Rearrangement and Junctional-Site Sequence Analyses of T-Cell Receptor Gamma Genes in Intestinal Intraepithelial Lymphocytes from Murine Athymic Chimeras

Abstract

The molecular organization of rearranged T-cell receptor (TCR) γ genes in intraepithelial lymphocytes (IEL) was studied in athymic radiation chimeras and was compared with the organization of γ gene rearrangements in IEL from thymus-bearing animals by polymerase chain reaction and by sequence analyses of DNA spanning the junction of the variable (V) and joining (J) genes. In both thymus-bearing mice and athymic chimeras, IEL V-J γ-gene rearrangements occurred for Vγ1.2, Vγ2, and Vγ5 but not for Vγ3 or Vγ4. Sequence analyses of cloned V-J polymerase chain reaction-amplified products indicated that in both thymus-bearing mice and athymic chimeras, rearrangement of Vγ1.2 and Vγ5 resulted in in-frame as well as out-of-frame genes, whereas nearly all Vγ2 rearrangements were out of frame from either type of animal. V-segment nucleotide removal occurred in most Vγ1.2, Vγ2, and Vγ5 rearrangements; J-segment nucleotide removal was common in Vγ1.2 but not in Vγ2 or Vγ5 rearrangements. N-segment nucleotide insertions were present in Vγ1.2, Vγ2, and Vγ5 IEL rearrangements in both thymus-bearing mice and athymic chimeras, resulting in a predominant in-frame sequence for Vγ5 and a predominant out-of-frame sequence for Vγ2 genes. These findings demonstrate that (i) TCR γ-gene rearrangement occurs extrathymically in IEL, (ii) rearrangements of TCR y genes involve the same V genes regardless of thymus influence; and (iii) the thymus does not determine the degree to which functional or nonfunctional rearrangements occur in IEL.