Host factors in the formation of abscesses.

The role of host factors in the formation of subcutaneous abscesses due to Bacteroides fragilis or Staphylococcus aureus was investigated in athymic nude mice, mice deficient in the fifth component of complement (C5D), and mice pretreated with cobra venom factor (CVF). CVF-treated mice, inoculated with B. fragilis, had abscesses 62% larger than those of control mice at day 4 (P < 0.01), but no significant difference was observed when S. aureus was used. Athymic nude mice had significantly smaller abscesses than control animals at both days 4 and 7 after inoculation with either organism. There were no differences in abscess size or in the accumulation of neutrophils at day 4 when C5D mice were compared with control animals for either organism. The results suggested that the activity of the alternative complement pathway may influence abscess size and that chemotactic factors other than the fifth component of complement can supervene in C5D mice to produce encapsulated abscesses. The absence of thymic factors did not prevent containment of abscesses.