Functional and phenotypic analysis of thymic B cells: role in the induction of T cell negative selection.
The phenotype of mouse thymic B cells and their capacity to induce T cell negative selection in vitro were analyzed. Thymic B cells expressed B cell markers such as IgM, Fc gamma receptor, CD44, heat-stable antigen, LFA-1 and CD40. In addition, they were positive for the activation molecule CD69 and displayed high levels of B7-2. Although thymic B cells expressed CD5 on their surface, no CD5-specific mRNA was detected. Moreover, thymic B cells induced a stronger deletion of TCR-transgenic (TG) thymocytes than splenic B cells, which had low CD69 and B7-2 levels. Interestingly, CD40-activated splenic B cells up-regulated CD69 and B7-2 and acquired a capacity to induce T cell deletion comparable to that of thymic B cells. Moreover, thymic B cells from CD40-deficient mice displayed lower CD69 and B7-2 levels than control thymic B cells, and lower capacity to induce the deletion of TCR TG thymocytes. These results support the hypothesis that CD40-mediated activation of thymic B cells determines a high efficiency of antigen presentation, suggesting that within the thymus B cells may play an important role in the elimination of autoreactive thymocytes.
Ferrero
I
I
Department of Cell Biology, Faculty of Biology, Universidad Complutense, Madrid, Spain.
Anjuère
F
F
Martín
P
P
Martínez del Hoyo
G
G
Fraga
M L
ML
Wright
N
N
Varona
R
R
Márquez
G
G
Ardavín
C
C
D000818:Animals; D000956:Antigens, Viral / Q000276:immunology; D001402:B-Lymphocytes / Q000145:classification / Q000276:immunology*; D019013:CD40 Antigens / Q000235:genetics / Q000276:immunology; D018956:CD5 Antigens / Q000235:genetics; D016827:CD8 Antigens / Q000235:genetics; D005260:Female; D016130:Immunophenotyping; D008217:Lymphocytic choriomeningitis virus / Q000276:immunology; D008562:Membrane Glycoproteins / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology
D000956:Antigens, Viral; D019013:CD40 Antigens; D018956:CD5 Antigens; D016827:CD8 Antigens; D008562:Membrane Glycoproteins; C095378:Mtv-7 superantigen, Mouse mammary tumor virus; D016693:Receptors, Antigen, T-Cell, alpha-beta