Apoptotic cells in peripheral blood from patients with low serum cobalamin.

Apoptotic leukocytes were found by using ultrastructural and light microscopic techniques to examine peripheral blood in ten of twelve patients with low serum cobalamin (vitamin B12) and rarely in normal controls. A total of 88 apoptotic cells (.14% of total leukocytes) were identified in all the patients. One patient also had apoptotic cells found on a routine blood smear. There was no correlation between the finding of these cells and nuclear hypersegmentation, serum cobalamin levels, serum intrinsic factor antibody, serum methylmalonic acid and homocysteine or the Schilling test. Two patients, however, with the most severe vitamin deficiency did not have increased numbers of apoptotic cells suggesting that these patients had lost the ability to initiate the cell death program.