In vivo injection of the hamster anti-murine CD3 monoclonal antibody 145 2C11 into BALB/c mice induces a massive systemic release of several cytokines. Very high circulating levels of tumor necrosis factor are detected both by enzyme-linked immunosorbent assay and L-929 bioassay 90 min following a single injection of 10 micrograms/mouse 145 2C11. Peak circulating levels of exclusively T cell-derived products such as interferon-gamma, interleukin 2 and interleukin 3 are also detected 90 min to 8 h post-injection. Importantly, this cytokine release is transient since none of these cytokines are still present 12 to 24 h post-injection. In parallel to cytokine release, 145 2C11-treated mice (10 micrograms/mouse) exhibit somnolence, hypomotility (quantified by actimetry), hypothermia, diarrhea and piloerection. At this dosage, the physical reaction is not lethal and reverses in all mice by 48 h post-injection. Severe but again reversible anatomopathological changes are also observed: massive cellular depletion, necrosis and edema of lymphoid organs, leakage syndrome and inflammatory cell infiltrates of the lung, cell vacuolization, necrosis and vascular congestion of the liver. All these data are similar to the clinical and immunological manifestations of the OKT3-induced reaction in patients and, thus, provide an invaluable experimental tool to study its mechanisms and explore its prevention.

De novo expression of TNF, IFNy, IL-3, IL4, and IL-6 genes was initiated rapidly by treatment of mice with anti-CD3. A specific feature ofthis reaction was that TNF was derived exclusively from T cells. TNF was produced both as a mature soluble trimeric protein and as a 26-kD anti-TNF-reactive protein compatible with membrane-anchored TNF. Pretreatment with anti-TNF did not affect anti-CD3-triggered TNF mRNA expression in T cells. In contrast, in vivo and in vitro anti-TNF treatment upregulated anti-CD3-induced IFNy mRNA expression and inhibited IL4 mRNA expression. These latter effects were not dependent on TNF neutralization: pretreatment with soluble recombinant 55-kD TNF receptor (TBPI) as an alternative TNF-neutralizing agent did not modify the anti-CD3-induced cytokine profile. These results suggest that a direct interaction between anti-TNF and T cell membrane-anchored TNF could account for the observed modulation of cytokine gene expression. The increased expression of INFy mRNA observed in anti-TNF-treated animals correlated with a decrease in IL-3 and IL-6 mRNA expression. Conversely, IFNy blockade by a neutralizing anti-IFNy mAb led to a substantial increase in both IL-3 and IL-6 gene expression induced by anti-CD3. Taken together, these results strongly argue for the existence, in the anti-CD3-induced cytokine cascade, of IFNy-dependent regulation of IL-3 production, which in turn modulates IL-6 production. (J. Clin. Invest. 1994. 93:2189-2196

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