Impaired IgE/antigen-mediated degranulation of PigA-deficient BMMCs. BMMCs were (A) sensitized with IgE anti-DNP, followed by challenge with various concentrations of DNP-BSA for 1 hour, or (B) activated with the nonspecific degranulation stimulus compound 48/80. Degranulation of the cells was expressed as the percentage specific release of β-hexosaminidase into the supernatant relative to the total cell content. In the absence of IgE sensitization, the mean specific β-hexosaminidase release was below 3% for both control and PigA-deficient BMMC at either concentration of DNP-BSA tested (not shown). Filled bars: littermate control BMMC; open bars: PigA-deficient BMMC. Results represent mean ± SEM of at least 3 experiments; asterisks indicate significant difference (P < .05) with control cells.