INTERLEUKIN-13 ALTERS THE ACTIVATION STATE OF MURINE MACROPHAGES IN-VITRO - COMPARISON WITH INTERLEUKIN-4 AND INTERFERON-GAMMA

Interleukin (IL)-13 is a newly described cytokine expressed by activat ed lymphocytes. We examined the effects of the murine recombinant cyto kine on the phenotype and activation status of elicited peritoneal mac rophages (M Phi), concentrating on activities which are known to be mo dulated by interferon-gamma and IL-4. IL-13 markedly suppressed nitric oxide release and to a lesser extent secretion of the pro-inflammator y cytokine tumor necrosis factor-alpha. However, antimicrobial capacit y was not completely jeopardized as the respiratory burst was unaffect ed, and indeed the enhanced expression of M Phi mannose receptor and m ajor histocompatibility class II, and regulation of sialoadhesin, the M Phi sialic acid-specific receptor involved in hemopoietic and lympho id interactions, suggest that these cells are not simply deactivated, but primed for an active role in immune and inflammatory responses. Th ese activities closely mimic those of IL-4, but mediation of the effec ts by IL-4 was discounted by the use of a neutralizing monoclonal anti body. Thus, IL-13, like IL-4, is a cytokine which has complex effects on M Phi behavior, inducing activities characteristic of both activati on and deactivation.