B lymphocyte recognition of cytochrome c: higher frequency of cells specific for self versus foreign antigen early in the immune response and V gene usage in the response to self antigen.
To study immunoglobulin gene usage in the antibody response of mice to the self antigen (Ag) mouse cytochrome c (cyt), B cell hybridomas were prepared from splenic B cells of immunized BALB/c mice prior to the onset of somatic mutation, i.e. 3 days after injecting ovalbumin (OVA)-primed mice with mouse cyt coupled to OVA. Monoclonal antibodies (mAb) from all of the seven primary hybridomas we obtained were sensitive to a single amino acid substitution from aspartic acid to glutamic acid at position 62 in mouse cyt. This is the specificity of the vast majority of B cells responding to mouse cyt as determined from assays of B cells activated in splenic fragment cultures. Six of the mAb derive from the 19.1.2 J558 VH gene which is also used in the response to alpha (1-->6) dextran and three of these mAb derive from the R9 V kappa gene, a member of the V kappa Ox-1 family. The other mAb derive from distinct, although similar, V kappa genes. Attempts to obtain hybridomas secreting primary (unmutated) mAb specific for cyt foreign to mice have been hampered by the much lower frequency of B cells responding early to foreign cyt in comparison to the self Ag. This suggests that, contrary to expectation of tolerance mechanisms, in naive BALB/c mice B lymphocytes specific for a single epitope on self cyt are present in higher frequency than B lymphocytes specific for similar epitopes on foreign cyt. Possible explanations for this result include biased expression in the B cell repertoire of the particular combination of V genes encoding mouse cyt-specific mAb or to positive selection of developing B lymphocytes by endogenous Ag.
Minnerath
J M
JM
Department of Microbiology, University of Minnesota Medical School, Minneapolis, USA.
Mueller
C M
CM
Buron
S
S
Jemmerson
R
R
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000276:immunology; D000915:Antibody Affinity / Q000276:immunology; D000918:Antibody Specificity; D001324:Autoantigens / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D003574:Cytochrome c Group / Q000276:immunology*; D005260:Female; D006825:Hybridomas / Q000276:immunology; D007132:Immunoglobulin Isotypes / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000235:genetics* / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data
D000911:Antibodies, Monoclonal; D001324:Autoantigens; D003574:Cytochrome c Group; D007132:Immunoglobulin Isotypes; D007135:Immunoglobulin Variable Region