Elevated Ca²+ influx-inducing activity toward mast cells in pretransfusion sera from patients who developed transfusion-related adverse reactions.

Background: Type I allergic reactions such as urticaria-like manifestations constitute a large percentage of transfusion-related adverse events. Along with donor factors, patient factors might be involved in these reactions. Sera from some patients with chronic idiopathic urticaria show histamine-releasing activity (HRA). Sera from patients who develop Type I allergic reaction might possess HRA.

Study Design And Methods: Pretransfusion serum samples were collected. Mast cells were cultured from peripheral blood CD34+ cells and mixed with the serum samples. Cells with elevated intracytoplasmic Ca2+ concentrations were monitored using flow cytometry to evaluate Ca2+ influx-inducing activity (CaIA) in serum. The amount of histamine released into the supernatant was measured using an enzyme immunoassay kit to evaluate HRA. In some assays, cells were incubated with pertussis toxin (Ptx).

Results: CaIA values were higher (p < 0.05) in sera from patients with reactions (27.68 ± 20.38 [n = 145]; range, 0.49-84.90) than in sera of patients without reactions (10.70 ± 6.50 [n = 54]; range, 2.67-36.97) and control sera (9.67 ± 5.88 [n = 107]; range, 1.11-25.68). No difference in CaIA was found between patients with (27.38 ± 20.46 [n = 88]) and without (28.38 ± 20.59 [n = 57]) skin manifestations. However, CaIA was higher (p < 0.05) in patients with pure urticaria (mean, 30.58 ± 21.3 [n = 30]; range, 70.43-4.1) than in patients with fever alone (mean, 18.61 ± 14.71 [n = 18]; range, 45.94-3.19). Levels of HRA were higher (p < 0.001) in CaIA-positive sera than in CaIA-negative sera. Both CaIA and HRA were blocked by Ptx.

Conclusion: Elevated CaIA and HRA in pretransfusion sera might be attributable to adverse reactions, especially to urticaria-like manifestation. The Gi protein-coupled receptor complexes on mast cells and its ligand must be involved.