Interleukin 12 is produced in vivo during endotoxemia and stimulates synthesis of gamma interferon.
Gamma interferon (IFN-gamma) is produced in response to circulating lipopolysaccharide (LPS) and contributes to the lethality of endotoxic shock. To address the cellular source of IFN-gamma production in vivo, T cells and B cells were magnetically purified from C57BL/6 mouse spleens 5 h following endotoxin injection. IFN-gamma RNA was abundant in splenic CD4+ and CD8+ T cells and in a T- and B-cell-depleted population of splenocytes containing 34% NK1.1+ natural killer (NK) cells. Because interleukin 12 (IL-12) is a known inducer of IFN-gamma synthesis by cultured T cells and NK cells, we examined whether IL-12 might be involved in IFN-gamma release during endotoxemia. mRNA encoding the p40 subunit of IL-12 increased markedly in the spleens of C57BL/6 mice at 2 h after LPS injection, whereas p35 IL-12 mRNA was constitutively expressed at all times. Bioactive IL-12 (p70 heterodimer) was detected in mouse serum at 2 to 4 h after LPS injection. Similar results were obtained using a p40 subunit-specific enzyme-linked immunosorbent assay. Endotoxin-insensitive C3H/HeJ mice generated threefold less IL-12 p70 and IFN-gamma at these times than endotoxin-sensitive C3H/HeOuJ mice. Pretreatment of mice with polyclonal anti-mouse IL-12 antibody reduced IFN-gamma levels present at 6 h post-LPS nearly sixfold in three separate experiments. These studies support a role for IL-12 as a proximal stimulator of IFN-gamma release during endotoxemia.
Heinzel
F P
FP
Cleveland VA Medical Center, Ohio 44106.
Rerko
R M
RM
Ling
P
P
Hakimi
J
J
Schoenhaut
D S
DS
D000818:Animals; D004731:Endotoxins / Q000097:blood*; D005260:Female; D006041:Goats; D007371:Interferon-gamma / Q000096:biosynthesis* / Q000235:genetics; D018664:Interleukin-12 / Q000096:biosynthesis* / Q000235:genetics; D007694:Killer Cells, Natural / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000032:analysis; D013601:T-Lymphocytes / Q000378:metabolism
D004731:Endotoxins; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D018664:Interleukin-12; D007371:Interferon-gamma