J Pediatr. 2005 May;146(5):582-4. 
Evaluation of an association between gastrointestinal symptoms and 
cytokine production against common dietary proteins in children
 with autism spectrum disorders (ASD)

 A high prevalence of elevated TNF-alpha/IL-12 production by GI 
(+) ASD PBMCs with CMP and its major components indicates a role of 
NFH (NON-ALLERGIC FOOD HYPERSENSITIVITY) in GI symptoms observed in children with ASD.
(Translation:  They found evidence of gut symptoms and immune activation
 in autistic children, a "hypersensitivity" but not the classic allergy)

Cincinnati Children's Hospital Medical Center --- May 2004

-- A new Cincinnati Children's Hospital Medical Center study 
provides further evidence of a link between autism and 
immunologic disorders, including allergy. The study, 
although preliminary, indicates that children with autism 
may have an increased prevalence
 of allergic disorders, particularly of the
 gastrointestinal system. 
 
Centre for Paediatric Gastroenterology, Royal Free and University College, Medical School, London
 Inflammatory intestinal pathology has been reported in children with regressive autism 
(affected children).   Detailed analysis of intestinal biopsies in these children indicates a novel lymphocytic enterocolitis 
with autoimmune features; however, links with cognitive function remain unclear.
 To characterize further, the nature and extent of this disease we examined the mucosal infiltrate 
using flow cytometry
 
 
 J Clin Immunol. 2003 Nov;23(6):504-17.
 
 
Autism Foundation and a select group of doctors and scientists in Portland
in Autumn, 2001.
 
More than 50% of autistic children appear to have GI symptoms, food
allergies, and maldigestion/malabsorption issues.  We need large,
evidence-based studies need to be done in order to fully understand the
gut-brain association in autism.