Keratan sulfate glycosaminoglycans in murine eosinophil-specific granules

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.