[Binding of IgA1 to monocyte/macrophage cell lines (THP-1, U937) in IgA nephropathy--a possible role of O-glycan in the IgA1 molecule].
IgA1 is an exceptional serum glycoprotein because it has O-glycans in the hinge region. It has been observed that the monocyte/macrophages infiltrate within the glomeruli in IgA-N. On the other hand, it is well established that the carbohydrate side chains (N-glycans) of the IgG molecule play a role in the binding of IgG to Fc receptors. Therefore, the binding of IgA1 to monocyte/macrophage cell lines was observed with the aim of clarifying the role of the O-glycan side chains in IgA-N in the initial mechanism of glomerular damage due to the interaction between the O-glycan chains on the IgA1 molecule and infiltrating monocyte/macrophages. Two human myelomonocytic cell lines, THP-1 and U-937, were activated and incubated with separated IgA1 (IgA-N, n = 16; other glomerulonephritides (other GN), n = 15; healthy controls, n = 9). The binding attitude of IgA1 to the cell lines was observed by flow immunofluorometry using a FACScan. FACScan showed that the binding of IgA1 to both of the stimulated monocyte/macrophage cell lines was increased in IgA-N compared to the normal controls and other GN. The binding of IgA1 to THP-1 was partially, but definitely inhibited by adding 100 mM melibiose (19.6 +/- 7.7%) and galactose (13.1 +/- 2.9%), but not glucose (2.9 +/- 2.2%), lactose (4.7 +/- 4.7%) and mannose (3.3 +/- 3.3%). These results suggested that THP-1 had a receptor that recognized the O-glycan in the IgA1 hinge region.(ABSTRACT TRUNCATED AT 250 WORDS)
D002460:Cell Line; D005922:Glomerulonephritis, IGA / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism; D011134:Polysaccharides / Q000502:physiology*; D011961:Receptors, Fc / Q000378:metabolism; D015398:Signal Transduction
D007070:Immunoglobulin A; D011134:Polysaccharides; D011961:Receptors, Fc