MODULATION OF β‐GALACTOSIDASE ACTIVITY IN PERITONEAL MACROPHAGES FROM C57B1 MICE AFTER EXPOSURE TO PROPRIONIBACTERIUM ACNES

Peritoneal macrophages (PMo) from untreated C57B1 mice contain high levels of β-galactosidase (β-gal) and these PMo are heterogeneous in their expression of this enzyme. Intraperitoneal (i.p.) injection of saline caused a transient depression in the level of enzyme activiy in the PMo whereas i.p. injection of Proprionibactcrium acnes (P. acnes) gave rise to a marked decrease of β-gal activity in these cells. This reduction in enzymatic activity persisted for as long as the PMo were activated for cytotoxicity towards the L929 tumor cell line, up to 35 days after injection, β-gal activity was present in the lavage fluid from day 2–21 after injection of P. acnes but none was detected in the lavage fluid after injection of saline. It is proposed that the enzymatic activity in the lavage fluid is derived from monocytes which migrate from the blood into the peritoneal cavity. There was an influx of granulocytes in the P. acnes group which persisted up to 35 days after injection. In contrast none were observed in the saline group after 2 days. PMo harvested after 1–35 days were large, highly vacuolized and many contained bacteria; these PMo had the typical morphology of activated cells. It is suggested that the processing of P. acnes by granulocytes may play a role in the activation of macrophages in the early inflammatory response, with concurrent loss in β-gal activity. However, in the later stages, interferon-γ and other induced lymphokines may be instrumental in causing a decrease in β-gal activity.