Development of the expressed Ig CDR-H3 repertoire is marked by focusing of constraints in length, amino acid use, and charge that are first established in early B cell progenitors.
To gain insight into the mechanisms that regulate the development of the H chain CDR3 (CDR-H3), we used the scheme of Hardy to sort mouse bone marrow B lineage cells into progenitor, immature, and mature B cell fractions, and then performed sequence analysis on V(H)7183-containing Cmu transcripts. The essential architecture of the CDR-H3 repertoire observed in the mature B cell fraction F was already established in the early pre-B cell fraction C. These architectural features include V(H) gene segment use preference, D(H) family usage, J(H) rank order, predicted structures of the CDR-H3 base and loop, and the amino acid composition and average hydrophobicity of the CDR-H3 loop. With development, the repertoire was focused by eliminating outliers to what appears to be a preferred repertoire in terms of length, amino acid composition, and average hydrophobicity. Unlike humans, the average length of CDR-H3 increased during development. The majority of this increase came from enhanced preservation of J(H) sequence. This was associated with an increase in the prevalence of tyrosine. With an accompanying increase in glycine, a shift in hydrophobicity was observed in the CDR-H3 loop from near neutral in fraction C (-0.08 +/- 0.03) to mild hydrophilic in fraction F (-0.17 +/- 0.02). Fundamental constraints on the sequence and structure of CDR-H3 are thus established before surface IgM expression.
Ivanov
Ivaylo I
II
Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Schelonka
Robert L
RL
Zhuang
Yingxin
Y
Gartland
G Larry
GL
Zemlin
Michael
M
Schroeder
Harry W
HW
D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D000916:Antibody Diversity / Q000235:genetics; D016175:B-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D001483:Base Sequence; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D022801:Complementarity Determining Regions / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D017124:Conserved Sequence; D005434:Flow Cytometry; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D005998:Glycine / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D007143:Immunoglobulin Heavy Chains / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D007133:Immunoglobulin Joining Region / Q000096:biosynthesis / Q000235:genetics; D007075:Immunoglobulin M / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D016364:Reading Frames / Q000235:genetics; D013234:Stem Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D014443:Tyrosine / Q000737:chemistry
D022801:Complementarity Determining Regions; D007143:Immunoglobulin Heavy Chains; D007133:Immunoglobulin Joining Region; D007075:Immunoglobulin M; D014443:Tyrosine; D005998:Glycine