COULD CYTOKINES ALTER NEUROVEGETATIVE FUNCTIONS IN THE BRAINSTEM? IMPLICATIONS FOR SIDS

Objectives: Polysomnographic studies reported incomplete arousal processes in infants who were victims of sudden death (SIDS). Data also suggest that alterations in sleep pattern are likely to be triggered by cytokines. Cytokines interact with neurotransmitters and alter neural function. Among the neuronal command centers in the brainstem, known to be involved in the regulation of cardio-respiratory autonomic functions are the nuclei of the solitary tract, the dorsal vagal nuclei, and the intermediate reticular zone. We previously reported IL-1 beta overexpression in specific neuronal nuclei in SIDS victims. IL-2 is another cytokine that has been described as a neuromodulator. In this study, we wanted to explore the potential involvement of this cytokine in these victims.

Methods: Tissue blocks from 19 brains ensuing from infants who succumbed to SIDS were included in this study. The brainstem was extensively explored using in situ immunohistochemical (IHC) techniques directed against cytokines including proinflammatory cytokines and IL-2.

Results: Intense immune reactivity for IL-2 was detected in a specific axonal tract, namely the tractus of the solitary nucleus, in all SIDS brains (n=19). This immune staining stood in sharp contrast against other neuronal fascicles in the brain stem. Other cytokines' expression remained compatible with our previous findings in SIDS.

Conclusion: This is the first report on the detection of Interleukine-2 cytokine in SIDS brains. It is not known if this selective expression of IL-2 in the solitary nucleus tractus implies disturbed homeostatic control of cardiorespiratory and arousal responses that seemingly underlie SIDS.