One-trial conditioning of the antibody response to hen egg lysozyme in rats

In Wistar rats, reexposure to a novel conditioned stimulus (CS) previously paired with a protein antigen, hen egg lysozyme (HEL) on a single condition ing trial increased anti-MEL Ige levels relative to conditioned rats that w ere not reexposed to the CS, conditioned rats that were preexposed to the C S, and nonconditioned rats. These results confirm previous findings that a single exposure to a CS associated with immunization is sufficient to elici t an antibody response upon subsequent reexposure to the CS in the absence of exogenous antigen. (C) 2001 Elsevier Science B.V. All rights reserved.