Phenotypic and functional characterization of in vitro cultured human mast cells.

BACKGROUND

Mast cell progenitor cells, derived from CD34 hematopoietic stem cells, enter the circulation and subsequently mucosal or connective tissues where they mature to mast cells. Upon activation, mast cells increase the expression of activation markers, e.g. CD63, and release histamine amongst other mediators. Traditionally, release of these mediators is quantified using assays measuring their extracellular concentration in the supernatant of stimulated cells.

METHODS

Human mast cells (HuMC) were cultured from peripheral blood, phenotypically characterized, passively sensitized with allogenic IgE antibodies and finally stimulated by anti-IgE that crosslinks IgE/FcεRI complexes. Alterations in the number of cells positive for CD63 and release of histamine were quantified simultaneously by flow cytometry.

RESULTS

In culture, two distinct CD45 cell populations were identified: CD117 CD203c and CD117 CD203c cells. Both populations showed positivity for FcεRI, tryptase and chymase, and contained histamine. Activation resulted in a significant increase of cells positive for CD63 up to 21% (range: 11-39) for CD117 CD203c cells (P = 0.005), and 27% (18-55) CD63 for CD117 CD203c cells (P = 0.02). Baseline histamine content was higher for CD117 CD203c cells than for CD117 CD203c cells, respectively 994 (695-6815) Molecules of Equivalent Specific Fluorochrome V500 per cell (MESF-V500/cell) and 797 (629-4978) MESF-V500/cell (P = 0.02). After activation, CD117 CD203c cells showed significant histamine release of 578 (366-1521) MESF-V500/cell, whilst CD117 CD203c cells resulted in 310 (217-366) MESF-V500/cell histamine release.

CONCLUSION

This study discloses that culturing HuMC from CD34 progenitors yields 2 phenotypically distinct cell populations that display a greatly similar response upon cross-linking of IgE/FcεRI complexes. © 2016 International Clinical Cytometry Society.