Differentiation significantly increases the number of tTG molecules expressed on the surface of THP-1 monocytic cells and human peripheral blood monocytes.

THP-1-cells (A) or peripheral blood monocytes (B) were kept in suspension without treatment or plated on Fn and stimulated with 150 ng/mL TPA (A) or 5 ng/mL M-CSF (B) for indicated time periods. Cells (2 × 10⁵) were incubated in suspension for 45 minutes at 4°C with 10 μg/mL ¹²⁵I-labeled mAb 4G3 against tTG. The amounts of ¹²⁵I-labeled mAb 4G3 bound to cell surfaces were determined in a gamma counter. The numbers of cell surface tTG molecules on THP-1 cells and human monocytes were determined by subtracting nonspecific binding in the presence of excess unlabeled mAb 4G3. Shown are the means of 3 separate experiments performed in duplicate.