Antibody to Transcobalamin II and B₁₂ Binding Capacity in Patients Treated With Hydroxocobalamin

Thirty-two patients treated for B₁₂ deficiency with one or two initial depot series of five i.m. injections of 1 mg hydroxocobalamin on alternate days followed by i.m. injection of 1 mg hydroxocobalamin every third month for maintenance therapy were examined after more than 2 yr of treatment. Antibody to TC II demonstrable after agar gel electrophoresis was detected in 5 of 12 patients given two depot series 1-3 mo apart, while antibody to TC II detectable only after the more sensitive immunoelectrophoresis occurred in 2 of 20 patients given one initial depot series or two series 6 or 12 mo apart. No anti-TC II was observed in serum from untreated patients with pernicious anemia.