Neuro-Immune Associative Learning

Excerpt

Experimental evidence demonstrates intensive and extensive interactions between the nervous and immune systems. The central capacity of associating a certain immune response or status (allergen, toxin, antigen) with a specific stimulus (environment or flavor) seems to be of high adaptive value; this special kind of associative learning may have been acquired as an adaptive strategy during evolution in order to protect an organism and/or prepare it for danger. Furthermore, it is possible that, depending on the different environmental challenges, the species formed species-specific associations during evolution.

Classical conditioning or associative learning is often described as the transfer of the response-eliciting property of a biologically significant stimulus (unconditioned stimulus; US) to another stimulus (conditioned stimulus; CS) without that property. This transfer is thought to occur only if the CS serves as a predictor of the US. Thus, classical conditioning can be understood as learning about the temporal or causal relationships between external and internal stimuli, to allow for the appropriate preparatory set of responses before biologically significant events occur.

Regarding neuro-immune associative learning (NIAL), an immunomodulatory stimulus (antigen, immunomodulating drug) is employed as an US and paired with a neutral stimulus. After this associative phase, the neutral stimulus becomes a CS that can modify the immune response on demand (conditioned response; CR). The influence of NIAL on immune responses has been reviewed several times. However, in this chapter we propose an innovative approach, pointing out the biological meaning and possible clinical implications of neuro-immune associative learning. Furthermore, after analyzing the available literature, we propose a general theoretical framework for this special kind of associative learning.