Effect of low-density lipoprotein (LDL) antigen source on an enzyme-linked immunosorbent assay for autoantibodies against oxidized LDL.
We examined the effect of antigen source on an enzyme-linked immunosorbent assay (ELISA) for autoantibodies against oxidized low-density lipoprotein (LDL). Serum samples from 20 subjects with systemic lupus erythematosus (SLE) and from 20 controls were assayed for immunoglobulin G (IgG) and immunoglobulin M (IgM) autoantibodies against oxidized LDL, using either a pooled or individual (n = 3) LDL preparation as antigen. For IgG autoantibodies against oxidized LDL there was a relationship (r approximately 0.5, P < 0.01) between data obtained using individual versus pooled antigen preparations. Bias plots demonstrated consistent inverse, concentration-dependent relationships (r approximately -0.6, P < 0.001). The difference in IgG autoantibodies against oxidized LDL levels between SLE patients and controls was underestimated (39-58%) when assays used individual rather than pooled LDL antigen. For IgM autoantibodies against oxidized LDL the direct relationships were stronger (r approximately 0.8, P < 0.001) and the concentration-dependent relationships weaker (r approximately -0.3, significance variable) than for IgG autoantibodies against oxidized LDL. Variations between LDL preparations suggested that a pooled antigen would give a more stable assay. Thus, LDL antigen source is important in assays for both IgG and IgM autoantibodies against oxidized LDL.
Craig
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WY
Foundation for Blood Research, Scarborough, Maine 04070-0190, USA. wcraig@fbr.org
Raytcheva
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SE
Poulin
S E
SE
Ritchie
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RF
D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000032:analysis*; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D008077:Lipoproteins, LDL / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results
D001323:Autoantibodies; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D008077:Lipoproteins, LDL; C099252:oxidized low density lipoprotein