Acquisition and alteration of adhesion molecules during cultured human mast cell differentiation

Background: Mature human mast cells express several types of adhesion molecules on their surface. Interactions between extracellular matrix (ECM) and adhesion molecules may be important for the migration and localization of mast cells and their precursors in tissues. Little is known about the regulation of adhesion molecules on mast cells during their differentiation. Objectives: To clarify the evolution of adhesion phenotype and function, we examined the expression of adhesion molecules during cultured human mast cell (CHMC) differentiation and tested adhesion of mature CHMCs to various ECM proteins. Methods: CHMCs were obtained by culturing human cord blood-derived CD34⁺ cells in the presence of stem cell factor and IL-6. Indirect immunofluorescence and flow cytometry was used to study cell surface expression of adhesion molecules and other markers. Mature CHMCs were tested for adhesion molecule function with immobilized matrix proteins. Results: At 1 week of culture, cells expressed CD11a, CD18, CD29, CD49d, and CD49e. At 14 weeks of culture, more mature CHMCs expressed CD11b, CD11c, CD29, CD49b, CD49c, CD49d, CD49e, CD51, CD61, and CD54 and weakly expressed CD18 and CD11a. CD11c, CD51, and CD61 appeared de novo by 4 weeks of culture, whereas CD49b and CD49c appeared by 8 weeks. CD29 decreased at 4 weeks but returned to the identical levels of 1-week-old cells by 8 weeks. Compared with levels at week 1, the levels of CD11a, CD18, CD49d, and CD49e at 4 weeks and beyond decreased during culture. Expression of CD49a, CD49f, and αd integrin was never detectable during CHMC differentiation. Fourteen-week-old CHMCs significantly adhered to the leucine-aspartic acid-valine - containing connecting segment 1 fragment of fibronectin, the 120-kd argine-glycine-aspartic acid - containing fragment of fibronectin, vitronectin, and laminin through specific integrins. Conclusion: Expression of integrins and CD54 is differentially regulated during CHMC differentiation, and mature CHMCs can adhere to many ECM proteins. These changes may facilitate emigration from the bone marrow into the circulation and ultimately contribute to the tissue homing and localization pattern seen with mature mast cells.