Characterization and detection of naturally occurring antibodies against IL-1 alpha and IL-1 beta in normal human plasma.
During the development and testing of a radioreceptor assay (RRA) for human IL-1, we have detected and identified the presence of auto-antibodies to IL-1 in normal human plasma (NHP). The RRA is based on the competition between human 125I-labeled rIL-1 alpha and standard or unknown quantities of IL-1 alpha or IL-1 beta for binding to a limited amounts of IL-1 receptor (IL-1R) isolated from the EL4 mouse thymoma cell line. NHP from 20 out of 100 unselected blood donors were found to completely inhibit the binding of 125I-labeled IL-1 alpha to its receptor, suggesting the presence in these NHP samples of either abnormal amounts of IL-1 or of a factor binding to the 125I-labeled IL-1 alpha. Special care was taken to ascertain that the inhibitory factors were antibodies and not soluble IL-1 receptor antagonist. When plasma samples with inhibiting activity were incubated with labeled IL-1 alpha and chromatographed on a Sephadex G200 column, they were found to contain 125I-labeled complexes with an apparent molecular weight of 150-200kD. The IL-1 binding factor could be eliminated from plasma by incubation with protein A-Sepharose, suggesting that it consisted in IgG antibodies directed against IL-1. Furthermore, the antibody nature of the inhibiting factor was confirmed by its binding to purified rIL-1 coupled to Sepharose. Screening of 200 NHP samples by incubation with 100 pg of 125I-labeled IL-1 followed by precipitation with 12% of polyethylene glycol (PEG) confirmed that about 25% of NHP contain detectable IgG antibodies to IL-1 alpha, while only 2% of NHP contain antibodies to IL-1 beta. No correlation between the presence of these anti-IL-1 antibodies and any particular major histocompatibility complex or any pathological conditions was detected. We suggest that all serum samples assayed for IL-1 alpha or IL-1 beta content should be pretested with the PEG precipitation assay described here.
Gallay
P
P
Institute of Biochemistry, University of Lausanne, Epalinges, Switzerland.
Mach
J P
JP
Carrel
S
S
D000906:Antibodies / Q000097:blood*; D002850:Chromatography, Gel; D003429:Cross Reactions; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D007375:Interleukin-1 / Q000276:immunology* / Q000378:metabolism; D011869:Radioligand Assay; D011971:Receptors, Immunologic / Q000378:metabolism; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins / Q000276:immunology; D012016:Reference Values; D013379:Substrate Specificity
D000906:Antibodies; D007074:Immunoglobulin G; D007375:Interleukin-1; D011971:Receptors, Immunologic; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins