Contributions
Abstract: P1192
Type: Poster Sessions
Abstract Category: Therapy - Immunomodulation/Immunosuppression
Objective: Analyzing the effect of alemtuzumab on circulating CD4+CD25hiFOXP3+ regulatory T cells (Treg) in patients with multiple sclerosis (MS)
Background: Treatment with alemtuzumab leads to depletion of circulating lymphocytes followed by asymmetric reconstitution of lymphocyte subsets. Contrary, a relative increase in Treg frequencies early after alemtuzumab therapy has been reported. Treg play an important role in controlling autoimmune responses and are functionally impaired in MS. Alemtuzumab predominantly affects CD45RO+ memory T cells and might differently affect naïve and memory Treg subsets. This is of importance since the loss of Treg suppressive properties in MS is associated with a dysbalanced composition of naïve and memory Treg subtypes which most likely results from an altered intrathymic Treg-neogenesis as we previously showed.
Design/Methods: 132 blood samples from 25 MS patients were taken shortly before and serially up to 24 months following alemtuzumab administration. We used flow cytometry for quantitation and phenotypical characterization of Treg. Treg function was determined by in vitro proliferation assays. Numbers of T-cell receptor (TCR) excision circles in Treg - a marker for thymic origin - were measured by real-time PCR. Clonal distribution of Treg was analyzed by CDR3-spectratyping.
Results: Shortly after alemtuzumab administration there was a massive increase in Treg frequencies. Post-depletional Tregs exhibited a CD45RO+ memory phenotype, a skewed TCR-repertoire and contained minimum TREC numbers. Re-increase in naïve Treg numbers, thymus markers, and TCR-variability started after six months without reaching baseline levels. Treg suppressive function constantly increased within one year when tested in cocultures with syngeneic effector T cells, but remained stable against allogeneic T cells from normal donors.
Conclusions: Our findings suggest that homoeostatic proliferation of alemtuzumab-resistant Treg clones contributes to the Treg expansion during the early phase following alemtuzumab administration. The enhanced inhibitory effect of Treg following alemtuzumab is possibly due to altered composition and reactivity of post-depletional effector T cells.
Disclosure: J. Haas: nothing to disclose. M. Korporal-Kuhnke: nothing to disclose. S. Jarius: nothing to disclose. B. Wildemann has served on a scientific advisory board for Novartis and Biogen Idec, has received funding for travel and speaker honoraria from Biogen Idec, Merck Serono, Teva Pharmaceutical Industries Ltd., and Genzyme-A Sanofi Company, and has received research support from Biogen Idec, Biotest Pharmaceuticals Corporation, Merck Serono, Novartis, and the BMBF.
Abstract: P1192
Type: Poster Sessions
Abstract Category: Therapy - Immunomodulation/Immunosuppression
Objective: Analyzing the effect of alemtuzumab on circulating CD4+CD25hiFOXP3+ regulatory T cells (Treg) in patients with multiple sclerosis (MS)
Background: Treatment with alemtuzumab leads to depletion of circulating lymphocytes followed by asymmetric reconstitution of lymphocyte subsets. Contrary, a relative increase in Treg frequencies early after alemtuzumab therapy has been reported. Treg play an important role in controlling autoimmune responses and are functionally impaired in MS. Alemtuzumab predominantly affects CD45RO+ memory T cells and might differently affect naïve and memory Treg subsets. This is of importance since the loss of Treg suppressive properties in MS is associated with a dysbalanced composition of naïve and memory Treg subtypes which most likely results from an altered intrathymic Treg-neogenesis as we previously showed.
Design/Methods: 132 blood samples from 25 MS patients were taken shortly before and serially up to 24 months following alemtuzumab administration. We used flow cytometry for quantitation and phenotypical characterization of Treg. Treg function was determined by in vitro proliferation assays. Numbers of T-cell receptor (TCR) excision circles in Treg - a marker for thymic origin - were measured by real-time PCR. Clonal distribution of Treg was analyzed by CDR3-spectratyping.
Results: Shortly after alemtuzumab administration there was a massive increase in Treg frequencies. Post-depletional Tregs exhibited a CD45RO+ memory phenotype, a skewed TCR-repertoire and contained minimum TREC numbers. Re-increase in naïve Treg numbers, thymus markers, and TCR-variability started after six months without reaching baseline levels. Treg suppressive function constantly increased within one year when tested in cocultures with syngeneic effector T cells, but remained stable against allogeneic T cells from normal donors.
Conclusions: Our findings suggest that homoeostatic proliferation of alemtuzumab-resistant Treg clones contributes to the Treg expansion during the early phase following alemtuzumab administration. The enhanced inhibitory effect of Treg following alemtuzumab is possibly due to altered composition and reactivity of post-depletional effector T cells.
Disclosure: J. Haas: nothing to disclose. M. Korporal-Kuhnke: nothing to disclose. S. Jarius: nothing to disclose. B. Wildemann has served on a scientific advisory board for Novartis and Biogen Idec, has received funding for travel and speaker honoraria from Biogen Idec, Merck Serono, Teva Pharmaceutical Industries Ltd., and Genzyme-A Sanofi Company, and has received research support from Biogen Idec, Biotest Pharmaceuticals Corporation, Merck Serono, Novartis, and the BMBF.