EVIDENCE AGAINST A ROLE FOR INTERLEUKIN-10 IN THE REGULATION OF GROWTH OF MYCOBACTERIUM-AVIUM IN HUMAN MONOCYTES

Interleukin-10 (IL-10) inhibits intracellular Mycobacterium avium kill ing by cytokine-activated murine macrophages and may have a role in pa thogenesis. Cytokine activities in supernatants of M. avium-infected h uman monocytes were maximal at 6-24 h for tumor necrosis factor (TNF)- alpha and 24-48 h for IL-10. TNF-alpha and IL-10 production increased with increasing M. avium-to-monocyte infection ratios (20:1 to 200:1). TNF-alpha production by monocytes infected with smooth, domed, and op aque organisms at 200:1 exceeded that of monocytes infected with smoot h, flat, and transparent M. avium (P < .01). IL-10 induction demonstra ted considerable strain-to-strain variability and did not correlate wi th intracellular M. avium growth. IL-10 significantly inhibited TNF-al pha, IL-1 beta, and IL-6 production by M. avium-infected monocytes. Co culturing monocytes with IL-10 after M. avium infection did not affect intracellular M. avium growth. Differential induction of TNF-alpha ma y be a factor in the intracellular growth of M. avium in human monocyt es. IL-10, however, played no apparent role in pathogenicity in this m odel.