Phenotypic and Functional Analysis of Immune Cell Subsets in Pediatric-onset Multiple Sclerosis (MS): Towards Definition of Earliest Disease Mechanisms (P2.236)

OBJECTIVE: To characterize peripheral immune abnormalities in the earliest stages of MS. BACKGROUND: Substantial efforts have been invested to implicate distinct immune-cell subsets in MS pathophysiology. Though a number of aberrant immune-profiles or responses have been reported in adult-onset MS studies, an ongoing challenge has been to distinguish abnormalities that may develop as a consequence of established disease, from those directly involved in the CNS inflammatory injury of MS. Studying acquired pediatric-onset demyelination offers a unique window into early disease mechanisms given the narrower window between biological- and clinical-disease onset. METHODS: We developed 17 multiparametric flow-cytometry panels capturing both phenotypic and functional response-profiles of multiple immune cell (T and B-lymphocyte, myeloid, NK cell) subsets of putative interest, within both resting and activated peripheral-blood mononuclear cells (PBMC). Assay development included adaptation and validation for use with cryopreserved PBMC obtained using our strict standard operating procedures. We applied the flow-cytometry panels to cryopreserved PBMC obtained from children at time of their initial presentation with acquired demyelinating syndromes (ADS), as part of our prospective Canadian Pediatric Demyelinating Disease Study. Results were compared between children who, in prospective follow-up, were ascertained to have either MS (ADS-MS) or monophasic ADS (ADS-Mono). PBMC from age- and sex-matched healthy controls (HC) were analysed in parallel. RESULTS: A sequential cohort of 21 children examined to date demonstrates that, compared to both HC children and children with ADS-Mono, children with MS harbour significantly higher proportions of circulating CD4+CCR2+CCR5+ T cells (p = 0.0341) and CD8+CD161high mucosal associated invariant T (MAIT) cells (p = 0.0211). These two T-cell subsets were also the highest producers of both IL-17 (p = 0.0186) and IFNγ (p = 0.0043). CONCLUSION: Our findings selectively implicate CD4+CCR2+CCR5+ and CD8+CD161high MAIT T cell subsests in early pediatric-onset MS pathophysiology, but not in pediatric monophasic CNS inflammatory conditions. Disclosure: Dr. Nyirenda has nothing to disclose. Dr. Li has nothing to disclose. Dr. Moore has nothing to disclose. Dr. Rozenberg has nothing to disclose. Dr. Rezk has nothing to disclose. Dr. Johnson has nothing to disclose. Dr. Sadovnick has received personal compensation for activities with Biogen Idec, Merck Serono, Teva Neuroscience, and Bayer Pharmaceuticals Corp. Dr. Arnold has received personal compensation for activities with Acorda Therapeutics, Bayer Pharmaceuticals Corporation, Biogen Idec, Coronado Biosciences, EMD Serono, Genentech Inc., Genzyme Corporation, GlaxoSmithKline Inc., MedImmune, NeuroRx Research. Dr. Arnold has received research support from Bayer Pharmaceuticals Corporation. Dr. Marrie has received research support from the Canadian Institutes of Health Research, Multiple Sclerosis Society of Canada, Consortium of MS Centers, and Sanofi-Aventis Pharmaceuticals, Inc. Dr. Banwell has received personal compensation in an editorial capacity for Multiple Sclerosis and Related Disorders. Dr. Banwell9s institution has received research support from the Multiple Sclerosis Society of Canada, the Canadian Multiple Sclerosis Scientific Research Foundation, and Canadian Institute of Health Research. Dr. Bar-Or has received personal compensation for activities with Amplimmune, Aventis, Bayhill Therapeutics, Berlex/Bayer, Biogen Idec, BioMS, Diogenix, Eli Lilly & Company, EMD Serono, Genentech, Inc., Genzyme, GlaxoSmithKline, Inc., Guthy-Jackson/GGF, Medimmune, Mitsubishi Pharma, Novartis, Ono Pharma, Receptos, Roche, Sanofi-Aventis Pharmaceuticals, Inc., Teva Neuroscience, and Wyeth Pharmaceuticals. Dr. Bar-Or has received research support from Amplimmune, EMD Serono, and Novartis.