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A carbohydrate neoepitope that is up‐regulated on human mononuclear leucocytes by neuraminidase treatment or by cellular activation
Author(s) -
Quinn Mark T.,
Swain Steve D.,
Parkos Charles A.,
Jutila Kathryn L.,
Siemsen Daniel W.,
Kurk Sandra L.,
Jesaitis Algirdas J.,
Jutila Mark A.
Publication year - 2001
Publication title -
immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.297
H-Index - 133
eISSN - 1365-2567
pISSN - 0019-2805
DOI - 10.1046/j.1365-2567.2001.01300.x
Subject(s) - epitope , neuraminidase , monoclonal antibody , biology , microbiology and biotechnology , antigen , peripheral blood mononuclear cell , sialidase , antibody , immunology , biochemistry , virus , in vitro
Summary The expression of cell‐surface antigens can delineate specific leucocyte developmental or functional stages. For example, certain membrane glycoproteins are expressed selectively on leucocyte subsets only after activation. Leucocyte activation can also induce changes in carbohydrate epitopes expressed on surface antigens. In the present studies, we report on a novel monoclonal immunoglobulin M antibody (mAb 13.22) that recognizes a unique carbohydrate epitope expressed on human leucocyte membrane proteins. Characterization of mAb 13.22 specificity by immunoblotting showed that it recognized proteins of MW ∼95 000 and 150 000, including both CD18 and CD11b. The mAb 13.22 epitope was removed by N ‐glycosidase F but not by endoglycosidase H or fucosidase, demonstrating that it is an N‐linked carbohydrate antigen. Interestingly, immunoblot staining was enhanced after neuraminidase treatment, suggesting that the antibody epitope might also be partially masked by sialic acid. In resting leucocytes, the mAb 13.22 antigen was expressed strongly on neutrophils, while dull staining was present on monocytes, and no lymphocyte staining was observed. In marked contrast, treatment of leucocytes with neuraminidase resulted in exposure of a mAb 13.22 neoepitope on a subset of lymphocytes (primarily T lymphocytes and natural killer cells) as well as up‐regulated staining more than 18‐fold on monocytes. Activation of lymphocytes in culture with phytohaemagglutinin or concanavalin A also unmasked the mAb 13.22 neoepitope on ∼37% of the CD45RO + lymphocytes. Furthermore, analysis of leucocytes collected from the synovial fluid of patients with rheumatoid arthritis showed that ∼18% of the lymphocytes present expressed the mAb 13.22 neoepitope. Taken together, our results suggest that the mAb 13.22 carbohydrate neoepitope could represent a physiologically relevant marker that is up‐regulated on leucocyte subsets during the inflammatory response.