title: Bystander activation of CD8+ T lymphocytes during experimental mycobacterial infection.
abstract: Infection of C57BL/6 mice with Mycobacterium avium leads to the activation of both CD4+ and CD8+ gamma interferon (IFN-gamma)-producing T cells, although the CD8+ cells play no role in protection against infection. Using transfer of different lines of transgenic T cells with T-cell receptors (TCRs) which recognize irrelevant antigens, we show here that transferred CD8+ T cells from two of the three lines were activated to the same degree as the host cells, suggesting that the majority of the IFN-gamma-producing CD8+ T cells of the host represented bystander activation. The third line, specific for the male HY antigen, showed no activation. Activation required the participation of the CD28 coreceptor on T cells and was unaffected by the removal of CD44(hi) (memory phenotype) T cells. The transferred CD8+ T cells proliferated in vivo, although this was not essential for IFN-gamma production. Taken together, these data are highly reminiscent of homeostatic proliferation of TCR transgenic T cells upon transfer to lymphopenic hosts, and suggest low-affinity stimulation through the TCR, possibly by self peptides. The findings are discussed in relation to homeostatic proliferation and their significance in the possible induction of autoimmune disease.
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia.
authors.forename: Brad
authors.initials: B
authors.lastname: Gilbertson
authors.forename: Susie
authors.initials: S
authors.lastname: Germano
authors.forename: Pauline
authors.initials: P
authors.lastname: Steele
authors.forename: Steven
authors.initials: S
authors.lastname: Turner
authors.forename: Barbara
authors.initials: B
authors.lastname: Fazekas de St Groth
authors.forename: Christina
authors.initials: C
authors.lastname: Cheers
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D007371:Interferon-gamma / Q000096:biosynthesis; D019409:Interleukin-15 / Q000502:physiology; D015851:Interleukin-7 / Q000502:physiology; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D009162:Mycobacterium avium; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D014376:Tuberculosis / Q000276:immunology* / Q000662:veterinary
chemical_list: D019409:Interleukin-15; D015851:Interleukin-7; D011948:Receptors, Antigen, T-Cell; D007371:Interferon-gamma