We examined the presence of sialyl glycoconjugates in specific granules fro
m murine bone marrow eosinophils. Lectin cytochemistry using Maackia amuren
sis lectin II (MAL II) specific for sialyl alpha-2,3 galactose residues dem
onstrated positive labeling in both immature and mature specific granules.
Pretreatment with Clostridium neuraminidase or keratanase II eliminated the
positive labeling of MAL II in the specific granules. High iron diamine-th
iocarbohydrazide-silver proteinate physical development (HID-TCH-SP-PD) sta
ining, which is specific for sulfated glycoconjugates, also positively labe
led immature specific granules lacking crystalloids but not mature granules
with crystalloids. Pretreatment with a combination of chondroitinase ABC a
nd keratanase, or a combination of chondroitinase ABC and keratanase II, el
iminated the positive labeling obtained with HID-TCH-SP-PD. These results i
ndicate that the sialyl residues detected by MAL II are expressed as termin
al sugar residues of keratan sulfate proteoglycan, which appears to be of t
he corneal type in view of its sensitivity to keratanase and keratanase II.