Plasma cytokine levels in children with autistic disorder and unrelated siblings

Abstract

Background: The pathogenesis of autistic disorder (AD) is not clearly understood but genetic factors and the immune system have been implicated. Disturbed immunoglobulin levels and autoantibodies to neuronal elements have been reported in AD including cytokines encoded by genes involved with cell proliferation, migration and adhesion but there is a paucity of data comparing cytokine levels in children with AD and unrelated siblings without AD.

Methods: We analyzed 39 plasma cytokines in 99 well-characterized children with AD between 5 and 10 years of age and 40 age and gender matched healthy unrelated siblings without AD under the same clinical assessments, specimen processing and laboratory conditions. Multiplex sandwich immunoassays were used with the Luminex fluorescent-bead based platform. Log-transformed values of the 29 cytokines meeting laboratory criteria for inclusion were analyzed by analysis of covariance with a general linear model adjusting for diagnosis, gender, diagnosis by gender interaction effects, age and days of specimen handling. The Tukey-Kramer post hoc test was used to control for multiple comparisons.

Results: Eight of 29 cytokine levels analyzed were significantly lower in children with AD compared with unrelated siblings without the diagnosis of AD. Three of the cytokines are known to be involved with hematopoiesis and five with attraction of T-cells, natural killer cells and monocytes.

Conclusions: Plasma cytokine levels representing chemokines involved in the T-helper cell immune system and hematopoiesis were lower in the children with AD compared with unrelated siblings without AD necessitating further studies to confirm immunological disturbances influencing hematopiesis and antibody production in the children with AD. Linking genes that encode immune related proteins and cytokines are important to study for their impact on critical periods of brain development and function.

Fig. 1.

Raw data and statistical results for each of the 29 analyzable cytokines meeting the laboratory requirements for inclusion. (A) Grouped by diagnosis and (B) grouped by gender. Significant values are indicated: ^*p < 0.05; ^†p < 0.01.

Fig. 2.

Cytokine levels, fold change by diagnosis. Individual cytokine data points from children with AD represented as fold change in relationship to controls. Subjects with AD (N = 99) and unrelated, unaffected siblings (N = 40). Significant values (in bold) are indicated: ^ap < 0.05; ^bp < 0.01.

Fig. 3.

Representative box plots from selected cytokines in subjects grouped by diagnosis. Box plots represent median (junction between light and dark shading) and interquartile ranges (25% range, light shading; 75% range, dark shading). Bars represent maximum and minimum values from log transformed data for each group.

Fig. 4.

Cytokine levels, fold change by gender. Individual cytokine data points from males (AD and control) represented as fold change in relationship to females (AD and control). Males (N = 102) and females (N = 37). Significant values (in bold) are indicated: ¹p < 0.05; ²p < 0.01.