title: Lack of coreceptor allows survival of chronically stimulated double-negative alpha/beta T cells: implications for autoimmunity.
abstract: Lymphoproliferative diseases are characterized by massive accumulation of CD4(-)CD8(-)B220(+) (double-negative [DN]) T cells in peripheral organs. Although evidence indicates these cells are derived from mature autoreactive alpha/beta T cells, the significance of coreceptor downregulation is not known. In this study, we examined the role CD4 coreceptor plays in the survival of repeatedly stimulated T cells. CD4(+/+) and CD4(-/-) T cells from AND T cell receptor (TCR) transgenic mice exhibited similar phenotypes after antigenic stimulation, but the CD4(-/-) T cells survived in much larger numbers than the CD4(+/+) cells upon primary and secondary major histocompatibility complex (MHC)/peptide stimulation. Enhanced survival of CD4(-/-) T cells was due to decreased apoptosis rather than enhanced proliferation. Similarly, circumvention of the CD4/MHC interaction by using a surrogate TCR ligand that does not engage CD4 led to significant enhancement of CD4(+/+) cells than when stimulated with MHC/peptide. Finally, we generated DN B220(+) T cells using an in vitro model system and showed they were more tolerant to chronic stimulation than CD4(+/+) cells. Together, these results indicate that coreceptor engagement controls expansion of normal T cells. In the absence of coreceptor, T cells survive chronic stimulation and express B220 as seen in autoimmune lymphoproliferative diseases.
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA. ahamad@jhmi.edu
authors.forename: A R
authors.initials: AR
authors.lastname: Hamad
authors.forename: A
authors.initials: A
authors.lastname: Srikrishnan
authors.forename: P
authors.initials: P
authors.lastname: Mirmonsef
authors.forename: C P
authors.initials: CP
authors.lastname: Broeren
authors.forename: C H
authors.initials: CH
authors.lastname: June
authors.forename: D
authors.initials: D
authors.lastname: Pardoll
authors.forename: J P
authors.initials: JP
authors.lastname: Schneck
mesh_terms: D000818:Animals; D017209:Apoptosis; D015551:Autoimmunity / Q000276:immunology*; D017252:CD3 Complex / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002470:Cell Survival; D017493:Leukocyte Common Antigens / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D008232:Lymphoproliferative Disorders / Q000209:etiology; D051379:Mice; D008822:Mice, Transgenic; D016693:Receptors, Antigen, T-Cell, alpha-beta; D011971:Receptors, Immunologic / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology*
chemical_list: D017252:CD3 Complex; D016693:Receptors, Antigen, T-Cell, alpha-beta; D011971:Receptors, Immunologic; D017493:Leukocyte Common Antigens