IgG and IgA with potential microbial-binding activity are expressed by normal human skin epidermal cells

Area of Science:

• Immunology
• Dermatology
• Cell Biology

Background:

• The skin's innate immunity relies on mechanical barriers and antimicrobial peptides.
• Epidermal antibody secretion has not been previously reported.
• Immunoglobulin G (IgG) and Immunoglobulin A (IgA) are crucial for adaptive immunity, typically produced by B cells.

Purpose of the Study:

• To investigate the expression and function of IgG and IgA in normal human epidermal cells.
• To determine if epidermal cells can produce antibodies independently of B cells.
• To explore the potential role of epidermal antibodies in skin innate immunity.

Main Methods:

• Analysis of immunoglobulin expression in normal human epidermal cells and HaCaT keratinocytes.
• Sequencing of VDJ rearrangements in epidermal IgG and IgA.
• Immunohistochemical localization of IgG and IgA within epidermal layers.
• Assessment of antibody binding activity against Staphylococcus aureus.

Main Results:

• Functional IgG and IgA were detected in normal human epidermal cells and HaCaT cells.
• Epidermal IgG and IgA exhibited unique, conservative VDJ rearrangements distinct from B cell-derived antibodies.
• IgG was localized in prickle cells, while IgA was found in basal cells.
• Both epidermal IgG and IgA demonstrated pathogen-binding activity against Staphylococcus aureus, with differing profiles.

Conclusions:

• Normal human epidermal cells spontaneously express functional IgG and IgA.
• Epidermal antibodies possess unique VDJ rearrangements, suggesting an independent production pathway.
• These findings indicate a novel role for epidermal IgG and IgA in contributing to the skin's innate immune defense against pathogens.