Cytokine profiles by peripheral blood monocytes are associated with changes in behavioral symptoms following immune insults in a subset of ASD subjects: an inflammatory subtype?

BACKGROUND

Some children with autism spectrum disorders (ASD) are characterized by fluctuating behavioral symptoms following immune insults, persistent gastrointestinal (GI) symptoms, and a lack of response to the first-line intervention measures. These children have been categorized as the ASD-inflammatory subtype (ASD-IS) for this study. We reported a high prevalence of non-IgE mediated food allergy (NFA) in young ASD children before, but not all ASD/NFA children reveal such clinical features of ASD-IS. This study addressed whether behavioral changes of ASD-IS are associated with innate immune abnormalities manifested in isolated peripheral blood (PB) monocytes (Mo), major innate immune cells in the PB.

METHODS

This study includes three groups of ASD subjects (ASD-IS subjects (N = 24), ASD controls with a history of NFA (ASD/NFA (N = 20), and ASD/non-NFA controls (N = 20)) and three groups of non-ASD controls (non-ASD/NFA subjects (N = 16), those diagnosed with pediatric acute onset-neuropsychiatric syndrome (PANS, N = 18), and normal controls without NFA or PANS (N = 16)). Functions of purified PB Mo were assessed by measuring the production of inflammatory and counter-regulatory cytokines with or without stimuli of innate immunity (lipopolysaccharide (LPS), zymosan, CL097, and candida heat extracts as a source of β-lactam). In ASD-IS and PANS subjects, these assays were done in the state of behavioral exacerbation ('flare') and in the stable ('non-flare') condition. ASD-IS children in the 'flare' state revealed worsening irritability, lethargy and hyperactivity.

RESULTS

'Flare' ASD-IS PB Mo produced higher amounts of inflammatory cytokines (IL-1β and IL-6) without stimuli than 'non-flare' ASD-IS cells. With zymosan, 'flare' ASD-IS cells produced more IL-1β than most control cells, despite spontaneous production of large amounts of IL-1ß. Moreover, 'flare' ASD-IS Mo produced less IL-10, a counterregulatory cytokine, in response to stimuli than 'non-flare' cells or other control cells. These changes were not observed in PANS cells.

CONCLUSIONS

We observed an imbalance in the production of inflammatory (IL-1ß and IL-6) and counterregulatory (IL-10) cytokines by 'flare' ASD-IS monocytes, which may indicate an association between intrinsic abnormalities of PB Mo and changes in behavioral symptoms in the ASD-IS subjects.