Selective induction of macrophages in the middle ear.

A method is described for inducing an influx primarily of macrophages into the middle ears of chinchillas using keyhole limpet hemocyanin (KLH, a strong immunogen) and mineral oil (a nonimmunogen) to provide adequate numbers of these cells for study. Although KLH and mineral oil both induced sterile otitis media in which macrophages were the predominant cell type present in the middle ear, the cytological and histological responses of the middle ears to these substances differed. KLH proved to be a much stronger inducer of actively phagocytic macrophages and also produced serous effusions in about 11% of the experimental animals. This experimental model provides an opportunity for the in vitro and in vivo study of the role of macrophages, the predominant cell type associated with human chronic otitis media with effusion, in the defense system of the middle ear.