IN-VIVO INDUCTION OF MACROPHAGE IA-ANTIGEN (MHC CLASS-II) EXPRESSION BY BIOMEDICAL POLYMERS IN THE CAGE IMPLANT SYSTEM

Examination of the cellular components in the inflammatory exudate, wh ich infiltrates subcutaneous cages, can be used to monitor the progres s of an inflammatory response to an implanted material. Of particular interest is the study monocyte/macrophage infiltration into the implan ted cages containing biomaterials, as macrophages may initiate a wide spectrum of responses upon interaction with a foreign material. In thi s study, the authors propose a technique using subcutaneous tissue cag es in conjunction with cytofluorimetric analysis of exudate leukocytes to evaluate the monocyte/macrophage cell activation in response to di fferent materials. The studies reported here used several materials (t hermoplastic and elastomeric polymers) as the challenging agent, to de monstrate whether polymers, chemically different from each other, coul d differentially activate macrophages to carry out their proinflammato ry role more effectively. The materials tested included: poly(etherure thane ureas) (PEUU A'), poly(etherurethane ureas) with a surface activ e additive, Methacrol(R), (PEUU C'), polymethylsiloxane (PDMS), polyet herimide, (PEI), and polyetheretherketone, (PEEK). For all the tested materials, the maximum numbers of exudate cells and of Ia-positive mac rophages were found on day 7, although the entity of the cell increase was associated with the material used for the implant. Similarly, the percentage of Ia-positive macrophages varied according to the specifi c polymer present in the cages after 7 days. By day 14 the percentage of Ia-positive macrophages decreased with individual exudates showing 19-32% Ia-positive cells depending on the different type of material. Only in the case of PDMS did the percentage of Ia-positive macrophages remain the same as compared with control empty cage macrophages. (C) 1994 John Wiley and Sons, Inc.