Cobalamin (vitamin B12) and B12 binding proteins in hypereosinophilic
syndromes and secondary eosinophilia
J Zittoun, JP Farcet, J Marquet, C Sultan and R Zittoun
Serum cobalamin (vitamin B12) and unsaturated B12 binding capacity (UBBC)
have been measured in 24 cases of hypereosinophilia: 16 were cases of
hypereosinophilic syndrome (HES) and 8 of secondary eosinophilia. The two
groups were similar with respect to absolute eosinophil counts. Serum
cobalamin and UBBC were found to be markedly increased in most cases of HES
and normal in secondary eosinophilia. This elevation of UBBC was mainly
related to the increase of R binders (transcobalamins I and III). The
elevated serum cobalamin and R binders in HES were due neither to a higher
intracellular content of R binders nor to an increased release of these
binders from eosinophils of HES. Pure fractions of eosinophils obtained
from HES and secondary eosinophilia did not exhibit any difference in
vitamin B12 binders. On the other hand, neutrophil-rich fractions from the
same patients showed a higher content of intracellular B12 binding proteins
than pure eosinophil fractions, irrespective of the cause of eosinophilia.
These findings suggest that the increased serum vitamin B12 and UBBC could
reflect an expanded pool of both eosinophils and neutrophils in HES and,
thus, provide an additional argument for the inclusion of this syndrome in
the group of myeloproliferative disorders.
Volume 63,
Issue 4,
pp. 779-783,
04/01/1984
Copyright © 1984 by The American Society of Hematology
