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IL-12 is a heparin-binding cytokine
M Hasan1, S Najjam, M Y Gordon
1Division of Biochemistry, Royal Holloway University of London, Egham, Surrey, United Kingdom.
Journal of Immunology (Baltimore, Md. : 1950)
|January 23, 1999
Summary
Interleukin-12 (IL-12) is identified as a heparin-binding cytokine. This property suggests IL-12 may remain localized near its secretion site, facilitating a paracrine signaling role.
Area of Science:
- Immunology
- Biochemistry
- Cytokine Biology
Background:
- Interleukin-12 (IL-12) is a key cytokine in T-helper 1 (Th1) immune responses.
- Understanding cytokine-heparin interactions is crucial for elucidating their biological functions and localization.
Purpose of the Study:
- To investigate whether Interleukin-12 (IL-12) binds to heparin.
- To characterize the specificity and affinity of IL-12 binding to heparin.
- To determine which subunit of IL-12 mediates heparin binding.
Main Methods:
- Enzyme-Linked Immunosorbent Assay (ELISA) was employed to assess binding.
- Competition assays using soluble heparin and various glycosaminoglycans were performed.
- Analysis of binding inhibition by heparin fragments of different sizes and origins was conducted.
Main Results:
- Recombinant human IL-12 (rhIL-12) demonstrated strong binding to immobilized heparin.
- Binding was specific for heparin, with weak or no competition from chondroitin sulfates.
- The p40 subunit of IL-12 appears to contain the primary heparin-binding site.
- IL-12 exhibits high affinity for heparin, comparable to FGF-2.
Conclusions:
- IL-12 is confirmed as a heparin-binding cytokine, similar to IFN-gamma and IL-2.
- Heparin binding likely retains IL-12 near its secretion site, promoting a paracrine function.
- This interaction may influence the local immune response mediated by IL-12.