The in vivo generation of murine IgD-secreting cells is accompanied by deletion of the C mu gene and occasional deletion of the gene for the C delta 1 domain.
Mature, resting rodent, and primate B lymphocytes express two membrane Ig isotypes, IgM and IgD. Although membrane IgD production by these cells is regulated at a transcriptional level, and does not require deletion of the C mu gene, C mu has been deleted in all of the IgD-secreting tumor cells that have been studied. These IgD-secreting tumors, which include two mineral oil-induced plasmacytomas and three IgD-switch variants of an IgM-secreting hybridoma, might not, however, be representative of the rare IgD-secreting cells generated in response to an immune stimulus. A recent study of mice injected with a goat antibody to mouse IgD has demonstrated the generation of a relatively large secretory IgD response in these animals. We have now produced hybridomas by fusing spleen cells from these mice with a non-Ig-secreting plasmacytoma. Two of these hybridomas, KWD-1 and KWD-2, secrete IgD and express cell membrane IgD. Both of these hybridomas were found to have deleted the C mu gene. KWD-2 produces a delta-chain mRNA and a delta-chain protein similar in size to those previously reported for normal secreted mouse IgD; however, KWD-1 synthesizes a secretory delta-chain mRNA that is approximately 0.25 kb smaller than the KWD-2 secretory delta-chain mRNA and secretes IgD with a delta-chain that is approximately 21 kDa smaller than the secretory delta-chain of KWD-2. ELISA studies with epitope-defined anti-delta mAb indicate that KWD-2 has both delta Fc (C delta 3) [corrected] and delta Fd (C delta 1) [corrected] determinants, whereas KWD-1 has delta Fc but not delta Fd. These studies also demonstrate that the Ag-binding site of KWD-1 is not deleted because KWD-1 specifically binds goat IgG. Northern blot analyses with exon-specific probes indicate that while both KWD-1 and KWD-2 synthesize kappa-chain mRNA and delta-chain mRNA that includes the VH, C delta hinge, and C delta 3 exons, the C delta 1 exon is present only on the KWD-2 delta-chain mRNA. Southern blot analysis confirms that the C delta 1 exon has been deleted in KWD-1, but not KWD-2. We have previously noted that a secretory delta-chain mRNA that is similar in size to that produced by KWD-1 accounts for approximately 25% of the splenic secretory delta-chain mRNA produced by goat anti-mouse IgD antibody-injected mice.(ABSTRACT TRUNCATED AT 400 WORDS)
Mountz
J D
JD
Department of Medicine, University of Alabama, Birmingham 35294.
Mushinski
J F
JF
Owens
J D
JD
Finkelman
F D
FD
D000818:Animals; D015152:Blotting, Northern; D002872:Chromosome Deletion; D015342:DNA Probes; D000939:Epitopes; D015870:Gene Expression; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D005803:Genes, Immunoglobulin; D006825:Hybridomas; D007072:Immunoglobulin D / Q000378:metabolism*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007138:Immunoglobulin delta-Chains / Q000235:genetics* / Q000276:immunology; D007148:Immunoglobulin mu-Chains / Q000235:genetics*; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics; D011947:Receptors, Antigen, B-Cell / Q000235:genetics
D015342:DNA Probes; D000939:Epitopes; D007072:Immunoglobulin D; D007143:Immunoglobulin Heavy Chains; D007138:Immunoglobulin delta-Chains; D007148:Immunoglobulin mu-Chains; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011947:Receptors, Antigen, B-Cell