Role of adherence vs. spreading in the induction of membrane-associated interleukin-1 on mouse peritoneal macrophages.

Adherence of peritoneal exudate cells (PEC) to plastic has been shown to activate several PEC functions, such as tumor cell lysis and membrane-associated interleukin-1 (mIL-1) expression. Several studies have demonstrated that leukocyte adherence is dependent on divalent cations. In this study, ethylenediaminetetraacetic acid (EDTA), a known chelator of divalent cations, was used to evaluate the role of cell attachment vs. spreading in adherence-induced mIL-1 activity on resident C57BL/6 mouse PEC. Significant inhibition of PEC spreading on plastic and mIL-1 expression was noted when PEC were cultured in the presence of 10 mM EDTA. However, PEC remained adherent in the presence of EDTA and were able to express mIL-1 activity in response to a soluble stimulus lipopolysaccharide (LPS) 1 microgram/ml. These results suggest that the divalent cation-dependent spreading of PEC on plastic initiates or enhances the expression of mIL-1 activity. Additionally, adhesion and LPS stimulate mIL-1 expression by independent mechanisms.