Bovine serum albumin (BSA) in complete Freund's adjuvant (CFA) was injected into the knee joints of previously BSA-sensitized guinea pigs and rabbits. The primary immune reaction to BSA prevented secondary immune response to Trichinella larvae infection. We were unable to produce either eosinophilia in the peripheral blood or antibodies against Trichinella antigen (shown by complement fixation test). The additional injection of mediators of the inflammatory reaction or their precursors, e.g., complement component C5 and arachidonic acid, caused different histological pictures. C5 produced a prolonged acute inflammatory phase with abundant neutrophils, whereas arachidonic acid did not significantly change the inflammatory response as compared to controls. The additional application of eosinophil-enriched preparation (EEP) caused a conspicuously reduced influx of monocytes/macrophages, a reduction of lymphocyte numbers, a prolonged influx of neutrophils, increased arylsulfatase activity, earlier reduction of the inflammatory process, and earlier onset of synoviocyte regeneration as compared to controls.