Specificity of tolerance induction as evaluated by production of anti–blood group A antibodies. Anti-A (□, ▪) and anti-Gal (○, •) IgG production in KO recipients of 20 × 10⁶ KO lymphocytes that include memory anti-A and memory anti-Gal B cells and 20 × 10⁶ WT lymphocytes (open symbols), or no WT lymphocytes (solid symbols). Anti-Gal activity was measured by absorbance at 492 nm and anti-A activity measured at 405 nm. Data shown are means ± SE (n = 5). Statistical analysis by Student t test indicated significant differences between groups • and ○ at all serum dilutions (P < .05). No significant difference was found between groups ▪ and □.