μg) or C3a (50 μg) i.p.. 24 h later, peritoneal cells were harvested and labeled migratory cells identified by FACS analysis. In (D), calcium fluxes in response to C3a (10 μg/ml) or C5a (1 μg/ml) and ionomycin (750 ng/ml) were measured. Mean values (± SEM) of 3 independent experiments each (A-C) and 1 representative experiment of 3 (D) are shown.