Gamma-interferon is the factor in lymphokine that activates human macrophages to inhibit intracellular Chlamydia psittaci replication.
We have demonstrated previously that mitogen-induced lymphokines activate human monocyte-derived macrophages to inhibit the intracellular replication of Chlamydia psittaci. To identify the factor(s) in crude lymphokines responsible for this antimicrobial effect, we tested human Con A-induced lymphokines for interferon activity. We also attempted to neutralize the lymphokines with a monoclonal antibody directed against human gamma-interferon and examined the ability of partially purified human gamma-interferon to induce macrophage antichlamydial activity. The lymphokine-induced antichlamydial effect was measured by the inhibition of chlamydial inclusion formation in Giemsa-stained macrophage cultures. Our lymphokines were found to be rich in gamma-interferon; treatment of cells for 48 hr before infection with lymphokines containing 300 U/ml of interferon resulted in an 89% inhibition of chlamydial growth. This lymphokine effect was completely abolished by monoclonal antibody against human gamma-interferon, but not by antisera against human alpha- or beta-interferons. In addition, partially purified human gamma-interferon alone induced macrophages to restrict chlamydial growth by 95%. We conclude that it is the gamma-interferon present in human Con A-induced lymphokines that activates monocyte-derived macrophages to inhibit chlamydial replication.
D000911:Antibodies, Monoclonal / Q000276:immunology; D002691:Chlamydophila psittaci / Q000254:growth & development; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D002479:Inclusion Bodies / Q000382:microbiology; D007371:Interferon-gamma / Q000276:immunology / Q000502:physiology*; D008222:Lymphokines / Q000032:analysis*; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology / Q000382:microbiology; D008970:Molecular Weight; D009956:Psittacosis / Q000276:immunology / Q000382:microbiology*
D000911:Antibodies, Monoclonal; D008222:Lymphokines; D007371:Interferon-gamma