title: The immune response to bacterial dextrans. III. Ontogenic development and strain distribution of specific clonal precursors.
abstract: The frequencies of B512 dextran (Dex)-specific B cell precursors were determined by limiting dilution analysis in a number of mouse strains originally described as "high responder", "low responder" and "nonresponder" to this antigen. No significant difference in the frequencies of Dex-specific precursors was found in C57BL/6, B10.BR, C3H/Tif, BALB/c and A/Sn adult mice. Together with the large intra-strain variability in the magnitude of anti-Dex PFC responses in vivo, these results established that differential reactivity in vivo cannot be ascribed to genetically controlled absence or wide variation in the frequency of Dex-specific immunocompetent precursors. A similar analysis of the Dex-specific precursor frequency was carried out in C57BL/6 mice between 1 week and 3 months of age. While no Dex-specific antibody response was detected in vivo before the age of 3 weeks, clonal precursor analysis revealed that the appearance of these specificities parallels the development of competent (IgM-producing) B lymphocyte clonal precursors, such that no significant difference in absolute frequencies of Dex-specific precursors could be observed among these age groups. This is interpreted to suggest that the late development of the Dex-specific antibody responses is regulatory rather than due to late rearrangement and activation of the appropriate V genes and a sequential expression of antibody specificities in ontogenic development.
mesh_terms: D000367:Age Factors; D000818:Animals; D000918:Antibody Specificity; D001402:B-Lymphocytes / Q000276:immunology*; D003911:Dextrans / Q000276:immunology*; D051379:Mice; D008815:Mice, Inbred Strains; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D013154:Spleen / Q000166:cytology
chemical_list: D003911:Dextrans; D011135:Polysaccharides, Bacterial