Compositional similarity between immunoglobulins binding to asialo-, agalacto-IgA1-Sepharose and those deposited in glomeruli in IgA nephropathy.
BACKGROUND
It has been found that the immunoglobulin A1-binding protein (IgA1-BP) can be separated from human serum using an asialo-, agalacto-IgA1 (aglyco-IgA1)-Sepharose column (13). As the IgA content in IgA1-BP was significantly higher in IgA nephropathy patients than that in other nephropathy patients, the relationship between IgA in IgA1-BP and glomerular deposited IgA was predicted.


METHODS
IgA1-BP was separated from serum using the aglyco-IgA1-Sepharose column and the aglyco-IgA1-HPLC column. A jacalin-agarose column fractionated the IgA. The immunoglobulins were analyzed by the enzyme-linked immunosorbent assay (ELISA).


RESULTS
A rapid separation method of IgA1-BP from serum by the aglyco-IgA1-HPLC column was developed and this column confirmed the reproduction of the IgA1-BP separation. The following similarities between IgA in IgA1-BP and glomerular deposited IgA were detected. A major portion of IgA in IgA1-BP was the IgA1 subclass. The IgA was rich in medium-size IgA and in the jacalin-high-affinity IgA1 fraction. The IgA showed a statistically significant lower kappa/lambda ratio in its light-chain composition than that of serum IgA, i.e. abundance in IgA bearing the lambda light chain. Other immunoglobulin classes (IgG and IgM) in IgA1-BP also exhibited a significantly low kappa/lambda ratio.


CONCLUSIONS
In this experiment, preferential bindings of the IgA1 subclass, the medium-size IgA and the IgA with the lambda light chain to the aglyco-IgA1-column were observed. Based on previous reports concerning aglyco-IgA1 self-aggregation, the interaction of aglyco-IgA1 with matrix proteins and the rat glomerular deposition of artificially deglycosylated IgA1, IgA in IgA1-BP is thought to be partially the same molecule as the IgA deposited on the mesangial matrix in the IgA nephropathy patient.
Takatani
Toru
T
Department of Internal Medicine, Kitasato University, Sagamihara, Japan.
Iwase
Hitoo
H
Itoh
Akihiko
A
Nakamura
Ikuko
I
Hayashi
Miyuki
M
Sakamoto
Hisato
H
Kamata
Kouju
K
Kobayashi
Yutaka
Y
Hiki
Yoshiyuki
Y
Okamoto
Makito
M
Higashihara
Masaaki
M
D005591:Chemical Fractionation; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay; D005922:Glomerulonephritis, IGA / Q000097:blood / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood / Q000737:chemistry* / Q000378:metabolism; D007678:Kidney Glomerulus / Q000276:immunology*; D008222:Lymphokines / Q000097:blood / Q000737:chemistry* / Q000302:isolation & purification; D037121:Plant Lectins; D012685:Sepharose
D007070:Immunoglobulin A; D008222:Lymphokines; D037121:Plant Lectins; C013059:immunoglobulin-binding factors; C043696:jacalin; D012685:Sepharose