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CD97 isoform expression in leukocytes
1Faculty of Biosciences, Pharmaceutics and Psychology, University of Leipzig, Germany.
Insights
The study found that different forms of the CD97 antigen (isoforms) are expressed in leukocytes, but their levels do not significantly change with stimulation. This suggests CD97 isoform expression doesn't regulate CD97's adhesion to CD55.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- The leukocyte CD97 antigen exists in multiple isoforms, each with potentially different adhesive capacities, particularly in interactions with CD55.
- Previous research suggested that varying expression of CD97 isoforms might influence its binding to CD55.
Purpose of the Study:
- To investigate the coexpression patterns of CD97 isoforms in various human leukocytes.
- To determine if differential expression or regulation of CD97 isoforms correlates with CD97's adhesive function towards CD55.
Main Methods:
- Quantitative analysis of CD97 isoform mRNA levels in different cell types (leukocytes, U 937 cells, monocytes, lymphocytes).
- Assessment of CD97 isoform expression changes following stimulation (PMA, interferon-gamma) and cross-linking.
- Correlation analysis between CD97 mRNA levels and surface protein density.
Main Results:
- All three studied CD97 isoforms (CD97 (EGF 1,2,5), CD97 (EGF 1,2,3,5), and CD97 (EGF 1,2,3,4,5)) were coexpressed in leukocytes, with CD97 (EGF 1,2,5) being predominant.
- Expression levels of CD97 isoforms showed only minor variations across most cell types and were not significantly altered by stimulation or in rheumatoid arthritis synovial T cells.
- CD97 mRNA levels did not consistently correlate with the density of CD97 protein on the cell surface.
Conclusions:
- Differential expression of CD97 isoforms is unlikely to be the primary mechanism regulating the adhesive interaction between CD97 and CD55.
- CD97's adhesive activity towards CD55 appears to be independent of the specific isoform expressed.
Abstract:
Different adhesive capacity in interactions with CD55 has been ascribed to the isoforms of the leukocyte CD97 antigen, CD97 (EGF 1,2,5), CD97 (EGF 1,2,3,5), and CD97 (EGF 1,2,3,4,5). In the study, coexpression of the three CD97 isoforms and predominance of CD97 (EGF 1,2,5) transcripts in leukocytes are demonstrated. The contribution of CD97 (EGF 1,2,3,5) and CD97 (EGF 1,2,3,4,5) to total CD97 levels varied among most cell types only slightly, although relatively higher mRNA levels of both isoforms were detected in U 937 cells and monocytes. In peripheral blood lymphocytes, CD97 isoforms did not show clear variation after PMA stimulation and were down-regulated equally after CD97 cross-linking. Moreover, the CD97 isoform pattern was not altered in monocytes after interferon-gamma stimulation and in synovial T cells from patients with rheumatoid arthritis. CD97 mRNA levels did not necessarily correspond to CD97 surface density. The findings suggest that adhesive activity of CD97 toward CD55 is unlikely to be regulated by differential CD97 isoform expression.