BACKGROUND: Mast cells and basophils are effector cells of allergic reactions and display a number of activation-linked cell surface antigens. Of these antigens, however, only a few are functionally relevant and specifically expressed in these cells.
OBJECTIVE: To identify mast cell- and basophil-specific surface molecules and to study their cellular distribution and regulation during cytokine-induced and IgE-dependent activation.
METHODS: Multi-color flow cytometry was performed to recognize surface antigens and to determine changes in antigen expression upon activation.
RESULTS: We identified Siglec-6 (CD327) as a differentially regulated surface antigen on human mast cells and basophils. In the bone marrow, Siglec-6 was expressed abundantly on mast cells in patients with mastocytosis and in reactive states, but was not detected on other myeloid cells, with the exception of basophils and monocytes. In healthy individuals, allergic patients, and patients with chronic myeloid leukemia (CML), Siglec-6 was identified on CD203c+ blood basophils, a subset of CD19+ B lymphocytes and few CD14+ monocytes, but not on other blood leukocytes. CML basophils expressed higher levels of Siglec-6 than normal basophils. Interleukin-3 (IL-3) promoted Siglec-6 expression on normal and CML basophils, and stem cell factor (SCF) increased the expression of Siglec-6 on tissue mast cells. Unexpectedly, IgE-dependent activation resulted in downregulation of Siglec-6 in IL-3-primed basophils whereas in mast cells, IgE-dependent activation augmented SCF-induced upregulation of Siglec-6.
CONCLUSIONS: Siglec-6 is a dynamically regulated marker of mast cells and basophils. Activated mast cells and basophils exhibit unique ´Siglec-6-responses´, including cytokine-dependent upregulation and unique differential, cell-specific responses to IgE-receptor cross-linking.
- mast cells
ASJC Scopus subject areas
- Immunology and Allergy