STAPHYLOCOCCUS-EPIDERMIDIS GRAFT INFECTION IS ASSOCIATED WITH LOCALLYSUPPRESSED MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II AND ELEVATED MAC-1 EXPRESSION

Objective: To determine the local cellular immune response in a series of human patients with Staphylococcus epidermidis prosthetic graft in fection and to use a murine model to investigate the response in polyt ef (PTFE) and in a nonslime-producing S epidermidis variant. Methods: Externally supported Dacron and PTFE grafts, either sterile or coloniz ed with slime (RP-62A)- or nonslime (RP-62NA)-producing S epidermidis (10(7) colony forming units/cm(2)) were implanted in a dorsal subcutan eous pocket of Swiss Webster mice (Taconic, Germantown, NY). The graft s were harvested at 7, 10, 14, and 28 days with local bacterial and le ukocyte counts obtained. Perigraft and blood monocyte major histocompa tibility complex class II (MHC-II) (immune antigen) and membrane attac k complex type 1 (MAC-1) (glycoprotein) expression were analyzed by fl ow cytometry in the murine model and in 3 patients representing 4 Dacr on graft infections. Results: The human infected Dacron perigraft mono cytes revealed a suppressed MHC-II and elevated MAC-1 expression, and early correlation with the murine model was seen. No notable perigraft monocyte MHC-II suppression occurred in the infected PTFE graft. The reciprocal relationship in Dacron between monocyte MAC-1 and MHC-II ex pression was exaggerated with the lack of slime production. Bacterial clearance was variable. Supranormal expression was observed at I month in sterile Dacron but not in PTFE grafts. Conclusions: Staphylococcus epidermidis infection is associated with local cellular immune suppre ssion in Dacron but not PTFE grafts. Slime-producing S epidermidis ind uced a lesser cytotoxic-phagocytic response than the nonslime variant. The reduced immunologic response to slime-producing S epidermidis may explain, in part, its indolent nature and resistance to eradication.