The Journal of Immunology, Vol 132, Issue 1 111-113, Copyright © 1984 by American Association of Immunologists
Acquisition and extinction of conditioned suppression of a graft-vs- host response in the rat
D Bovbjerg, R Ader and N Cohen
Injection of rats with cyclophosphamide (CY) after their consumption of a
novel saccharin-flavored drinking solution results in a conditioned
aversion to saccharin and a conditioned suppression of immune responses. In
this study, female Lewis X Brown Norwegian F1 rats were conditioned by
pairing saccharin with 50 mg/kg CY. Seven weeks later (day 0), a
graft-vs-host response (GvHR) was induced in these animals by injecting
splenic leukocytes from Lewis donors into a rear footpad. At this time,
some conditioned animals were reexposed to saccharin, the conditioned
stimulus. During the 7-wk interval between conditioning and immunization,
subgroups of conditioned rats were given 0, 4, 9, or 18 extinction trials
(saccharin followed by saline injections). Animals receiving 4, 9, or 18
extinction trials showed a greater preference for saccharin on day 0 than
did animals receiving no extinction trials, but these groups did not differ
among themselves; all conditioned groups showed a lower preference for
saccharin than placebo-treated animals. There was a clear effect of number
of extinction trials on the GvHR. Animals receiving 9 or 18 extinction
trials did not differ from controls, whereas animals receiving 0 or 4
trials had a milder GvHR than did conditioned rats that were not reexposed
to saccharin at the time of immunization. These results confirm a previous
report of conditioned suppression of a GvHR, demonstrate that conditioned
immunopharmacologic responses are subject to experimental extinction, and
indicate that conditioned immunosuppression can be dissociated from
conditioned taste aversion.
