• Platelet-associated IgG;
  • platelet refractoriness;
  • immunoglobulin therapy


In an attempt to improve platelet transfusion responses, intravenous immunoglobulin (IV-IgG) was administered to 19 patients who were refractory to random and best available HLA-matched platelets. A response to IV-IgG was defined as two or more successive transfusions of HLA-matched products that provided recoveries greater than 30%. Thirteen of 19 (68%) patients responded to therapy at a median time of 7 days after initiation of IV-IgG (range = 2–17). Baseline platelet associated IgG levels (PaIgG) were elevated in both the responders (61.6 ± 76.2) (mean ± SD) and the non-responders (47.0 ± 46.3 fg/plt). Post-therapy, PaIgG levels remained unchanged in the nonresponders but were decreased significantly (p = 0.05) to 11.1 ± 6.2 fg/plt in the responders. The latter levels were similar to those (11.6 ± 8.2 fg/plt) measured in a series of 36 transfusion responsive patients. This apparent decline in PaIgG was not explained by differences in lymphocytotoxic antibodies (LCT-Ab) after therapy. Moreover, a high degree of alloimmunization was associated with a poorer response to IgG. Only two of eight patients with LCT panel-reactive antibody (PRA) of > 85% were responders. By contrast, improved transfusion outcomes were seen uniformly in patients with PRA ≦ 85%. Improved recoveries were obtained using LCT-Ab compatible but not incompatible platelets. The median increment (% predicted) with compatible platelets before therapy was 6.0 ± 9.9 (SD). Post-IgG, median recoveries were 37.0 ± 31.2 percent, P < 0.001. These findings suggest that IV-IgG may alter destructive mechanisms that affect the survival of compatible platelets in refractory patients.