Lysis of mouse macrophages, fibroblasts, and epidermal cells by epidermal alloantigen-specific cytotoxic T lymphocytes: Effect of culture and inflammatory agents on Epa-1 expression

The expression of Epa-1, a tissue-restricted non-major histocompatibility complex (MHC) alloantigen, on CBA epidermal cells (EC), fibroblasts (FB), and macrophages (Mφ) was investigated using bulk-cultured and clonally-derived anti-Epa-1 cytotoxic T lymphocytes (CTL). Epa-1 was readily detected on freshly trypsinized and 24-hr-cultured EC, and on skin FB cultured for 1–3 weeks. In contrast, fresh peritoneal (PE) Mφ were specifically resistant to Epa-1 CTL but became susceptible after 12–24 hr in culture. Epa-1 expression by PE Mφ also could be induced in vivo by Mφ-activating agents such as concanavalin A or Bacillus Calmette-Guérin (BCG), but not by the sterile inflammatory agents peptone broth or thioglycolate, suggesting a correlation between Epa-1 phenotype and Mφ activation. From this and from parallel studies of spleen cell Mφ it is concluded that Epa-1 may be a strain-specific marker for activated Mφ in the mouse, as well as an inducible histocompatibility antigen in vivo.