Borrelia infection increases the frequency of PTCL arising from NKT cells. (A) Survival curves of p53^−/− mice infected with 5 × 10⁴ spirochetes (n = 29) or control medium (n = 39). (B) Bar graph shows the tumor spectra developed in infected and control p53^−/− mice. Other tumors include solid tumors and thymic lymphomas. (C) PTCLs are characterized by hepatosplenomegaly. Macroscopic images of livers and spleens from PTCL-bearing and healthy p53^−/− mice. (D) PTCLs show a significant increase in cells in liver and spleen. Data are mean ± SD. ****P < .0001, Mann-Whitney U test. (E) Hematoxylin phloxine saffron (HPS) staining of paraffin-embedded organ sections from healthy and PTCL-bearing p53^−/− mice. Arrows in middle panel indicate perivascular infiltrates of lymphoma cells. Arrow in the right panel denoted intrasinusoidal infiltrate of lymphoma cells. Scale bars, 200 µm (left and middle panels), 50 µm (right panels). (F) p53^−/− mice develop 2 types of PTCL. Flow cytometry analysis of PTCLs (gated on the CD3⁺ Thy1.2⁺ population) stained with αGalCer-loaded CD1d tetramers. Line graphs are representative of 2 PTCL types: CD1d tetramer–negative PTCL (gray shading; PTCL) and CD1d tetramer–positive PTCL (red shading; NKTL) (left panels). CD1d tetramer staining of all PTCLs compared with normal T and NKT cells (right panel). (G) Borrelia infection increases the frequency of NKTL. PTCL and NKTL frequency among all PTCLs in control and Borrelia-infected p53^−/− mice with significantly different PTCL spectra. *P < .02, χ² test.