CD4+CD25 high regulatory T-cells of patients with Multiple Sclerosis have a reduced suppressive effect on proliferation and cytokine secretion of responder T-cells

Background: Myelin specific autoreactive T-lymphocytes are present in the peripheral T cell repertoire in patients with multiple sclerosis (MS) as well as in healthy individuals. A fundamental dysregulation of the immune system seems to exist in MS patients, the exact mechansims underlying this occurrence are as yet undefined. A subset of T-lymphocytes, CD4+CD25high regulatory T cells (Treg), are able to suppress autoimmune responses and protect rodents from organ-specific autoimmune disease. Therefore a dysfunction of Treg and consecutively the failure to maintain peripheral immune tolerance could be an important event in the pathomechanism of MS. Thus, the aim of this study was to directly examine the number, phenotype and function of Treg isolated from peripheral blood of MS patients.

Methods: 33 patients with relapsing remitting MS (mean age 32 y) and 33 age matched healthy controls were included in the study. Patients had an acute relapse and were treatment nave. Median disease duration was 15 month. CD 4+ T cells were enriched from peripheral blood monocytes by a CD4+ isolation kit (Dynal). Treg and CD4+CD25- T effector cells (Teff) were separated from the CD4 fraction with anti-CD25 Dynalbeads. For in vitro proliferation assays Teff and Treg were stimulated alone or in co-culture either polyclonally with soluble anti-CD3/CD28 mAbs or with the MS candidate autoantigen MOG (myelin oligodendrocyte glycoprotein). Proliferative immune responses were determined by measuring 3(H)thymidine incorporation, secretion of cytokines IL-2,-4,-5,-6,-8,-10,-13, TNF alpha, INF gamma, GM-CSF and MIP-1 beta in cell culture supernatants was quantified using a BioPlex Array System.

Results/Conclusion: As revealed by FACS analysis the number and surface expression profile of Treg and Teff were not altered in MS patients. Freshly isolated Teff as well as Treg did not differ in cytokine release and proliferation rate between the two study cohorts. This was also evident upon in vitro stimulation with anti-CD3/CD28 or with MOG. However, under co-culture conditions Treg derived from MS patients showed a significant impaired ability to suppress both proliferation and cytokine secretion of Teff, whereas Treg isolated from healthy individuals showed a strong inhibitory effect in all conditions examined. Thus, our data suggests that the impaired function of Treg may be involed in the pathomechanisms of MS.

The study was supported by Gemeinnützige Hertie-Stiftung (1.319.110/01/11)