Terminal deoxynucleotidyl Transferase is required for an optimal response to the polysaccharide α-13 Dextran

摘要

An understanding of antibody responses to polysaccharides associated with pathogenic microorganisms is of importance for improving vaccine design, especially in neonates that respond poorly to these types of antigens. In this study, we have investigated the role of the lymphoid specific enzyme TdT in generating B cell clones responsive to α-1,3 Dextran (DEX). TdT is a DNA polymerase that plays a major role in generating diversity of lymphocyte antigen receptors during V(D)J recombination. In this study we show that the DEX-specific antibody response is lower and the dominant DEX-specific J558 idiotype (Id) is not detected in TdT−/− mice when compared to wild type BALB/c (WT) mice. Nucleotide sequencing of heavy chain CDR3s of DEX-specific plasmablasts, sorted post-immunization, showed that TdT−/− mice generate a lower frequency of the predominant adult molecularly-determined clone J558. Complementation of TdT expression in TdT−/− mice by early forced expression of the short splice variant of TdT restored WT proportions of J558 Id+ clones and also abrogated the development of the minor M104E Id+ clones. J558 Id V(D)J rearrangements are detected as early as 7 days after birth in IgM negative B cell precursors in the liver and spleen of WT and TdT transgenic mice but not in TdT−/− mice. These data show that TdT is essential for the generation of the predominant higher affinity DEX-responsive J558 clone.