Multi-centre validation of a flow cytometry method to identify optimal responders to interferon-beta in multiple sclerosis.

BACKGROUND AND OBJECTIVES: Percentages of blood CD19+CD5+ B cells and CD8+perforin+ T lymphocytes can predict response to Interferon (IFN)-beta treatment in relapsing-remitting multiple sclerosis (RRMS) patients. We aimed to standardize their detection in a multicenter study, prior to their implementation in clinical practice. METHODS: Fourteen hospitals participated in the study. A reference centre was established for comparison studies. Peripheral blood cells of 105 untreated RRMS patients were studied. Every sample was analyzed in duplicate in the participating centre and in the reference one by flow cytometry. When needed, participating centres corrected fluorescence compensations and negative cut-off position following reference centre suggestions. Concordance between results obtained by participating centres and by reference one was evaluated by intraclass correlation coefficients (ICC) and Spearman correlation test. Centre performance was measured by using z-scores values. RESULTS: After results review and corrective actions implementation, overall ICC was 0.86 (CI: 0.81-0.91) for CD19+CD5+ B cell and 0.89 (CI: 0.85-0.93) for CD8+ perforin+ T cell quantification; Spearman r was 0.92 (0.89-0.95; p <0.0001) and 0.92 (0.88-0.95; p <0.0001) respectively. All centres obtained z-scores≤0.5 for both biomarkers. CONCLUSION: Homogenous percentages of CD19+CD5+ B cells and CD8 perforin+ T lymphocytes can be obtained if suitable compensation values and negative cut-off are pre-established.

Relapsing-Remitting Multiple Sclerosis Is Characterized by a T Follicular Cell Pro-Inflammatory Shift, Reverted by Dimethyl Fumarate Treatment.

Multiple sclerosis (MS) is considered a T cell-mediated autoimmune disease, although several evidences also demonstrate a B cell involvement in its etiology. Follicular T helper (Tfh) cells, a CXCR5-expressing CD4+ T cell subpopulation, are essential in the regulation of B cell differentiation and maintenance of humoral immunity. Alterations in circulating (c)Tfh distribution and/or function have been associated with autoimmune diseases including MS. Dimethyl fumarate (DMF) is a recently approved first-line treatment for relapsing-remitting MS (RRMS) patients whose mechanism of action is not completely understood. The aim of our study was to compare cTfh subpopulations between RRMS patients and healthy subjects and evaluate the impact of DMF treatment on these subpopulations, relating them to changes in B cells and humoral response. We analyzed, by flow cytometry, the distribution of cTfh1 (CXCR3+CCR6-), cTfh2 (CXCR3-CCR6-), cTfh17 (CXCR3-CCR6+), and the recently described cTfh17.1 (CXCR3+CCR6+) subpopulations of CD4+ Tfh (CD45RA-CXCR5+) cells in a cohort of 29 untreated RRMS compared to healthy subjects. CD4+ non-follicular T helper (Th) cells (CD45RA-CXCR5-) were also studied. We also evaluated the effect of DMF treatment on these subpopulations after 6 and 12 months treatment. Untreated RRMS patients presented higher percentages of cTfh17.1 cells and lower percentages of cTfh2 cells consistent with a pro-inflammatory bias compared to healthy subjects. DMF treatment induced a progressive increase in cTfh2 cells, accompanied by a decrease in cTfh1 and the pathogenic cTfh17.1 cells. A similar decrease of non-follicular Th1 and Th17.1 cells in addition to an increase in the anti-inflammatory Th2 subpopulation were also detected upon DMF treatment, accompanied by an increase in naïve B cells and a decrease in switched memory B cells and serum levels of IgA, IgG2, and IgG3. Interestingly, this effect was not observed in three patients in whom DMF had to be discontinued due to an absence of clinical response. Our results demonstrate a possibly pathogenic cTfh pro-inflammatory profile in RRMS patients, defined by high cTfh17.1 and low cTfh2 subpopulations that is reverted by DMF treatment. Monitoring cTfh subsets during treatment may become a biological marker of DMF effectiveness.

Rheumatoid factor interference in a tacrolimus immunoassay.

Recently, there has been an interest in the use of tacrolimus for the treatment of rheumatoid arthritis (RA). The role of rheumatoid factor (RF) as a cause of immunoassay interferences is well known. This study is the first to investigate the susceptibility of a tacrolimus immunoassay to interference by RF. Tacrolimus apparent concentrations were determined using the antibody conjugated magnetic immunoassay (ACMIA) run on the Dimension RxL Immunoassay System in 100 randomly selected samples previously submitted for routine diagnostic or monitoring of RA in patients not receiving tacrolimus. Fifty of them had an RF concentration exceeding 100 IU/L and 50 had an RF concentration below 20 IU/L. Samples with tacrolimus apparent whole-blood concentrations above 2.3 ng/mL (limit of quantification of the ACMIA assay alleged by the vendor) were considered as potential false positives. No positive tacrolimus result was found among the 50 samples with serum RF < 20 IU/mL. Among the 50 selected samples from patients with RF > 100 IU/mL (RF range 110-2650 IU/mL), 2 were positive for tacrolimus with ACMIA. In both cases, the pretreatment of these samples with an immunoglobulin blocking agent reduced the apparent tacrolimus concentrations to below the limit of detection. This was confirmed using the alternative and reference tacrolimus assays, both of which reported results below their respective limits of detection. The measured human anti-mouse antibodies levels were found to be elevated. These results show that certain patients with positive RF can have false-positive tacrolimus results using the tacrolimus ACMIA-Flex immunoassay on a Dimension RXL analyzer, which was not the case with 2 other techniques. The interference with the tacrolimus ACMIA results was suppressed after preincubation with an immunoglobulin blocking reagent.