Studies have been extended on the effects of laminin on phagocytosis. Using culture-derived human macrophages that are exposed to laminin we showed enhanced phagocytosis of EAC4b, EAC3bi and EA(IgG). The effect required interaction of laminin with the phagocytic cell and not opsonized particle. Direct comparison of the phagocytic ability of macrophages adherent to laminin and fibronectin coated glass slides showed that fibronectin had a greater effect on enhancing phagocytosis. This work shows the important stimulus of extracellular matrix proteins that activates macrophages normally present in the extracellular compartment and to the phagocytic cells that emigrate from the bloodstream to areas of inflammation. New studies examined the interaction of C1q and laminin. Preliminary data suggests that laminin binds to the collagen-like tail of C1q via a short arm of laminin. The binding of laminin to C1q was stronger than the binding of C1q to fibronectin. A complex formed by laminin, C1q and aggregated IgG was dependent on the proportional amount of C1q bound to the aggregated IgG. Since laminin is found only in basement membranes, the interaction between laminin and C1q could be involved in the depostion and retention of immune complexes in these structures.
