The Immune System and the Plural Autisms: A Narrative Review

Plural autisms offer one important way of organising the massive heterogeneity that is currently included under the singular diagnostic label of autism spectrum disorder (ASD). Characterised exclusively by behavioural criteria related to social communication skills and restricted or repetitive patterns of symptoms, the observable diversity in presentations and developmental trajectories partially explains the lack of universally applicable biomarkers and answers about underlying biology. One particularly important area potentially pertinent to several manifestations of the plural autisms is a connection to the immune system, whether noted across differing patterns of immune functions or following immune challenge in the context of inflammatory processes exerting an effect on developmental processes and behaviour. Utilising a narrative review, we highlight various research analysing a role for immune functions in the context of the heterogeneous autisms stretching across under-, over- and autoimmune processes. Current evidence for immune system involvement in various autisms carries considerable limitations, and studies are often based on small sample sizes, focusing on selective clinical subgroups, and using case-based observations. Notwithstanding the available evidence, substantial and more detailed further studies are required in relation to immune-related screening, building also on the currently limited evidence on the potential usefulness of personalised immune-affecting interventions following appropriate screening and identification of pertinent immune-related issues.