Association between peripheral blood immunological status and intrathecal inflammatory markers differentiate multiple sclerosis clinical phenotypes

Background The difference in the clinical course, response to therapy, and distribution of CNS inflammation in primary-progressive (PPMS) and relapsing-remitting multiple sclerosis (RRMS) suggests differences in the underlying immunological characteristics of the disease. We aimed to investigate differences in immunological profiles in relation to intrathecal inflammation in different MS forms. Methods The peripheral blood (PB) proportions of CD4+and CD8+T-cells and CD19+B-cells were retrospectively compared with the markers of intrathecal immunoglobulin G (IgG) synthesis at diagnosis: IgG index, percentage of intrathecal IgG synthesis (IF IgG), the number of oligoclonal bands (OCB), depending on the blood-brain barrier (BBB) function, and antibody specific index to neurotrophic viruses (MRZH reaction). Results Thirty-six controls, 71 RRMS and 25 PPMS were enrolled. PPMS had higher percentage of CD4+T-cells compared to RRMS (P=0.043) and controls (P=0.003). The percentage of CD8+T-cells and CD19+B-cells, and respective absolute cell counts did not differ according to the MS phenotype. In RRMS with the dysfunctional BBB, the IgG index (r=0.642, P=0.012) correlated significantly with the CD19+B-cells while the CD4+T-cells inversely correlated with IF IgG (r=-0.574, P=0.039). Interestingly, in PPMS the number of OCB was positively associated with CD4+ (r=0.603, P=0.015) and negatively associated with CD8+T-cells (r=-0.554, P=0.033), while IF IgG negatively correlated with CD8+T-cells (r=-0.689, P=0.003), but only in the preserved BBB function. Conclusions The PB CD4+T-cells and B-cells were associated with the intrathecal inflammation in RRMS with BBB dysfunction while CD8+T-cells were involved in PPMS with CNS-compartmentalized inflammation.