Antigen-presenting cell function of epidermal cells activated by hapten application

Area of Science:

• Immunology
• Dermatology
• Cell Biology

Background:

• Hapten exposure triggers immune responses, including Langerhans cell (LC) migration and T cell activation.
• Antigen-presenting cell (APC) function is crucial for initiating adaptive immunity.
• Epidermal cells (EC) play a role in the immune response to haptens.

Purpose of the Study:

• To investigate the antigen-presenting cell (APC) function of epidermal cells (EC) after hapten application.
• To identify the specific cell types within the epidermis responsible for APC function.
• To understand the molecular mechanisms underlying hapten-induced APC activity in EC.

Main Methods:

• Cell transfer system to assess contact sensitivity (CS) induction.
• Immunomagnetic bead separation to isolate and purify cell populations (Ia+, Thy-1+).
• Monoclonal antibody (mAb) treatment and complement-mediated lysis for cell depletion.
• In vitro culture of EC to assess adherent cell function.
• Flow cytometry to analyze cell surface marker expression (Ia, Thy-1, ICAM-1, B7/BB1).

Main Results:

• Epidermal cells (EC) exhibited antigen-presenting cell (APC) function as early as 6 hours post-hapten application, peaking at 24 hours.
• Depletion of Langerhans cells (LC) did not abolish APC function, while depletion of Thy-1+ cells reduced it.
• Adherent epidermal cells (EC), devoid of LC, demonstrated significant APC capacity.
• Hapten application increased the expression of ICAM-1 and Thy-1 on EC, which were critical for APC function.
• Keratinocytes (KC) were identified as acquiring APC function alongside LC.

Conclusions:

• Hapten application induces both Langerhans cells (LC) and keratinocytes (KC) to become potent antigen-presenting cells (APCs).
• Keratinocytes (KC) contribute to local immune responses by acting as APCs, complementing the function of migrating LC.
• ICAM-1 and Thy-1 expression are key mediators of hapten-induced APC function in epidermal cells (EC).