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Molecular characterization of interleukin 12
F J Podlaski1, V B Nanduri, J D Hulmes
1Department of Protein Biochemistry, Roche Research Center, Hoffmann-La Roche Inc., Nutley, New Jersey 07110-1199.
Archives of Biochemistry and Biophysics
|April 1, 1992
Summary
Interleukin 12 (IL-12) is a cytokine that enhances immune responses by promoting lymphokine-activated killer cells and T-lymphoblast proliferation. Its structure, including disulfide bonds and subunits, is crucial for its bioactivity.
Area of Science:
- Immunology
- Molecular Biology
- Biochemistry
Background:
- Interleukin 12 (IL-12), also known as cytotoxic lymphocyte maturation factor, is a cytokine.
- It is secreted by induced human B lymphoblastoid (NC-37) cells.
Purpose of the Study:
- To purify and characterize Interleukin 12 (IL-12).
- To investigate the synergistic effects of IL-12 with Interleukin 2 (IL-2) on immune cells.
- To elucidate the structural components and their role in IL-12 bioactivity.
Main Methods:
- Purification of IL-12 to homogeneity.
- Assays for lymphokine-activated killer cell induction and lymphoblast proliferation.
- Amino acid sequencing, deglycosylation, and site-specific chemical modification.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting.
Main Results:
- Purified IL-12 synergizes with IL-2 to induce lymphokine-activated killer cells.
- IL-12 alone stimulates lymphoblast proliferation and shows additive effects with IL-2.
- IL-12 is a heterodimer of 40- and 35-kDa subunits, with glycosylation on both.
- Intact disulfide bonds are essential for IL-12 bioactivity.
- The 40-kDa subunit is abundant but lacks activity alone, suggesting a role in receptor interaction.
Conclusions:
- IL-12 is a potent immune-stimulating cytokine with a complex heterodimeric structure.
- Specific structural features, including disulfide bonds and subunits, are critical for its function.
- The 40-kDa subunit may play a direct role in IL-12 receptor binding.