Agalactosyl IgG [Gal(0)] is a glycoform of IgG that is found in normal individuals. Its level is raised in several diseases, including rheumatoid arthritis, tuberculosis and Crohn’s disease. The function of Gal(0) is not yet known. It may play a regulatory role within the immune system, or have some effector function.
Gal(0) levels not only reflect disease activity in rheumatoid arthritis, but are also predictive for disease development. It is conceivable that rheumatoid arthritis, as well as other diseases involving arthritis, increased antibody production and high Gal(0) levels, might be due to an infection with a cell wall-deficient mycobacterium.
There is evidence that interleukin-6 is associated with these diseases. Further research is needed to show whether raised interleukin-6 and Gal(0) are epiphenomena, or whether they are important in the pathogenesis of diseases such as rheumatoid arthritis. In the latter case a new approach to treatment could become possible.
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