Bovine spleen, a convenient source for purifying a type I interferon receptor

Area of Science:

• Biochemistry
• Immunology
• Veterinary Science

Background:

• Interferons (IFNs) are crucial cytokines in immune responses.
• Understanding IFN receptor distribution is key to their therapeutic applications.
• Bovine spleen as a potential source of IFN receptors was unexplored.

Purpose of the Study:

• To investigate the presence and characteristics of human interferon-alpha 2 (HuIFN-alpha 2) receptors in bovine spleen.
• To quantify the binding affinity and receptor density on bovine spleen membranes.
• To identify and characterize the molecular nature of the IFN-receptor complex.

Main Methods:

• Preparation of bovine spleen membranes via homogenization and differential centrifugation.
• Analysis of radioiodinated HuIFN-alpha 2 binding using tissue membrane assays.
• Chemical cross-linking of the IFN-receptor complex with EGS, followed by SDS-PAGE and autoradiography.
• Purification of cross-linked products and enzymatic digestion with Endoglycosidase H and PNGase F.

Main Results:

• Specific binding of HuIFN-alpha 2 to bovine spleen membranes was confirmed.
• High affinity constant (Ka = 3.1 x 10^10 M-1) and receptor content (8.4 fmoles/mg) were determined.
• A 137-kD cross-linked complex was identified, inhibited by unlabeled HuIFN-alpha 2.
• PNGase F digestion shifted the complex to 105 kD, indicating N-linked glycosylation.

Conclusions:

• Bovine spleen possesses specific receptors for human interferon-alpha 2.
• The identified 137-kD complex represents the HuIFN-alpha 2 receptor, with a core protein of approximately 105 kD.
• These findings contribute to understanding IFN receptor biology in non-primate species.