The BasoStep kit from Immunostep
Products are for professional/laboratory use only
The BasoStep kit – A means of demonstrating antigen specific IgE hypersensitivity.
Basophil Activation
Clinical relevance – IgE mediated hypersensitivity
In susceptible people, IgE is produced by B cells in response to specific antigens such as foods, pollens, latex, and drugs. This antigen-specific (or allergen-specific) IgE circulates in the serum and binds to high-affinity IgE receptors on immune effector cells such as mast cells located throughout the body.
Upon subsequent exposure to the same allergen, IgE receptors cross-link and initiate downstream signalling events that trigger mast cell degranulation and an immediate allergic response—hence the term immediate hypersensitivity. Basophils are among the least abundant populations of circulating leukocytes, but by virtue of their sensitization with allergen-specific IgE, they represent a significant effector population in allergic pathogenesis.
Basophils are known to be an early and abundant source of Th2 cytokines and other mediators of Th2 inflammation. There is also growing recognition of their capacity to modulate adaptive immunity.
A means of demonstrating allergen sensitivity
The kit is based on the method described by Sainte-Laudy et al. 1994 where basophil activation by allergens is detected by flow cytometry measured by the increase of CD63 (gp53) at the cellular surface.
BasoStep allows the quantitative 
determination of human basophils degranulation. The test includes the chemotactic peptide N-formyl-Met-Leu-Phe (fMLP) as positive control and a cocktail of antibodies for detection and determination of degranulated basophils activation. Therefore, BasoStep assay is based on in-vitro stimulation of basophils using fMLP as positive control and subsequent flow cytometry analysis of membrane expression of CD63 on basophils after degranulation. Using defined allergens, this test provides information concerning the releasability of IgE-bearing basophils.
When IgE-receptors on basophils are cross-linked by an allergen the cells undergo degranulation through cytoplasmatic granules containing the CD63 transmembrane protein fuse with the plasma membrane and release inflammatory mediators. Therefore, the CD63 antigen is exposed as a marker of basophil activation.
The histogram is a representation of a lysate normal whole blood sample gated on CD123+/CD203c+/HLA-DR-. Control Negative are represented by the yellow histogram and Positive Control by red histogram. Cells were analysed on a FACSAria II (Becton Dickinson, San Jose, CA) flow cytometer, using BD FACSDiva software.
