Sleep has profound effects on immune function, driving T-cell migration to lymph nodes – the primary site of adaptive immunity initiation. However, scientists don’t fully understand the mechanisms that underlie links between sleep and immunity. A recent study found that immune-modulating hormones released during sleep mediate T-cell migration.

The study involved 14 healthy adults with normal sleep patterns. Participants experienced two conditions: 24 hours that included a normal night’s sleep or 24 hours of wakefulness (sleep deprivation). Researchers measured their T-cell numbers, T-cell migration, and hormone levels at various intervals throughout the 24-hour sessions.

They found that sleep (but not sleep deprivation) increased the spontaneous migration of several T-cell populations toward CCL9, a protein involved in T-cell homing toward lymph nodes. Growth hormone and prolactin (hormones produced in the pituitary gland) mediated these effects. Interestingly, heat exposure induces similar hormonal responses, suggesting that sauna use also bolsters immune function.

The findings from this small study demonstrate that sleep enhances adaptive immune function by promoting the release of immune-modulating hormones. Learn more about the effects of sleep on immunity in this episode featuring Dr. Roger Seheult.