Relaxed negative selection in germinal centers and impaired affinity maturation in bcl-xL transgenic mice.
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The role of apoptosis in affinity maturation was investigated by determining the affinity of (4-hydroxy-3-nitrophenyl)acetyl (NP)-specific antibody-forming cells (AFCs) and serum antibody in transgenic mice that overexpress a suppressor of apoptosis, Bcl-xL, in the B cell compartment. Although transgenic animals briefly expressed higher numbers of splenic AFCs after immunization, the bcl-xL transgene did not increase the number or size of germinal centers (GCs), alter the levels of serum antibody, or change the frequency of NP-specific, long-lived AFCs. Nonetheless, the bcl-xL transgene product, in addition to endogenous Bcl-xL, reduced apoptosis in GC B cells and resulted in the expansion of B lymphocytes bearing VDJ rearrangements that are usually rare in primary anti-NP responses. Long-lived AFCs bearing these noncanonical rearrangements were frequent in the bone marrow and secreted immunoglobulin G(1) antibodies with low affinity for NP. The abundance of noncanonical cells lowered the average affinity of long-lived AFCs and serum antibody, demonstrating that Bcl-xL and apoptosis influence clonal selection/maintenance for affinity maturation.
Bone Marrow Cells
Gene Rearrangement, B-Lymphocyte, Heavy Chain
Immunoglobulin Variable Region
Mice, Inbred C57BL
Molecular Sequence Data
Proto-Oncogene Proteins c-bcl-2
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James B. Duke Distinguished Professor of Immunology
1. Lymphocyte development and antigen-driven diversification of immunoglobulin and T cell antigen receptor genes. 2. The germinal center reaction and mechanisms for clonal selection and self - tolerance. The origins of autoimmunity. 3. Interaction of innate- and adaptive immunity and the role of inflammation in lymphoid organogenesis. 4. The role of secondary V(D)J gene rearrangment in lymphocyte development and malignancies. 5. Mathematical modeling of immune responses,