[The formation of infliximab and anti-infliximab immune complexes as an explanation for non-responding to infliximab treatment of rheumatoid arthritis: observational study in 4 patients].
OBJECTIVE
To investigate the in vivo mechanism of non-responding to infliximab treatment of patients with rheumatoid arthritis (RA) and the role of anti-infliximab antibodies by using radiolabeled infliximab.


METHODS
Descriptive and comparative study.


METHODS
Two responding and two non-responding RA patients were infused with radiolabeled infliximab. Subsequently imaging investigations and serum analysis were performed at set times.


RESULTS
The scintigrams showed that the labelled infliximab was mainly present in the blood until 24 h after infusion. There was a trend of faster blood clearance and higher liver and spleen uptake of 99mTc-infliximab in one non-responding patient. Labelled infliximab was taken up by inflamed joints. The anti-infliximab level was high (1008 and 1641 U/ml) in the non-responders and low or not detectable in the responders. Sucrose gradients of serum revealed antibody complexes in both non-responders. Various sizes of antibody complexes, including very large ones, were observed in one non-responder who developed a serious infusion reaction.


CONCLUSIONS
Infliximab-anti-infliximab immune complexes were found to form in RA non-responders due to the presence of significant quantities of anti-infliximab. This finding may partly explain the failure of the infliximab treatment.
van der Laken
C J
CJ
Afd. Reumatologie, VU Medisch Centrum, Amsterdam. j.vanderlaken@vumc.nl
Voskuyl
A E
AE
Roos
J C
JC
Stigter van Walsum
M
M
de Groot
E R
ER
Wolbink
G J
GJ
Dijkmans
B A C
BA
Aarden
L A
LA