Immunologic memory to phosphocholine keyhole limpet hemocyanin. Recurrent mutations in the lambda 1 light chain increase affinity for antigen.
Anti-phosphocholine (PC)-keyhole limpet hemacyanin hybridomas representative of a memory response that express the lambda 1 L chain isotype have a high reactivity to PC-protein. A common feature of these hybridomas possessing high affinity for PC-protein is the occurrence of somatic mutations resulting in replacement changes in three CDR2 positions of the lambda 1 L chain. The influence of each of these three positions on the Ag binding properties of these antibodies was examined by site-specific mutagenesis and expression of recombinant antibody molecules by transfected cells. Affinity measurements and fine specificity profile determinations demonstrated the importance of the three lambda 1 CDR2 positions in Ag binding. Compared to antibodies expressing germline lambda 1, including one with an additional junctional serine that is not encoded by V or J, those antibodies possessing critical changes in CDR2 would have a strong selective advantage based on affinity differences for Ag. Sequence analysis of a group of clonally related hybridomas expressing mutated lambda 1 genes allowed construction of a hypothetical genealogic tree that suggests selection based on changes in CDR2 of lambda 1 in the absence of H chain mutations. The results are consistent with stepwise acquisition of mutations and selection based on affinity constraints.
Brown
M
M
Department of Microbiology and Immunology, Oregon Health Sciences University, Portland 97201.
Stenzel-Poore
M
M
Stevens
S
S
Kondoleon
S K
SK
Ng
J
J
Bächinger
H P
HP
Rittenberg
M B
MB
D000818:Animals; D000915:Antibody Affinity; D001483:Base Sequence; D005803:Genes, Immunoglobulin; D006433:Hemocyanins / Q000276:immunology*; D006825:Hybridomas / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000502:physiology; D007146:Immunoglobulin lambda-Chains / Q000235:genetics / Q000502:physiology*; D007156:Immunologic Memory; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009154:Mutation; D010767:Phosphorylcholine / Q000276:immunology*
D007135:Immunoglobulin Variable Region; D007146:Immunoglobulin lambda-Chains; D010767:Phosphorylcholine; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin