B cell selection and affinity maturation during an antibody response in the mouse with limited B cell diversity.
The quasi-monoclonal mouse has limited B cell diversity, whose major (approximately 80%) B cell Ag receptors are comprised of the knockin V(H) 17.2.25 (V(H)T)-encoded H chain and the lambda1 or lambda2 L chain, thereby being specific for 4-hydroxy-3-nitrophenylacetyl. The p-nitrophenylacetyl (pNP) was found to be a low affinity analog of nitrophenylacetyl. We examined affinity maturation of anti-pNP IgG by analyzing mAbs obtained from quasi-monoclonal mice that were immunized with this low affinity Ag. The results are: 1) Although V(H)T/lambda1 and V(H)T/lambda2 IgM were equally produced, V(H)T/lambda2 IgG almost exclusively underwent affinity maturation toward pNP. 2) A common mutation in complementarity-determining region 3 of V(H)T (T313A) mainly contributed to generating the specificity for pNP. 3) Because mutated V(H)T-encoded gamma-chains could form lambda1-bearing IgG in Chinese hamster ovary cells, apparent absence of V(H)T/lambda1 anti-pNP IgG may not be due to the incompatibility between the gamma-chains and the lambda1-chain, but may be explained by the fact that V(H)T/lambda1 B cells showed 50- to 100-fold lower affinity for pNP than V(H)T/lambda2 B cells. 4) Interestingly, a pNP-specific IgM mAb that shared common mutations including T313A with high affinity anti-pNP IgG was isolated, suggesting that a part of hypermutation coupled with positive selection can occur before isotype switching. Thus, even weak B cell receptor engagement can elicit an IgM response, whereas only B cells that received signals stronger than a threshold may be committed to an affinity maturation process.
Kanayama
Naoki
N
Department of Biotechnology, Faculty of Engineering, Okayama University, Tsushima-Naka, Okayama, Japan.
Kimoto
Takafumi
T
Todo
Kagefumi
K
Nishikawa
Yumiko
Y
Hikida
Masaki
M
Magari
Masaki
M
Cascalho
Marilia
M
Ohmori
Hitoshi
H
D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000235:genetics; D000915:Antibody Affinity / Q000235:genetics; D000916:Antibody Diversity / Q000235:genetics; D000918:Antibody Specificity / Q000235:genetics; D016175:B-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D001483:Base Sequence; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D002999:Clone Cells; D018985:Epitopes, B-Lymphocyte / Q000276:immunology; D006241:Haptens / Q000276:immunology / Q000378:metabolism; D007074:Immunoglobulin G / Q000096:biosynthesis; D007143:Immunoglobulin Heavy Chains / Q000096:biosynthesis / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000096:biosynthesis* / Q000378:metabolism; D007146:Immunoglobulin lambda-Chains / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009596:Nitrophenols / Q000276:immunology / Q000378:metabolism; D010648:Phenylacetates; D017354:Point Mutation; D011947:Receptors, Antigen, B-Cell / Q000502:physiology
D000911:Antibodies, Monoclonal; D018985:Epitopes, B-Lymphocyte; D006241:Haptens; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D007146:Immunoglobulin lambda-Chains; D009596:Nitrophenols; D010648:Phenylacetates; D011947:Receptors, Antigen, B-Cell; C026242:4-hydroxy-5-nitrophenyl acetic acid