Complement receptors of rat macrophages.

Some species, including rabbits, guinea pigs, and humans, have complement receptors on resident alveolar macrophages, whereas Swiss mice lack detectable receptors on these macrophages. Using complement-coated sheep erythrocytes or bacteria, we were unable to detect complement receptors (CR1, CR2, or CR3) on resident alveolar macrophages of male Sprague-Dawley rats. Nonelicited peritoneal macrophages from Sprague-Dawley rats had CR1 and CR3 receptors and were able to bind bacteria opsonized with complement. Resident alveolar macrophages of Long-Evans and Fisher rats lacked detectable complement receptors, but CR1 and CR3 receptors were detected on the alveolar macrophages of Lewis-Wistar rats. The reason for the lack of complement receptors on murine macrophages is not known, but studies of this phenomenon may prove useful in elucidating the role of macrophage complement receptors in the pulmonary inflammatory response.