Co⁶⁰ Vitamin B₁₂ Binding Capacity of Human Leukocytes

1. Mature neutrophilic leukocytes show the highest Co⁶⁰B₁₂ binding capacity.

2. Less mature granulocytes, "blast" forms and eosinophils have little or no Co⁶⁰B₁₂ binding capacity.

3. Disintegrated mature leukocytes from chronic myelocytic leukemia and polycythemia vera show higher B₁₂ binding capacity than intact cells.

4. Mature leukocytes from patients with chronic myelocytic leukemia and polycythemia vera show a two-phase B₁₂ curve suggesting specific and nonspecific binding, similar to that observed in human serum.

5. Disintegration products from mature neutrophilic leukocytes probably contribute largely to increased B₁₂ binding capacity of serum in chronic myelocytic leukemia and polycythemia vera.