Role of the Immune System in Autism Spectrum Disorders (ASD).

BACKGROUND: The evidence based supports that multifactorial and complex immune interactions play a role in autism spectrum disorders (ASD), but contradictory findings are also reported. OBJECTIVE: The aim of this selective review was to identify trends in the research literature on this topic, focusing on immunology and other aberrations with respect to the different ASD subtypes. METHODS: This selective review is based on original and review articles written in English and identified in literature searches of PubMed. RESULTS: Several studies have found that the risk of ASD is greater among children whose mothers suffered from autoimmune diseases while pregnant. Moreover, individuals with ASD show increased levels of antibodies that are specific for several specific proteins. Studies also show that mothers of children with ASD have antibodies against fetal brain proteins. There are also reports on the associations between increased levels of proinflammatory cytokines and ASD. Finally, infections in mothers during pregnancy are linked to an increased risk of ASD. CONCLUSION: We propose that the large inconsistencies in findings among studies in the field are due to differences in subdiagnoses among the included children with ASD. Well-phenotyped ASD samples are needed to understand the biological and immunological mechanisms underpinning ASD and its subdiagnoses. Future research should apply new strategies to scrutinize the link between ASD and changes in immune responsivity. Important new research avenues are to investigate the associations (a) between different ASD phenotypes and aberrations in (auto)immune pathways and (b) between reduced natural regulatory autoimmune responses during pregnancy, which are in turn associated with increased oxidative and nitrosative stress in maternal blood and putative detrimental effects in the offspring.

Serum Tryptophan, Tryptophan Catabolites and Brain-derived Neurotrophic Factor in Subgroups of Youngsters with Autism Spectrum Disorders.

BACKGROUND: There is evidence that changes in neuro-immune responses coupled with dysfunctions in serotonin metabolism underpin the pathophysiology of autism spectrum disorders (ASD). OBJECTIVE: This study aimed to delineate whether ASD subgroups or characteristics show aberrations in tryptophan and brain-derived neurotrophic factor (BDNF) metabolism. METHODS: 65 individuals with ASD (diagnosed according to ICD criteria) and 30 healthy control patients were included. Measured were serum levels of tryptophan, kynurenine (KYN), kynurenic acid (KA), quinolinic acid (QA), BDNF and PRO-BDNF and total blood 5-HT and 5-OH-tryptophan (5-HTP). RESULTS: Elevated BDNF levels and lower tryptophan and KA levels were characteristics of both childhood autism and intellectual disability disorder, whilst elevated tryptophan and lower 5-HT synthesis were hallmarks of Asperger syndrome. A pathological MRI was associated with elevated tryptophan and lowered KA. Abnormal EEG results and dysmorphology were both associated with an elevated BDNF/ PRO-BDNF ratio. Any brain pathology and gastro-intestinal symptoms were accompanied by lowered KA. CONCLUSIONS: Increased BDNF production and changes in the metabolism of tryptophan are associated with many ASD characteristics, showing particularly strong associations with childhood autism and Intellectual and Developmental Disabilities. Peripheral BDNF and tryptophan metabolism appear to take part in the pathophysiology of autism spectrum disorders and their phenotypes.

Kynurenine Pathway in Autism Spectrum Disorders in Children.

BACKGROUND: There is increasing evidence that altered immune responses play a role in the pathogenesis of autism spectrum disorders (ASD), together with dysfunction of the serotonergic and glutamatergic systems. Since the kynurenine (KYN) pathway that degrades tryptophan (TRP) is activated in various neuroinflammatory states, we aimed to determine whether this pathway is activated in ASD. METHODS: Sixty-five pediatric ASD patients (including 52 boys) were enrolled from an epidemiological survey covering 2 counties in Norway; 30 (46.5%) of these patients were diagnosed with childhood autism, 16 (24.6%) with Asperger syndrome, 12 (18.5%) with atypical autism, 1 (1.5%) with Rett syndrome, and 6 (9.2%) with other ASD. The serum levels of the following markers were measured in the children with ASD and compared to those in 30 healthy children: TRP, KYN, kynurenic acid (KA), 3-hydroxykynurenine, and quinolinic acid. RESULTS: The mean serum level of KA was significantly lower in the ASD group than in the healthy controls (28.97 vs. 34.44 nM, p = 0.040), while the KYN/KA ratio was significantly higher in the ASD group (61.12 vs. 50.39, p = 0.006). The same relative values were found when comparing the childhood autism subgroup with the controls. Also, the mean serum level of TRP was significantly lower in children with a subdiagnosis of childhood autism than in those with Asperger syndrome (67.26 vs. 77.79 µM, p = 0.020). CONCLUSION: Our study indicates that there is an increased neurotoxic potential and also a possible lower KYN aminotransferase activity in ASD.

Cytokine Profile in Autism Spectrum Disorders in Children.

The pathogenesis of autism spectrum disorders (ASD) is not completely understood, but there is evidence of associations with altered immune responses. The aim of this study was to determine the serum levels of various cytokines in children with ASD and in healthy controls, in order to determine their role in ASD and its diagnostic subgroups. Sixty-five ASD patients were enrolled from an epidemiological survey in Norway, of which 30 were diagnosed with childhood autism, 16 with Asperger syndrome, 12 with atypical autism, 1 with Rett syndrome, and 6 with another ASD diagnosis. The serum levels of 12 cytokines were measured in all of the patients and in 30 healthy children. The cytokine levels did not differ significantly between the ASD group and the healthy controls. However, the interleukin-8 (IL-8) level was significantly higher (6.82 vs 4.58 pg/ml, p = 0.017) while that of IL-10 was significantly lower (2.24 vs 6.49 pg/ml, p = 0.009) in patients with childhood autism than in controls. Furthermore, the IL-8 level was significantly higher in childhood autism than in Asperger syndrome (6.82 vs 4.05 pg/ml, p = 0.013). Our study shows that the cytokine profile of children diagnosed with ASD, regardless of the subdiagnosis, does not differ from healthy controls. However, differentiation into different diagnostic subgroups reveals significantly different levels of IL-8 and IL-10. This indicates that different mechanisms may underlie the different ASD subdiagnoses. Future research into the pathophysiological mechanisms of ASD should pay more attention to the different subdiagnoses of ASD.

A recurrent deletion on chromosome 2q13 is associated with developmental delay and mild facial dysmorphisms.

We report two unrelated patients with overlapping chromosome 2q13 deletions (patient 1 in chr2:111415137-113194067 bp and patient 2 in chr2:110980342-113007823 bp, hg 19). Patient 1 presents with developmental delay, microcephaly and mild dysmorphic facial features, and patient 2 with autism spectrum disorder, borderline cognitive abilities, deficits in attention and executive functions and mild dysmorphic facial features. The mother and maternal grandmother of patient 1 were healthy carriers of the deletion. Previously, 2q13 deletions were reported in 27 patients, and the interpretation of its clinical significance varied. Our findings support that the 2q13 deletion is associated with a developmental delay syndrome manifesting with variable expressivity and reduced penetrance which poses a challenge for genetic counselling as well as the clinical recognition of 2q13 deletion patients.

Children with autism spectrum disorders - the importance of medical investigations.

BACKGROUND: Considerable knowledge about medical comorbidity in cases of Autism Spectrum Disorders (ASD) is available, still it is not well established how extensive the medical investigations should be in individual cases. The aim is to explore proportions of possible specific medical conditions in ASD. METHODS: 79 subjects went through extensive medical evaluations according to pre-defined procedures, including medical and developmental history, physical and biomedical investigations. RESULTS: Clinical neurological findings were quite common, and we found a high number of pathological findings in the additional medical investigations. Our study revealed that these pathological deviations occurred more frequently in patients with childhood autism than in the other diagnostic sub-groups, the exception were chromosomal findings which occurred more often in patients not-diagnosed with childhood autism. CONCLUSION: Medical and laboratory investigations should still be performed as a consequence of the patient's history, clinical presentations or family history. We should basically continue the use of non-routine and invasive procedures which do not put the patient at some unnecessary risk, in the absence of relevant clinical indications.