Background
Human basophils are granulocytes with the capacity to play important roles in allergy for example by releasing histamine when activated by cross-linking of their high affinity IgE receptors (Fc¿RI). However, not all individuals have basophils responding with a histamine release after such activation and are therefore called nonreleasers. Intracellularly these basophils differ from responding cells by having a low level of the tyrosine kinase Syk, but studies of their surface profile are lacking.
We have investigated the expression of Fc¿RI, HLA-DR, CD16, CD63, CD69, CD117, CD123, CD124, CD203c, C3aR, C5aR CCR3, FPR1, ST2, CRTH2 on anti-IgE respondsive and nonreleasing basophils by flow cytometry, thereby generating a surface profile of the two phenotypes.

Methods
Fresh buffy coat blood (< 6h) were screened for anti-IgE mediated histamine release and nonreleases were defined as having a maximum release < 12.7%.
Periphereal blood mononuclear cells were purified by density centrifugation and using flow cytometry, basophils, defined as FceRIa+CD3-CD14-CD19-CD56-,were analysed for surface expression of relevant markers. All samples were compensated and analysed in logicle display. All gates were set on FMO (fluorescence minus one) controls and results are given in geoMFI normalised to FMO control. Releaser and nonreleasers were compared using unpaired t test with Welch’s correction.

Results
Twelve donors were included, three of which were nonreleasers and characterized in regard to surface expression of Fc¿RI, HLA-DR, CD16, CD63, CD69, CD117, CD123, CD124, CD203c, C3aR, C5aR CCR3, FPR1, ST2 and CRTH2. No significant difference was observed between normal and nonresponding basophils with any of the investigated receptors, even though a trend was found with CD203c indicating a lower expression on nonreleasers (p = 0.0609).

Conclusion
Surface profiling using 15 different receptors, illustrated no significant difference between normal and nonreleasing basophils.