Expression of the human basophil (BASO) activation marker, CD63, may reflect the extent of degranulation by the AND (anaphylactic degranulation) mechanism. (86.24)

Abstract

Abstract A variety of studies of suggested that expression of two commonly studied BASO activation markers, CD203c and CD63 (a protein associated with the granule membrane), do not always reflect the extent of histamine release (HR). While exploring the role of PKC in the expression of CD63 and CD203c using the PKC inhibitors Ro-31-8220 (RO) or bisindoylmaleimide II (BIS), it was noted that at concentrations (> 3µM) well above the IC50 for inhibition of PKC (100 nM), there was marked enhancement of CD63 expression with only modest enhancement of CD203c expression or HR. Previous studies have shown that BASO either shuttle granule contents out of the cell via small vesicles (piecemeal degranulation, PMD) or by fusion of granules to each other and the plasma membrane (anaphylactic degranulation, AND), these results suggested the hypothesis that high concentrations of RO or BIS induced a switch from PMD to AND. Morphological imaging of stimulated BASO showed a dramatic increase in the appearance of the degranulation sacs associated with AND in the presence of 3 µM RO. While the cytosolic calcium (Ca) response and degranulation sac formation were correlated, 3 µM RO did not alter the Ca response. Therefore, it was proposed that two processes determine the extent of PMD vs. AND, Ca and an unknown RO-sensitive kinase. It is also proposed that CD63 expression occurs predominantly with AND and that the relative amounts of PMD and AND determine the relationship between CD63 expression and HR.