Our Findings on Autism
  • Increased microglial and astroglial activation is present in the
    brain of patients with autism
    Our analysis of the neuropathological changes in brain tissues of autistic patients revealed extensive neuroglial responses characterized by microglial and astroglial activation. As compared to normal controls, GFAP immunostaining in three brain regions of the autistic brains (frontal cortex, cingulate gyrus and cerebellum) revealed increased astroglial reactions characterized by an increase in the volume of perikarya and glial processes. In the brains of autistic patients, GFAP immunostaining of the cerebellum showed a marked reactivity of the Bergmann's astroglia in areas of Purkinje cell loss within the PCL, as well as a marked astroglial reaction in the GCL and cerebellar white matter (Astroglia in cerebellum of autistic brain). Microglial activation in autistic brains was further characterized by immunocytochemical staining for MHC class II markers (HLA-DR). Marked microglial activation was observed in the cerebellum, cortical regions and white matter of autistic patients (Microglia in autism). The most prominent microglial reaction was observed in the cerebellum, where the immunoreactivity for HLA-DR showed a significantly higher fractional area of immunoreactivity in both the GCL and cerebellar white matter of autistic subjects than in controls.
  • Cerebellum is one of the most affected regions in the brain regions in autism
    In our studies of brains of autistic patients, the most prominent histologic changes were observed in the cerebellum, characterized by a patchy loss of neurons in the Purkinje cell layer (PCL) and granular cell layer (GCL) (Cerebellum in autism)
  • There is a lack of evidence of adaptive immune responses in the brain of autistic patients
    An examination of immunopathological reactions associated with adaptive immunity in the brain of autistic patients was carried out by immunocytochemical studies to identify T- and B-lymphocyte infiltration and deposition of immunoglobulin and complement, as indicators of cellular and humoral immune responses. We observed a few isolated perivascular CD3+ and CD20+ cells in both autistic and control brains but saw no evidence of leptomeningeal, parenchymal, or perivascular inflammatory infiltration in autistic brains in any of the regions studied. There was no evidence of IgG, IgA, or IgM deposition in neuronal or neuroglial cell populations.
  • There is an increased level of pro-inflammatory cytokines and chemokines in different cortical and subcortical regions
    We assessed the profiles of expression of proteins involved in inflammatory pathways by cytokine protein array methodology in brain tissue homogenates from autistic (n=7) and control (n=7) patients. A statistical analysis of the relative expression of cytokines in autistic and control tissues showed a consistent and significantly higher level of subsets of cytokines in the brains of autistic patients: the anti-inflammatory cytokine tumor growth factor ß1 (TGF-ß1) was increased in the frontal cortex (P=0.026), cingulate cortex (P=0.011) and cerebellum (P=0.035), and the pro-inflammatory chemokines, macrophage chemoattractant protein-1 (MCP-1) and thymus and activation-regulated chemokine (TARC), were increased in the cingulate cortex (P=0.026 and 0.035, respectively) and cerebellum (P=0.026 and 0.035, respectively). Only insulin-like growth factor binding protein-1 (IGFBP-1), a growth and differentiation factor involved in immune and cellular growth pathways, was consistently increased in the cortical regions (frontal, P= 0.038; cingulate, P=0.011), but the difference did not reach statistical significance in the cerebellum (P= 0.11). Interestingly, a larger spectrum of increased pro-inflammatory and modulatory cytokines was seen in the cingulated cortex, where there was a significant increase in interleukin-6 (IL-6), interleukin-10 (IL-10), macrophage chemoattractant protein-3 (MCP-3), eotaxin, eotaxin 2, macrophage-derived chemokine (MDC), chemokine-ß8 (Ckß8.1), neutrophil activating peptide-2 (NAP-2), monokine induced by interferon-γ (MIG), B-lymphocyte chemoattractant (BLC), leptin and osteoprotegerin.
  • Reactive neuroglial cells are the main source of cytokines and chemokines in the brain of autistic patients To determine the cellular sources of the most significantly increased cytokines in the brains of autistic patients, we carried out immunocytochemical staining for TGF-ß1, MCP-1, IGFBP-1, and IL-6 in the MFG, ACG and CBL. The staining patterns observed indicated that astrocytes were the main source of both MCP-1 and IL-6. Both cytokines were prominently expressed in reactive astrocytes in the cerebellum and cortical and subcortical white matter regions. It is noteworthy that TGF-ß1 and IGFBP-1 expression was seen not only in reactive astrocytes but also in the Purkinje cell population and in subsets of GCL cells in the CBL. Some microglial cells were also labeled with the antibodies recognizing TGF-ß1 and IGFBP-1. Purkinje cells with degenerative changes appeared strongly immunoreactive for TGF-ß1.
  • The cerebrospinal fluid from patients with autism shows the fingerprints of inflammatory reactions Since brain tissues from patients with autism showed a prominent pro-inflammatory profile, we also studied CSF from autistic patients to determine its cytokine inflammatory profile. Cytokine protein arrays were used to compare the cytokine profiles of CSF from 6 autistic patients to that of CSF from a pool of donors without CNS pathology or inflammatory disorders (e.g., pseudotumor cerebri or headaches). As we had observed in brain tissue, CSF from autistic patients showed a significant increase in MCP-1 (12 fold increase) when compared to controls. There were no differences in expression of TARC or TGF-ß1 in the CSF. However, other pro-inflammatory and modulatory cytokines such as IL-6, IFN-γ, IL-8, macrophage inflammatory protein-1ß (MIP1ß), NAP-2, interferon-γ inducing protein-10 (IP-10) and angiogenin, as well as growth factors such as mesoderm inducing factor (MIF), vascular endothelial growth factor (VEGF), leukemia inhibitory factor (LIF), osteoprotegerin, hepatic growth factor (HGF), PARC, FGF-4, FGF-9, IGFBP3 and IGFBP4, were all significantly increased when compared to control CSF.