Effect of Fingolimod on Lymphocyte Subsets in Patients With Relapsing Multiple Sclerosis

Background and aim Multiple sclerosis (MS) is the most common chronic inflammatory demyelinating disease of the central nervous system (CNS). This study aims to evaluate the effect of fingolimod on T and B lymphocytes in relapsing-remitting multiple sclerosis (RRMS) patients. Method Multiple sclerosis patients were selected from patients who were scheduled to start medication at the outpatient clinic of Kocaeli University, Kocaeli, Turkey, between February 2019 and February 2022. Venous blood samples were obtained before starting medication from the patients who agreed to participate in the study and who were to start treatment, simultaneous clinical and neurologic examinations were performed and the Expanded Disability Status Scale (EDSS) was calculated. After the six-month treatment, venous blood samples were taken again. Lymphocyte subgroup analyses were performed in the flow cytometry laboratory. Results The study included 48 patients in the fingolimod group and 33 patients as controls. Flow cytometry analyses showed there was no significant difference between the two groups in the numbers and percentages of CD19+, CD20+, and CD22+ cells at baseline, while a significant decrease was observed in all of these parameters in the fingolimod group after the six-month treatment<i>.</i> Discussion Our findings support that the fingolimod treatment has significant effects on both lymphocyte counts and lymphocyte subgroup ratios. The results show the mechanism of action of fingolimod is unaccountable only through T lymphocytes, and it is effective in both B lymphocyte subgroups and T lymphocytes.