utilized as a transgene, indicates the anatomic loca- 
tions of TNF biosynthesis in healthy animals and in 
animals subjected to various types of invasive stim- 
uli or stress. 
With the transgene as a guide, it has been possible 
to demonstrate that TNF is synthesized within the 
thymus and within the trophoblast of normal mice 
but in no other tissues examined to date. On the 
other hand, if mice are injected with bacterial endo- 
toxin, many tissues express the transgene. This pro- 
vides evidence that numerous cell types, rather than 
simply cells of lymphoreticular origin, are capable 
of responding to endotoxin. Moreover, since the 
transgene seems to be limited in its accessibility 
much as the authentic TNF gene is, it would seem 
probable that those tissues that express CAT also ex- 
press TNF. Immunohistochemical staining of tissues 
that express CAT activity will hopefully reveal the 
cell types responsible for TNF biosynthesis within 
specific tissues. 
In addition to endotoxin, other stimuli are known 
to activate TNF biosynthesis. Ultraviolet (UV) irra- 
diation has been shown to cause TNF expression in 
keratinocytes. Dr. Beutler and his colleagues have 
now shown that, unlike endotoxin, which depends 
on NF-/cB elements within the promoter for trans- 
duction of its effect on TNF gene transcription, UV 
light works its effect through very proximal ele- 
ments within the promoter, only 109 base pairs re- 
moved from the cap site. Further mapping studies 
may reveal the UV-responsive element within the 
TNF gene. 
Predictably, UV irradiation induces expression of 
the CAT reporter transgene when transgenic mice 
are exposed to it. Shiga-like toxin, the etiologic 
agent in the hemolytic uremic syndrome, has been 
shown specifically to induce expression of the 
transgene in renal tissue. Thus it would seem feasi- 
ble to use transgenic mice bearing the CAT reporter 
gene as a means of identifying signals responsible 
for tissue-specific TNF synthesis and for charting the 
expression of TNF in vivo in the course of various 
diseases. 
Recombinant inhibitors of TNF bioactivity have 
been designed and produced in Dr. Beutler's labora- 
tory, to probe the biological function of TNF in 
vivo. The inhibitors are chimeric proteins in which 
the TNF receptor extracellular domains are cova- 
lently linked to an IgG heavy chain. Such inhibitors 
are of low antigenicity, block the biological activity 
of TNF more effectively than monoclonal antibod- 
ies, and circulate with a long half-life in vivo. Pre- 
liminary studies indicate that the inhibitors are capa- 
ble of crossing the placenta and have shown that 
their administration is compatible with completion 
of pregnancy. These findings raise questions con- 
cerning the function of TNF produced by the tropho- 
blast. Transgenic mice expressing the TNF inhibi- 
tors have been produced and may be shown, at term, 
to express anti-TNF activity in the plasma compart- 
ment. Studies of the phenotype of such animals, and 
in particular of their responses to various disease 
processes, have now been initiated. 
The projects described above were partly sup- 
ported by the National Institutes of Health and by a 
grant from the American Cancer Society. 
Dr. Beutler is also Associate Professor of Inter- 
nal Medicine at the University of Texas Southwest- 
ern Medical Center at Dallas. 
Books and Chapters of Books 
Beutler, B., and Beutler, S. 1992. The pathogenesis 
of fever. In Cecil Textbook of Medicine (Wyn- 
gaarden, J.B., Smith, L.H., and Bennett, J. C, Eds.). 
Philadelphia, PA: Saunders, pp 1568-1571. 
Beutler, B., and Cerami, A. 1992. Introduction. In 
Tumor Necrosis Factors: The Molecules and 
Their Emerging Role in Medicine (Beutler, B., 
Ed.). New York: Raven, pp 1-10. 
Beutler, B., Han, J., Kruys, V., and Giroir, B.P. 
1992. Coordinate regulation of TNF biosynthesis 
at the levels of transcription and translation: pat- 
terns of TNF expression in vivo. In Tumor Necro- 
sis Factors: The Molecules and Their Emerging 
Role in Medicine (Beutler, B., Ed.). New York: 
Raven, pp 561-574. 
Articles 
Beutler, B. 1992. Application of transcriptional 
and posttranscriptional reporter constructs to the 
analysis of tumor necrosis factor gene regulation. 
Am J Med Sci 5Q5:\29-W. 
Giroir, B P., and Beutler, B. 1992. Effect of amrin- 
one on tumor necrosis factor production in endo- 
toxic shock. Circ Shock 36:200-207. 
Giroir, B., Brown, T., and Beutler, B. 1992. Con- 
stitutive synthesis of tumor necrosis factor in the 
thymus. Proc Natl Acad Sci USA 89:4864-4868. 
Han, J.H., Beutler, B., and Huez, G. 199 1 . Complex 
regulation of tumor necrosis factor mRNA 
turnover in lipopolysaccharide-activated macro- 
phages. Biochem Biophys Acta 1090:22-28. 
Kruys, V., Kemmer, K., Shakhov, A , Jongeneel, V., 
and Beutler, B. 1992. Constitutive activity of the 
tumor necrosis factor promoter is canceled by the 
3' untranslated region in nonmacrophagc cell 
CELL BIOLOGY AND REGULATION 23 
