A hypothesis accounting for the paradoxical expression of the D gene segment in the BCR and the TCR.
The D gene segment expressed in both the TCR and the BCR has a challenging behavior that begs interpretation. It is incorporated in three reading frames in the rearranged transcription unit but is expressed in antigen-selected cells in a preferred frame. Why was it so important to waste 2/3 of newborn cells? The hypothesis is presented that the D region is framework playing a role in both the TCR and the BCR by determining whether a signal is transmitted to the cell upon interaction with a cognate ligand. This assumption operates in determining haplotype exclusion for the BCR and in regulating the signaling orientation for the TCR. Relevant data as well as a definitive experiment challenging the validity of this hypothesis, are discussed.
Conceptual Immunology Group, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA. cohn@salk.edu
Melvin
M
Cohn
D000818:Animals; D000916:Antibody Diversity / Q000235:genetics / Q000276:immunology; D005075:Biological Evolution; D015870:Gene Expression; D015332:Gene Rearrangement, alpha-Chain T-Cell Antigen Receptor; D015333:Gene Rearrangement, beta-Chain T-Cell Antigen Receptor; D019673:Genes, T-Cell Receptor alpha; D019674:Genes, T-Cell Receptor beta; D006801:Humans; D007136:Immunoglobulins / Q000235:genetics / Q000276:immunology; D016364:Reading Frames; D011947:Receptors, Antigen, B-Cell / Q000235:genetics* / Q000276:immunology; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics* / Q000276:immunology
D007136:Immunoglobulins; D011947:Receptors, Antigen, B-Cell; D016693:Receptors, Antigen, T-Cell, alpha-beta