Molecular characterization of hypoxanthine guanine phosphoribosyltransferase mutant T cells in human blood: The concept of surrogate selection for immunologically relevant cells

Clonality, trafficking, and molecular alterations among Hprt mutant T lymphocytes isolated from control mice versus mice treated with N‐ethyl‐N‐nitrosourea

“…Future demonstrations of a linkage between mutagenesis and T-cell clonal expansion will provide a potential mechanism to relate environmental exposures to risk for a variety of human diseases. To date, the HPRT mutation system has been an important tool in validating surrogate selection to investigate clinical disorders with immunological features (reviewed in Kaitz et al, 2022). However, assays for PIG-A mutations that do not require tissue culture have the potential to be more rapid and efficient as a surrogate selection tool for recognizing immunologically relevant cells in human patients with autoimmune disorders or cancer (Kaitz et al, 2022).…”

“…Sequencing with a constant beta (Cβ) gene primer that was internal to the PCR Cβ primer produced a sequence that began with $10 (Continues) It is striking that the Tcrb gene data for more than 300 T-cell isolates with wild-type Hprt revealed no instance of clonality in control mice, consistent with the vast repertoire (>10 8 ) of possible rearrangements (de Greef et al, 2020;Kaitz et al, 2022). This peak in MF in thymus was followed by a rapid decline to levels $sixto eight-fold greater than background at 4 and 6 weeks postexposure.…”

“…Hypoxanthine‐guanine phosphoribosyltransferase ( HPRT1 ) mutations in T lymphocytes (T‐cells) have been used for several decades as reporters of in vivo somatic mutations in humans, with increases in the frequency of these mutations serving as a useful marker for environmental genotoxic exposures (Albertini, 2001; Albertini et al, 1982, 2001; Morley et al, 1983; Tates & Lambert, 1999). Increases in HPRT mutant frequencies (MFs) also are found in clinical situations characterized by heightened immunological activity such as in autoimmune diseases and cancer (Abramson et al, 1999; Cannons et al, 1998; Kaitz et al, 2022; Lodge et al, 1994, 1996; van den Berg et al, 1995). In these cases, the MF elevations are thought to be due to increased T‐cell proliferation (Abramson et al, 1999), which can be both mutagenic and serve to amplify pre‐existing T‐cell mutants.…”

“…T‐cell clones can be identified by their T‐cell receptor (TCR) gene rearrangements that occur in the thymus during the ontogeny of these cells (Clark & Nicklas, 1996; Kaitz et al, 2022; Nicklas et al, 1986; O'Neill et al, 1994). T‐cells mature by rearranging germ‐line genetic regions to code for surface molecules (TCRs) capable of recognizing the universe of foreign (non‐self) molecules that may be encountered, while maintaining immunological self‐recognition and tolerance, during the life of the individual (Goodnow, 2007; Kaitz et al, 2022). The TCR beta locus ( Tcrb in the mouse) includes variable (V or Vβ), diversity (D or Dβ), joining/junctional (J or Jβ), and constant (C or Cβ) segments (Majumder et al, 2015).…”

“…The C segment is later joined by splicing at the RNA level. In a process termed V(D)J recombination (Kaitz et al, 2022), rearrangement of many different V segments with several J segments provides a wide range of antigen recognition that is augmented further by junctional diversity resulting from random addition of nucleotides by terminal deoxynucleotidyltransferase. The number of different TCRs that could, in principle, be produced by V(D)J gene rearrangement in the thymus is >10 8 (de Greef et al, 2020; Kaitz et al, 2022).…”