Involvement of inducible costimulator in the exaggerated memory B cell and plasma cell generation in systemic lupus erythematosus.
OBJECTIVE
In systemic lupus erythematosus (SLE), the increased generation of memory B cells and plasma cells leads to autoimmune hypergammaglobulinemia and destructive immunoglobulin deposits in the kidneys. We undertook this study to determine the biologic mechanism driving this overactivation of the B cell compartment, which is the central issue in SLE.


METHODS
We used flow cytometry to analyze expression of the T cell-specific inducible costimulator (ICOS) and its ligand (ICOS-L) on B cells obtained from the peripheral blood of SLE patients. We correlated ICOS-L expression with the differentiation status of the B cells using a large panel of surface antigens. In addition, SLE kidneys were analyzed by immunohistology.


RESULTS
We found an increased expression of ICOS on CD4+ as well as CD8+ T cells in SLE. At the same time, we documented a down-regulation of ICOS-L on a high proportion of peripheral blood memory B cells. Based on in vitro experiments, we inferred that this ICOS-L down-regulation on B cells was a signature of recent interaction with ICOS+ T cells in vivo. In the kidneys of SLE patients, we found clusters of B cells and plasma cells in close contact with ICOS+ T cells.


CONCLUSIONS
Detailed analysis of B cells with down-regulated ICOS-L suggests that ICOS is one of the forces driving the formation of memory B cells and plasma cells in SLE. Furthermore, our identification of plasma cells in areas of T cell-B cell interaction in kidneys suggests that components of a T cell-driven B cell activation process may take place in peripheral tissues in SLE.
Robert Koch Institute, Berlin, Germany.
Andreas
A
Hutloff
Kerstin
K
Büchner
Karin
K
Reiter
Hans J
HJ
Baelde
Marcus
M
Odendahl
Annett
A
Jacobi
Thomas
T
Dörner
Richard A
RA
Kroczek
D000293:Adolescent; D000328:Adult; D000368:Aged; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis / Q000502:physiology*; D001402:B-Lymphocytes / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007156:Immunologic Memory / Q000502:physiology*; D060945:Inducible T-Cell Co-Stimulator Ligand; D060889:Inducible T-Cell Co-Stimulator Protein; D007668:Kidney / Q000276:immunology; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D010950:Plasma Cells / Q000276:immunology*; D011506:Proteins / Q000032:analysis; D018344:T-Lymphocytopenia, Idiopathic CD4-Positive / Q000276:immunology
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; C556692:ICOS protein, human; C498514:ICOSLG protein, human; D060945:Inducible T-Cell Co-Stimulator Ligand; D060889:Inducible T-Cell Co-Stimulator Protein; D011506:Proteins