Analysis of Cytokine Expression in Rheumatoid Synovium Has
Provided New Insights Into the Pathogenesis of Rheumatoid
Arthritis and New Therapeutic Opportunities
M. Feldmann, F. Brennan, J. Bondeson, E. Paleolog, B. Foxwell, and R. Maini
W
HILE ANTIBODIES are excellent tools for the
analysis of extracellular signaling molecules and
were essential for defining the role of TNF in rheumatoid
arthritis,
1,2
another approach is needed for intracellular
pathways. We chose to use adenoviruses for a number of
reasons. These include the high efficiency of nuclear trans-
fer, effective gene expression, and their capacity (unlike
retroviruses) to infect nondividing cells. Disadvantages in-
clude potential immunogenicity and toxicity.
3
However, the cells of the immune and inflammatory
systems are not the natural hosts of adenoviruses, but since
some degree of infection of macrophages had been re-
ported by Nemerow and his colleagues,
4
we attempted to
increase the degree of infection to permit the inhibition of
responses. This was duly accomplished and has enabled us
to infect macrophages with an adenovirus overexpressing
IB, a gift of R. de Martin
5
and used to show that TNF
production was heterogeneous depending on stimulus (eg,
LPS was NFB-dependent, whereas zymosan and anti-
CD45 were not).
6
This opened up the possibility of evalu-
ating whether TNF production due to the rheumatoid
process might differ from that which drives protective
TNF production, for example, in response to an infectious
disease. This question is important because while anti-
TNF antibody therapy in the short term is not strongly
proinfective, as judged by the limited clinical trial experi-
ence, it may be different in the long term. Hence it is of
interest to establish whether TNF regulation in disease is
regulated in another manner from “immune” TNF.
For this purpose, we have developed a T-cell macrophage
coculture system based on the one described by Dayer and
colleagues
7
and have used it to compare a number of T-cell
populations. These included T cells purified from rheuma-
toid synovium without further stimulation, blood T cells
stimulated with anti-CD3 representing T cells responding to
an antigen, and also a population of T cells stimulated with
a cocktail of T-cell activating cytokines, namely IL-6 and
TNF (which up-regulate CD25) and IL-2, or IL-15. These
cytokine-activated T cells were first described by Unutmaz
et al
8
to activate B lymphocytes to produce Ig. We subse-
quently showed that they activate monocytes to produce an
unbalanced proinflammatory cytokine profile with TNF
but not IL-10.
9
In these T-cell/macrophage cocultures, we found that all
three populations of cells induced TNF. In all instances,
the conductive signal depended on a cell contact interac-
tion, as cell impermeable membranes inhibited them. To
evaluate whether the T-cell-derived contact signals were
comparable, the monocyte population was infected with
adenovirus overexpressing IB or a control virus prior to
interaction with either of these T cells. It was found that
anti-CD3-stimulated T-cell-induced TNF was not inhibited,
while that induced by rheumatoid synovial T cells and
cytokine-activated T cells was not.
This indicates that TNF regulation differs in rheumatoid
synovium from that in normal immune response.
10
CONCLUSIONS
While we know that TNF blockade is a useful therapeutic
target, we do not yet know what is the best way to block
TNF action by small, chemical, orally available drugs. Using
adenoviruses as a tool to block pathways in normal cells, it
is possible to study this problem in a novel way. It has also
provided data that indicates heterogeneity of TNF pro-
duction and some differences between “pathological” TNF
produced in rheumatoid synovium and that produced in a
normal immune response.
ACKNOWLEDGMENT
This work was chiefly funded by the Arthritis Research Campaign,
UK.
REFERENCES
1. Feldmann M, Brennan FM, Maini RN: Annu Rev Immunol
14:397, 1996
2. Feldmann M, Elliott MJ, Woody JN, et al: Advances in
Immunology 64:283, 1997
3. Shenk T: In Fields BN, Knipe DM, Howley PM (eds):
Fundamental Virology, 3rd ed. Philadelphia: Lippincott-Raven
Publishers; 1996, p 2111
4. Huang S, Endo RI, Nemerow GR: J Virol 69:2257, 1995
From the Kennedy Institute of Rheumatology, London, UK.
Address reprint requests to Dr M Feldmann, Kennedy Insti-
tute, 1 Aspenlea Road, London S6 8LH, UK.
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