A Technique to Assess the Immune Response against an Antigen by Inducing Skin Inflammation

Take an anesthetized mouse with depilated ears, and apply the test antigen — a hapten mixed in a suitable vehicle solution — on the exposed skin. The vehicle solution facilitates hapten penetration through the outermost epidermis layer to reach the underlying dermis.

Hapten binds to skin proteins, forming an immunogen recognized by antigen-presenting cells or APCs. Upon engulfment, APCs process and display the immunogen on their surface.

APCs migrate to lymph nodes, presenting the immunogen to naïve T cells and activating them. Activated cells differentiate into primed memory T cells — a subset of which migrate to the skin.

Upon hapten re-exposure, APCs present the immunogen to the primed T cells, inducing pro-inflammatory cytokine release.

Cytokines trigger keratinocytes and mast cells to release chemokines, which bind to circulating neutrophils, facilitating their extravasation. The extravasated neutrophils reach the inflammation site.

Cytokines activate neutrophils to produce proteolytic enzymes and reactive oxygen species — causing tissue damage and amplifying the inflammation.