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Localization of the guinea pig eosinophil major basic protein to the core of the granule
Abstract:
The localization of the guinea pig eosinophil major basic protein (MBP) within the cell was investigated by the use of immunoelectron microscopy and by isolation of the granule crystalloids. First, by immunoperoxidase electron microscopy, we found that the MBP of eosinophil granules is contained within the crystalloid core of the granule. Specific staining of cores was present when rabbit antiserum to MBP was used as the first stage antibody in a double antibody staining procedure, whereas staining was not seen when normal rabbit serum was used as the first stage antibody. Second, crystalloids were isolated from eosinophil granules by disruption in 0.1% Triton X-100 and centrifugation through a cushion of 50% sucrose. Highly purified core preparations yielded essentially a single band when analyzed by electrophoresis on polyacrylamide gels containing 1% sodium dodecyl sulfate (SDS). The E1%1cm of the core protein was 26.8 +/- 1.0 (X +/- SEM); the E1%1cm for the MBP was 26.3. The core protein could not be distinguished from the MBP by radioimmunoassay (RIA) and essentially all of the protein in the core preparations could be accounted for as MBP. The results indicate that the MBP is contained in the core of the guinea pig eosinophil granule and that it is probably the only protein present in the core.
Insights
Guinea pig eosinophil major basic protein (MBP) is located within the crystalloid core of eosinophil granules. This finding was confirmed through immunoelectron microscopy and protein isolation, identifying MBP as the primary core component.
Area of Science:
- Cell Biology
- Immunology
- Protein Biochemistry
Background:
- Eosinophils are key immune cells involved in parasitic infections and allergic responses.
- The major basic protein (MBP) is a primary granule component of eosinophils, implicated in host defense and tissue damage.
Purpose of the Study:
- To precisely determine the cellular localization of guinea pig eosinophil major basic protein (MBP).
- To characterize the protein composition of eosinophil granule crystalloids.
Main Methods:
- Immunoperoxidase electron microscopy was employed to visualize MBP.
- Eosinophil granule crystalloids were isolated using Triton X-100 and sucrose density gradient centrifugation.
- Polyacrylamide gel electrophoresis (SDS-PAGE) and radioimmunoassay (RIA) were used for protein analysis.
Main Results:
- Immunoelectron microscopy confirmed MBP is localized within the crystalloid core of eosinophil granules.
- Isolated crystalloid preparations yielded a single protein band on SDS-PAGE, consistent with MBP.
- RIA and spectrophotometric analysis indicated that MBP constitutes essentially all of the protein in the crystalloid core.
Conclusions:
- The major basic protein (MBP) is definitively localized to the core of guinea pig eosinophil granules.
- MBP is likely the sole protein component of the eosinophil granule core.