Interleukin-6 Production ina MurineModelofPneumocystis carinii Pneumonia: Relation toResistance and Inflammatory Response

SCIDmicebytreatment withanti-IL-6 immuno- globulin G (IgG) resulted inno significant effect on theclearance ofP.carinii (P> 0.05). Boththeserum and lungs oftreated micecontained an excessamountofanti-IL-6 IgGandlacked detectable IL-6.Theseresults suggest thatfailure toinhibit theP.carinii clearance byanti-IL-6 treatment was notduetoinsufficient administration ofantibody or incomplete neutralization ofIL-6activity. However, compared withmice receiving ratcontrol IgG,micetreated withantiIL-6 IgGhadsignificantly higher numbersofneutrophils and lymphocytes (particularly CD8+ cells) inthelunglavage fluids (P< 0.05forboth)atday19after reconstitution. Inaddition, thelevels ofbothtotal IgG(P< 0.001) andP.carinii-specific antibodies (P< 0.05) intheserum ofmicetreated withanti-IL-6 were significantly higher thanthose incontrol mice.Theseresults indicate thatalthough P.carinii infection causesbothlocal andsystemic production ofIL.6inSCIDmice, IL.6 doesnotappeartoplay acrucial role intheclearance ofP.carinii. However, itappearsthatduring resolution ofP.carinii pneumonia, IL.6plays arole intheregulation ofpulmonary inflammation andantibody responses.