Somatic mutation in the neonatal mouse.
Several mechanisms that diversify the adult immune repertoire, such as terminal deoxynucleotidyl transferase-dependent N region addition, are not available to the neonatal mouse. One important process that contributes to protective immunity in the adult is somatic mutation, which plays a major role in the generation of high affinity memory B cells. It is not clear whether B cells in the neonatal mouse can activate the somatic mutation machinery. To investigate this, we immunized neonates with poly(L-Tyr,L-Glu)-poly-D,L-Ala-poly-L-Lys complexed with methylated BSA, or (4-hydroxy-3-nitrophenyl)acetyl coupled to chicken gamma-globulin. Eight to fourteen days after priming, V(D)J rearrangements of known V(H) genes (V(H)SM7 family) were screened for mutations using a temperature-melt hybridization assay and oligonucleotide probes specific for complementarity-determining regions I and II; possible mutations were confirmed by sequence analysis. More mutations per sequence were found in heavy chains from neonates immunized with (4-hydroxy-3-nitrophenyl)acetyl coupled to chicken gamma-globulin than in those from neonates immunized with poly(L-Tyr,L-Glu)-poly-D,L-Ala-poly-L-Lys complexed with methylated BSA. Mutations were found in heavy chains lacking N regions, suggesting that B cells of the putative fetal lineage can somatically mutate and diversify an initially limited repertoire. Since neonates immunized as early as 1 or 2 days after birth had mutations, the somatic mutation machinery can be activated soon after birth, suggesting that early vaccination should result in affinity maturation and protective immunity in the neonate.
Giorgetti
C A
CA
Brandeis University, Rosenstiel Research Center, Waltham, MA 02454, USA.
Press
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JL
D000818:Animals; D000831:Animals, Newborn / Q000235:genetics / Q000276:immunology*; D001483:Base Sequence; D002645:Chickens; D005260:Female; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D005803:Genes, Immunoglobulin; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000276:immunology; D009154:Mutation / Q000276:immunology*; D009596:Nitrophenols / Q000276:immunology; D010455:Peptides / Q000276:immunology; D010648:Phenylacetates; D012710:Serum Albumin, Bovine / Q000276:immunology; D005719:gamma-Globulins / Q000276:immunology
D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D009596:Nitrophenols; D010455:Peptides; D010648:Phenylacetates; D005719:gamma-Globulins; C026242:4-hydroxy-5-nitrophenyl acetic acid; D012710:Serum Albumin, Bovine; C021759:(T,G)-A-L