Germline transcription and expression of Tcrb-V8 genes in peripheral mouse lymphoid tissues

Germline transcription of the Tcrb-V8.2 gene has been recently shown to occur in a lymphoid precursor cell line and to result in weak expression of an aberrant T-cell receptor (Tcr) beta chain on the cell surface. An investigation into the expression of a similar Tcr structure in normal lymphoid sites has involved antibody staining and sorting to identify a minor subset of Tcr-Vbeta+ Cbeta- cells in mesenteric lymph node and thymus. These cells have been analyzed by reverse transcriptase-polymerase chain reaction for the presence of transcripts encoded by bV8 genes in rearranged vs germline configuration in subsets of cells sorted on the basis of Tcrb-V8 and Tcrb-C gene expression. Germline transcripts were found in the Tcr-Vbeta- Cbeta- subset of cells in bone marrow, thymus, and mesenteric lymph node. They were also found to be present in the Tcr-Vbeta8(+) Cbeta+ subset of cells in thymus and mesenteric lymph node. Cells in the Tcr-Vbeta8(+) Cbeta- subset of mesenteric lymph node contained germline but no rearranged bV8 transcripts. The same thymus subset expressed high levels of both rearranged and germline bV8 transcripts. The presence of germline bV8 transcripts in Tcr-alphabeta- cells in bone marrow and mesenteric lymph node suggests that germline Tcrb-V8 gene transcription is unrelated to the differentiation of mature T cells. The possible function and significance of the expression of a truncated Tcr beta chain is discussed.