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Eosinophil granule proteins in peripheral blood granulocytes
R I Abu-Ghazaleh1, S L Dunnette, D A Loegering
1Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905.
Journal of Leukocyte Biology
|December 1, 1992
Summary
Eosinophils primarily contain four cationic proteins: major basic protein (MBP), eosinophil-derived neurotoxin (EDN), eosinophil cationic protein (ECP), and eosinophil peroxidase (EPO). While mainly found in eosinophils, these proteins also show varying presence in basophils and neutrophils.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Eosinophils are key immune cells involved in allergic responses and defense against parasites.
- They contain a repertoire of cationic proteins with diverse functions.
- Understanding the distribution of these proteins is crucial for elucidating eosinophil-specific functions and potential roles in other granulocytes.
Purpose of the Study:
- To quantify the concentrations of four major cationic proteins in human granulocytes.
- To determine if these proteins are specific to eosinophils.
- To investigate the optimal lysis conditions for protein recovery.
Main Methods:
- Human granulocytes were isolated and lysed using various methods.
- Specific radioimmunoassays were employed to measure the concentrations of MBP, EDN, ECP, and EPO.
- Protein recovery was optimized by testing different lysis pH conditions.
Main Results:
- Maximal recovery of MBP was achieved at pH 2, while EDN, ECP, and EPO recovery peaked at pH 5.6.
- Concentrations per 10^6 eosinophils were determined: MBP (8,982 ng), EDN (3,283 ng), ECP (5,269 ng), and EPO (12,174 ng).
- Basophils and neutrophils contained lower, but detectable, amounts of these cationic proteins, indicating some cross-granulocyte expression.
Conclusions:
- The four principal cationic proteins are predominantly expressed in eosinophils.
- Significant levels of MBP, EDN, ECP, and EPO are found in eosinophils.
- While primarily eosinophil-specific, these proteins are also present in basophils and neutrophils, suggesting broader functional implications.