MHC class II antigen expression is increased in different forms of urticaria

Area of Science:

• Immunology
• Dermatology
• Cell Biology

Background:

• Urticarial reactions involve complex inflammatory and immunological processes.
• Understanding the role of specific molecules like MHC class II is crucial for elucidating urticarial pathomechanisms.

Purpose of the Study:

• To analyze the distribution and sequential expression of major histocompatibility complex class II (MHC class II) molecules in various whealing reactions.
• To compare MHC class II expression in early versus longer-lasting urticarial lesions and lesional versus uninvolved skin.

Main Methods:

• Immunohistochemical techniques using monoclonal antibodies to detect HLA-DR, HLA-DP, and HLA-DQ.
• Examination of tissue sections from different types of urticarial reactions, including sequential biopsies in cold urticaria.
• Comparison of expression on resident and infiltrating cells across various skin compartments.

Main Results:

• No increased MHC class II expression was found in early allergen prick test wheals.
• Sequential biopsies in cold urticaria showed MHC class II upregulation within 30 minutes of elicitation.
• Upregulation of MHC class II molecules (HLA-DR, HLA-DP, HLA-DQ) was pronounced in longer-lasting urticarial lesions (acute, chronic recurrent, delayed pressure) on various cell types and in nonlesional skin.

Conclusions:

• Longer-lasting urticarial wheals are associated with increased MHC class II expression on both resident and infiltrating cells.
• These findings suggest a significant involvement of MHC class II molecules in the pathogenesis of these urticarial lesions.
• MHC class II upregulation may serve as a marker for specific types of chronic urticaria.