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Leucocyte beta 1,3 galactosyltransferase activity in IgA nephropathy
A C Allen1, P S Topham, S J Harper
1Department of Nephrology, Leicester General Hospital, UK.
Summary
Reduced galactosylation of IgA1 in IgA nephropathy (IgAN) is linked to lower beta 1,3 galactosyltransferase activity specifically in B cells. This enzyme defect may be a key factor in IgAN pathogenesis.
Area of Science:
- Immunology
- Glycobiology
- Nephrology
Background:
- IgA nephropathy (IgAN) is characterized by reduced O-linked glycan galactosylation in the IgA1 hinge region.
- The specific enzymatic defect causing this abnormality remains unclear.
Purpose of the Study:
- To investigate the activity of beta 1,3 galactosyltransferase, the enzyme responsible for O-linked glycan galactosylation.
- To determine if reduced enzyme activity is present in immune cells of IgAN patients.
Main Methods:
- Assessed beta 1,3 galactosyltransferase activity in T cells, B cells, and monocytes from IgAN patients and controls.
- Used a galactose-acceptor substrate and biotinylated Vicia villosa lectin for measurement.
- Correlated enzyme activity with serum IgA galactosylation levels.
Main Results:
- Beta 1,3 galactosyltransferase activity was significantly lower in B cells of IgAN patients compared to controls.
- No significant difference in enzyme activity was observed in T cells or monocytes.
- A negative correlation was found between B cell enzyme activity and serum IgA galactosylation in IgAN patients.
Conclusions:
- Altered IgA1 O-galactosylation in IgAN is associated with a B cell-specific reduction in beta 1,3 galactosyltransferase activity.
- This enzyme deficiency may represent a fundamental pathogenic mechanism in IgA nephropathy.