title: Liposomes expressing IL 1 biological activity.
abstract: We determined the activity of IL 1, obtained from various human monocyte subcellular compartments, when associated with liposomes. Soluble IL 1, bound to the outer surface of lyophilized liposomes, stimulated responsive target cells. However, this activity was not preserved when soluble IL 1 was incorporated into the inner chambers of classical liposomes. In contrast, monocyte plasma membranes that exhibited IL 1 activity had the same level of activity when presented on lyophilized liposomes and when incorporated inside the classical liposomes. However, monocyte plasma membranes bound to the outer surface of the liposomes exhibited greater activity than the monocyte membrane IL 1 itself in its soluble form. This suggests that membrane IL 1 is an integral membrane protein, readily integrated into the lipid bilayers. Like soluble IL 1, the expression of IL 1 activity present in the cytosol of activated monocytes was decreased by incorporation into liposomes, but was high and active when presented on lyophilized liposomes. The best artificial cell reconstitution was obtained with lyophilized liposomes in association with monocyte cytosol and plasma membranes. When an unactivated monocyte compartment was mixed with one from an activated monocyte, the signal was equal to that of the activated cell compartment alone. The IL 1 activity of activated cell fractions associated with lyophilized liposomes was determined, and an increase of IL 1 activity for both plasma membranes and cytosol was observed, whereas a decrease of the signal was obtained for the lysosomal compartment. Endoplasmic reticulum showed no IL 1 activity, even after trypsin treatment. The highest activity after trypsin treatment was recovered in the cytosol associated with lyophilized liposomes, suggesting that molecules obtained after this treatment were able to bind tightly to the lipid bilayers.
mesh_terms: D002451:Cell Compartmentation; D002462:Cell Membrane / Q000032:analysis; D002474:Cell-Free System; D003600:Cytosol / Q000032:analysis; D006801:Humans; D007375:Interleukin-1 / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D008051:Lipid Bilayers; D008081:Liposomes; D008213:Lymphocyte Activation / Q000187:drug effects; D008247:Lysosomes / Q000032:analysis; D008565:Membrane Proteins / Q000302:isolation & purification; D009000:Monocytes / Q000032:analysis; D012995:Solubility
chemical_list: D007375:Interleukin-1; D008051:Lipid Bilayers; D008081:Liposomes; D008565:Membrane Proteins