Cytotoxic T cells infiltrating a glioma express an aberrant phenotype that is associated with decreased function and apoptosis.
In this study, we report on novel alterations found in rat intracranial (i.c.) tumor-infiltrating T lymphocytes (TIL) that are indicative of T cell defects and death. FACS analysis showed that the cytotoxic T cells (CTL) infiltrating rat T9.F gliomas were CD3epsilon+, alphabetaTCR+, CD8alpha+, but CD8beta-. These lymphocytes also stained positive for the B cell-specific marker, CD45RA, as well as Annexin-V, signifying apoptotic changes. Functional and biochemical analyses were performed to assess whether the aberrant phenotype was linked to other defects. When CD8alpha+ TIL were purified and stimulated in vitro, their proliferative capacity was markedly diminished in comparison with CD3+CD8alpha+CD8beta+ T cells isolated from the spleens of naive, non tumor-bearing rats. Furthermore, the mean fluorescence intensity of surface CD3epsilon was dramatically reduced in the CD3+CD8alpha+CD8beta- TIL population as compared with CD3-CD8alpha+CD8beta+ TIL from the same tumor-bearing animal. Biochemical studies revealed that the expression of TCRzeta and LAT were reduced in lysates generated from CD8alpha-purified TIL with respect to CD8alpha-purified T cells from naive spleen. We believe that these degenerative changes are reflective of chronic T cell receptor ligation, because in vitro culture of rat splenocytes or purified T cells with ConA or anti-CD3 mAb induced the same alterations. In vitro, the downregulation of CD8beta could be inhibited by the caspase inhibitor, z-VAD. These results suggest that the aberrant CTL phenotype found in the TIL of glioma-bearing rats may be novel signals for their impending death and degenerating anti-tumor immune function.
Prins
R M
RM
Department of Anatomy, Virginia Commonwealth University/Medical College of Virginia School of Medicine, Richmond 23298-0709, USA. prinsr@cshs.org
Graf
M R
MR
Merchant
R E
RE
D000818:Animals; D017304:Annexin A5 / Q000096:biosynthesis; D017209:Apoptosis / Q000276:immunology*; D001932:Brain Neoplasms / Q000276:immunology*; D016827:CD8 Antigens / Q000096:biosynthesis; D015536:Down-Regulation / Q000276:immunology; D005260:Female; D005910:Glioma / Q000276:immunology*; D016130:Immunophenotyping; D017493:Leukocyte Common Antigens / Q000096:biosynthesis; D008213:Lymphocyte Activation / Q000276:immunology; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology* / Q000378:metabolism / Q000502:physiology; D051381:Rats; D011916:Rats, Inbred F344; D015398:Signal Transduction / Q000276:immunology; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism / Q000502:physiology
D017304:Annexin A5; D016827:CD8 Antigens; D017493:Leukocyte Common Antigens