PCA mouse

Passive Cutaneous Anaphylaxis (PCA)

Hooke regularly runs passive cutaneous anaphylaxis (PCA) studies, most often in BALB/c mice. This short in vivo assay is used to test compound effects on antibody-mediated inflammation and anaphylaxis.

Type I hypersensitivity

PCA is a rodent model of type I hypersensitivity, which is an allergic reaction after reexposure to an antigen. Initial exposure to an antigen (an allergen) causes generation of allergen-specific IgE antibodies that bind to FcεRI (high-affinity IgE receptors) on basophils and tissue mast cells. Later exposure to the same allergen results in its (the allergen) binding to IgE on the cell surfaces, cross-linking of FcεRI, cell degranulation, and release of vasoactive and pro-inflammatory mediators (histamine, leukotriene, and prostaglandins).

In humans, common manifestations of type I hypersensitivity reactions include:

PCA model

Mouse ears are injected with anti-dinitrophenol (DNP) IgE monoclonal antibodies, which bind to FcεRI on tissue mast cells. This mimics a primary exposure to the DNP antigen, resulting in sensitization of mast cells and basophils.

24 hours later, DNP-HSA (DNP conjugated to human serum albumen, HSA) is co-administered i.v. with Evans blue dye (a tracer of vascular permeability), resulting in localized degranulation of mast cells, secretion of vasoactive mediators, ear swelling, vascular leakiness and extravasation of Evans blue.

Readouts are change in ear thickness (measured before and after DNP-HSA injection), and Evans blue concentration in ear homogenate.

PCA model diagram

Typical results

The results below are from a representative study performed at Hooke. BALB/c mice were sensitized with anti-DNP IgE antibodies or vehicle (PBS). 23 hours later, and 1 hour before DNP-HSA administration, mice received either vehicle or cyproheptadine (Cypro).

Statistical analysis used ANOVA with Dunnett's comparison to anti-DNP/vehicle control. * p<0.05, ** p<0.01, *** p<0.001

Change in ear thickness (µm +/- SEM)

Ear thickness results

Evans blue

Evans blue results PCA ear image

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Moon TC et al, Front Immunol. 5:569 (2014)
Janeway CA et al, Immunobiology: The Immune System in Health and Disease 5th ed. (2001)