Epidermal growth factor and transforming growth factor-alpha decrease gamma interferon receptors and induction of...

Area of Science:

• Immunodermatology
• Cellular immunology
• Cytokine signaling

Background:

• Epidermal keratinocytes and T lymphocytes interact via cytokines like gamma interferon (IFN-gamma).
• Keratinocyte growth is influenced by mitogens such as transforming growth factor-alpha (TGF-alpha) and epidermal growth factor (EGF).

Purpose of the Study:

• To investigate how keratinocyte mitogens (TGF-alpha, EGF, SM-C) affect IFN-gamma receptor binding on cultured human skin keratinocytes.
• To determine the immunobiological consequences of altered IFN-gamma receptor expression.

Main Methods:

• Cultured human keratinocytes were treated with mitogens (TGF-alpha, EGF, SM-C) or grown in mitogen-free medium.
• 32P-labeled IFN-gamma ligand binding assays were performed to quantify high-affinity receptors.
• Expression of HLA-DR and ICAM-1 was assessed following IFN-gamma stimulation.

Main Results:

• Quiescent keratinocytes (no mitogens) had 2.4 times more high-affinity IFN-gamma receptors than actively growing cells treated with TGF-alpha or EGF.
• TGF-alpha/EGF-induced reduction in IFN-gamma receptors was mitogen-specific and time-dependent (24-48 hours).
• Somatomedin-C (SM-C) did not affect IFN-gamma receptor levels despite stimulating keratinocyte growth.
• Quiescent keratinocytes showed increased IFN-gamma-induced HLA-DR and ICAM-1 expression compared to actively growing cells.

Conclusions:

• Actively proliferating keratinocytes, stimulated by TGF-alpha/EGF but not SM-C, downregulate high-affinity IFN-gamma receptors.
• This downregulation alters keratinocyte responsiveness to IFN-gamma, impacting immune cell interactions.
• Keratinocyte proliferation state significantly modulates its immune signaling capacity.