Can we use conditioning to boost our immune system?

How hijacking our immune response could lead to future medical treatments

Farid Alsabeh


An artist’s rendition of various cells of the immune system (Source)

At chemotherapy treatment centers, healthcare professionals tell a common anecdote. Patients will often experience nausea while being treated with chemotherapeutic drugs. But for some, the nausea comes prematurely: the simple act of sitting down for the treatment can trigger it.

The explanation for this ‘anticipatory nausea’ is most likely conditioning. Over the course of several months, the patient repeats the routine of sitting in the same room, receiving a drug, and becoming nauseous. Eventually, the environment alone is enough to bring about their nausea.

If conditioning is powerful enough to cause nausea, can it be used for positive outcomes — for example, to boost our immune systems? In this article, we’ll explore how a study conducted by Longo et al. (1999) suggests that we can do exactly such a thing, opening the door to a new world of medical treatments.

Immune conditioning

The basic components of conditioning can be explained using Pavlov’s famous dogs. A serving of meat acts as the unconditioned stimulus, which evokes salivation, the unconditioned response. The sound of a bell acts as the conditioned stimulus, which after being paired enough times with the serving of meat, is sufficient to trigger the salivation on its own.

Immune conditioning follows the same logic. An immunologically-active agent acts as the unconditioned stimulus, which evokes an immune response, the unconditioned response. A neutral agent acts as the conditioned stimulus, which after being paired enough times with the immunologically-active agent, is sufficient to trigger the immune response on its own.

The pairing of the immunologically-active agent, represented by the biceps, with a neutral agent, the tea, eventually makes it so that the neutral agent alone elicits an immune response

In this study, the immunologically-active agent was recombinant human interferon gamma, or rhIFN- γ (IFN), which when injected stimulates the immune system. The benign agent was propylene glycol (PG), an inert but distinctly-flavored solution administered orally.