This study investigates the immune response to hapten exposure in a mouse model. It details the process from antigen application to the activation of T cells and the resulting 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.
To begin, anesthetize the mouse with an intraperitoneal injection of an anesthetic cocktail, and confirm adequate sedation with a toe pinch test. Next, apply hair removal cream to the dorsal surface of both ears. Wipe it off within a minute and wash the skin with water.
Measure the thickness of the ear where the applications were made using a micrometer. Later, return the mouse in its own cage after it is recovered from the anesthesia, and allow the mouse to rest for at least three days before further testing.
After three days, re-anesthetize the mouse and measure the ear thickness again to make sure it is not irritated. Then, apply 12.5 microliters of 1.25% oxazolone onto each side of the right ear, and apply 12.5 microliters of the acetone-olive oil vehicle solution onto each side of the left ear.
As always, observe the mouse recover from the anesthesia. 24 hours later, measure the thickness of the ear again under anesthesia, to ensure the oxazolone-induced skin inflammation has occurred.
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