Depletion of functionally active CD20+ T cells by rituximab treatment.
OBJECTIVE
Rituximab is a therapeutic anti-CD20 antibody used for in vivo depletion of B cells in proliferative and autoimmune diseases. However, the mechanisms of action are not fully understood, since not all of the therapy-mediated effects can be explained by the depletion of antibody-secreting cells. In addition to B cells, there is also a small population of T cells coexpressing CD20 in all individuals. This study was conducted to examine the phenotype and function of CD3+CD20+ T cells in patients with rheumatoid arthritis (RA) and healthy controls.


METHODS
The phenotype and apoptosis of peripheral blood mononuclear cells from healthy donors and RA patients were examined by 4-color fluorescence-activated cell sorting analyses. Cytokine production was determined by intracellular staining and measurement of cytokines in the supernatants. Proliferation of sorted T cell populations was analyzed using 3H-thymidine uptake assays.


RESULTS
In healthy individuals, 0.1-6.8% of peripheral blood T cells (mean 1.6%; n=142) coexpressed CD20, which was not significantly different from that in the peripheral blood of RA patients, in whom 0.4-2.6% of T cells (mean 1.2%; n=27) were CD20+. During rituximab therapy, the CD20+ T cells along with the B cells were eliminated from the RA peripheral blood. Among the CD20+ T cells, 45% coexpressed CD8 and 55% coexpressed CD4. Polyclonal CD3+CD20+ cells were functionally characterized by constitutive cytokine production (i.e., interleukin-1beta and tumor necrosis factor alpha), a low proliferative capacity, a high activation state, and enhanced susceptibility to apoptosis.


CONCLUSIONS
These findings suggest that CD20+ T cells represent a terminally differentiated cell type with immune-regulatory and proinflammatory capacities. Depletion of CD20+ T cells may be an additional mechanism by which anti-CD20 therapy functions in patients with RA.
Wilk
Esther
E
Clinic for Immunology and Rheumatology, Hannover Medical School, Hannover, Germany.
Witte
Torsten
T
Marquardt
Nicole
N
Horvath
Tibor
T
Kalippke
Katy
K
Scholz
Kirsten
K
Wilke
Nadine
N
Schmidt
Reinhold E
RE
Jacobs
Roland
R
D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D015415:Biomarkers / Q000378:metabolism; D017252:CD3 Complex / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D016207:Cytokines / Q000378:metabolism; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D007155:Immunologic Factors / Q000494:pharmacology*; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D010641:Phenotype; D000069283:Rituximab; D016176:T-Lymphocyte Subsets / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000473:pathology
D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D015415:Biomarkers; D017252:CD3 Complex; D016207:Cytokines; D007155:Immunologic Factors; D000069283:Rituximab