Identification and purification of cytolytic antibodies directed against O-acetylated sialic acid in childhood acute lymphoblastic leukemia.
Sialic acids typically present as terminal sugars of oligo-saccharides are reported to be modified by O-acetylation at the C-9 position on lymphoblasts of childhood acute lymphoblastic leukemia (ALL) patients (Sinha et al., 1999a, Leukaemia, 13, 119-125). We now report high titers of IgG antibodies directed against O-acetylated derivatives of sialic acids (O-AcSA) in serum of ALL patients. These antibodies were purified using bovine submaxillary mucin (BSM) and the IgG distribution was confined to IgG(1)and IgG(2)subclasses; their binding was totally abolished with de-O-acetylation confirming their specificity towards O-AcSA determinants. Flow cytometry demonstrated binding of these antibody fractions to peripheral blood mononuclear cells (PBMC) of both T- and B-ALL patients having increased cell surface 9-O-AcSA determinants. Western blotting of membranes derived from PBMC of ALL patients confirmed binding of the antibody to O-acetylated sialoglycoconjugates corresponding to 144, 135, 120, 90, and 36 kDa whereas binding to PBMC from normal individuals corresponded to 144 and 36 kDa. Specificity of the antibody fraction towards 9-O-AcSA was substantiated by hemagglutination and hemagglutination-inhibition assays. The antibody purified from ALL serum selectively mediates complement dependent cytolysis of lymphoblasts expressing O-AcSAs and thereby possibly confers passive protection. The enhanced anti O-AcSA antibody levels allowed for development of a serodiagnostic assay (BSM-ELISA) specific for ALL. Minimal crossreactivity was observed with other hematological disorders like acute myeloid leukemia (n = 16), chronic myeloid leukemia (n = 6), chronic lymphocytic leukemia (n = 7) and non-Hodgkin's lymphoma (n = 3) as well as normal healthy individuals (n = 28). The BSM-ELISA therefore provides a simple, noninvasive alternative diagnostic approach for ALL and merits clinical consideration.
Pal
S
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Immunobiology, Indian Institute of Chemical Biology, Calcutta, India.
Chatterjee
M
M
Bhattacharya
D K
DK
Bandhyopadhyay
S
S
Mandal
C
C
D000107:Acetylation; D000918:Antibody Specificity; D001323:Autoantibodies / Q000097:blood*; D015153:Blotting, Western; D002051:Burkitt Lymphoma / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D003165:Complement System Proteins / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D004797:Enzyme-Linked Immunosorbent Assay; D004912:Erythrocytes / Q000276:immunology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000276:immunology*; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008297:Male; D009077:Mucins; D019158:N-Acetylneuraminic Acid / Q000276:immunology*
D001323:Autoantibodies; D007074:Immunoglobulin G; D009077:Mucins; D003165:Complement System Proteins; D019158:N-Acetylneuraminic Acid