Intravenous gamma globulin decreases platelet‐associated IgG and improves transfusion responses in platelet refractory states

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.