c-Fos induces apoptosis in germinal center B cells.
We examined the role of c-Fos in the differentiation of mature B cells into IgG-producing cells using transgenic mice carrying the c-fos gene under the control of the IFN-alpha/beta-inducible Mx promoter (Mx-c-fos) or the constitutive H-2Kb promoter (H2-c-fos). Splenic B cells from Mx-c-fos mice were cultured with LPS and rIL-4, and IgG1+ B cells were developed in the culture after day 3. When IFN-alpha/beta was added to the culture from day 2, development of IgG1+ B cells was perturbed, and the number of apoptotic cells increased within 24 h, suggesting that c-Fos induces apoptosis in Ig class-switching B cells. To confirm the effect of c-Fos on B cell differentiation in vivo, H2-c-fos mice were immunized with DNP-OVA. The mice produced primary IgM, but not IgG, anti-DNP Ab in serum and failed to generate germinal centers in spleen. The perturbation of germinal center formation in H2-c-fos mice was rescued by mating them with transgenic mice carrying the bcl-2 gene with the Ig promoter. However, primary IgG1 anti-DNP Ab production was still suppressed in doubly transgenic mice, suggesting that Bcl-2 can delay the time of c-Fos-induced apoptosis in Ig class-switching B cells but cannot rescue the death. Since c-Fos is induced in mature B cells reacted with Ags, and clonal deletion of self-reactive B cells in germinal centers is insensitive to Bcl-2, these results suggest that c-Fos plays a causal role in clonal deletion of germinal center B cells.
Inada
K
K
Department of Developmental Genetics, Chiba University Graduate School of Medicine, Japan.
Okada
S
S
Phuchareon
J
J
Hatano
M
M
Sugimoto
T
T
Moriya
H
H
Tokuhisa
T
T
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology / Q000473:pathology*; D005786:Gene Expression Regulation / Q000276:immunology; D016762:Genes, fos; D018858:Germinal Center / Q000276:immunology / Q000473:pathology*; D016898:Interferon-alpha / Q000235:genetics / Q000494:pharmacology; D016899:Interferon-beta / Q000235:genetics / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000276:immunology*
D016898:Interferon-alpha; D016760:Proto-Oncogene Proteins c-fos; D016899:Interferon-beta