Human T cell IgD receptors react with O‐glycans on both human IgD and IgA1

• Published in: European journal of immunology Vol. 28; no. 8; pp. 2366 - 2372
• Main Authors: Swenson, Christina D., Patel, Thakor, Parekh, Raj B., Tamma, S. M. Lakshmi, Coico, Richard F., Thorbecke, G. Jeanette, Amin, Ashok R.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY‐VCH Verlag GmbH 01.08.1998
• Subjects: Animals; Binding Sites; Carbohydrate Conformation; Carbohydrate Sequence; Disaccharides - chemistry; Disaccharides - metabolism; Fcα receptor; Humans; IgA1; IgD receptor; Immunoglobulin A - chemistry; Immunoglobulin A - metabolism; Immunoglobulin D - chemistry; Immunoglobulin D - metabolism; In Vitro Techniques; Mice; O‐glycan; Polysaccharides - chemistry; Polysaccharides - metabolism; Receptors, Fc - metabolism; T cell; T-Lymphocytes - immunology
• ISSN: 0014-2980; 1521-4141
• DOI: 10.1002/(SICI)1521-4141(199808)28:08<2366::AID-IMMU2366>3.0.CO;2-D

Previous studies on murine T cell IgD‐R have shown that these receptors recognize N‐glycans of murine IgD, and not of other Ig isotypes. We have now studied the specificity of IgD‐R on human T cells. Human IgD digested with proteinase K to fragments of < 5 kDa inhibit the ability of T cells to form rosettes with IgD‐coated ox erythrocytes. The same amount of digested IgG does not. We tested all the human Ig isotypes: IgG1, −2, −3, −4, IgA2, IgE and IgM fail to inhibit significantly at 20 μg/assay. However, IgA1 is as effective as IgD itself, showing approximately 60 % and 80 % inhibition at 5 μg and 10 μg/assay. Human IgA1 and IgD both contain Gal‐1 → 3‐GalNac‐rich O‐linked glycans, and on this basis are both bound to ricin and jacalin. The O‐linked glycans may therefore also represent the common moiety binding to IgD‐R. Disaccharides Gal‐1 → 3‐GalNac, and Gal‐1 → 4‐Glc at 10 μg/assay blocked IgD rosetting while Gal‐1 → 6‐Glc did not. We conclude that the human IgD‐R is a lectin, differing from the murine IgD‐R in that it has both IgA1 and IgD as ligands.