RESUMEN
In a depleted lymphoid compartment, naive T cells begin a slow proliferation that is independent of cognate antigen yet requires recognition of major histocompatibility complex-bound self-peptides. We have followed the phenotypic and functional changes that occur when naive CD8(+) T cells undergo this type of expansion in a lymphopenic environment. Naive T cells undergoing homeostasis-driven proliferation convert to a phenotypic and functional state similar to that of memory T cells, yet distinct from antigen-activated effector T cells. Naive T cells dividing in a lymphopenic host upregulate CD44, CD122 (interleukin 2 receptor beta) and Ly6C expression, acquire the ability to rapidly secrete interferon gamma, and become cytotoxic effectors when stimulated with cognate antigen. The conversion of naive T cells to cells masquerading as memory cells in response to a homeostatic signal does not represent an irreversible differentiation. Once the cellularity of the lymphoid compartment is restored and the T cells cease their division, they regain the functional and phenotypic characteristics of naive T cells. Thus, homeostasis-driven proliferation provides a thymus-independent mechanism for restoration of the naive compartment after a loss of T cells.
Asunto(s)
Linfocitos T CD8-positivos/citología , Linfocitos T CD8-positivos/inmunología , Memoria Inmunológica , Traslado Adoptivo , Animales , Antígenos Ly/metabolismo , Diferenciación Celular , División Celular , Citotoxicidad Inmunológica , Citometría de Flujo , Genes RAG-1/genética , Genes RAG-1/fisiología , Homeostasis , Humanos , Receptores de Hialuranos/genética , Receptores de Hialuranos/metabolismo , Inmunofenotipificación , Interferón gamma/biosíntesis , Linfopenia , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Receptores de Antígenos de Linfocitos T/genética , Receptores de Antígenos de Linfocitos T/inmunología , Receptores de Antígenos de Linfocitos T/metabolismo , Receptores de Interleucina-2/genética , Receptores de Interleucina-2/metabolismoRESUMEN
The TCR V beta element is pivotal for superantigen recognition; however, not all T cells bearing a particular V beta element respond to an individual superantigen. Recent evidence has indicated that the TCR V alpha element also contributes to recognition of superantigen/MHC class II complexes. To determine whether the TCR beta-chain junctional regions influence recognition of a superantigen encoded by mouse mammary tumor virus (MMTV) proviral integrant Mtv-1, we have analyzed these regions in T cells that have survived superantigen-mediated negative selection in B10.BR-Mtv-1 mice. Our data indicate: 1) no TCR J beta skewing, 2) no difference in the length of the third complementarity-determining region (CDR3), and 3) no outstanding structural features that are shared among the junctional regions of the V beta 3+ T cells that escape thymic clonal elimination in superantigen-expressing mice. Several possible models for TCR engagement of viral superantigen/MHC class II complexes are discussed.
Asunto(s)
Supresión Clonal/genética , Receptores de Antígenos de Linfocitos T alfa-beta/química , Superantígenos/inmunología , Linfocitos T/inmunología , Secuencia de Aminoácidos , Animales , Presentación de Antígeno/genética , Composición de Base , Secuencia de Bases , Supresión Clonal/inmunología , Hibridomas , Virus del Tumor Mamario del Ratón/inmunología , Ratones , Ratones Endogámicos C3H , Ratones Endogámicos C57BL , Datos de Secuencia Molecular , Familia de Multigenes/inmunología , Provirus/inmunología , Receptores de Antígenos de Linfocitos T alfa-beta/genética , Relación Estructura-ActividadRESUMEN
Mouse mammary tumor viruses (MMTVs) encode superantigens that associate with major histocompatibility complex class II products on antigen-presenting cells and stimulate T cells in a V beta-specific manner. This T cell activation is critical for completion of the viral life cycle and vertical transmission to the next generation. To investigate the functional significance of extensive viral superantigen (Sag) glycosylation, we disrupted the six potential sites for N-linked carbohydrate addition in the Sag encoded by proviral integrant Mtv-1. Shifts in the apparent molecular mass of these mutant glycoproteins suggested that wild-type Mtv-1 Sag is glycosylated on four of its six sites. Intracellular and cell surface staining of the panel of mutants indicated that any decrease in glycosylation resulted in reduced levels of intracellular protein and undetectable surface expression, suggesting that decreased glycosylation leads to rapid Sag degradation and abates trafficking to the plasma membrane. Nevertheless, several mutants with intermediate levels of glycosylation expressed enough Sag on the B cell surface to potently stimulate reactive T cell hybrids. We show there is no specific site bearing N-linked glycosylation that is essential for activity, but at least one carbohydrate addition is necessary for effective B cell presentation of MMTV superantigens to T cells.
Asunto(s)
Presentación de Antígeno/inmunología , Antígenos Virales/inmunología , Virus del Tumor Mamario del Ratón/inmunología , Superantígenos/inmunología , Linfocitos T/inmunología , Secuencia de Aminoácidos , Animales , Antígenos Virales/genética , Sitios de Unión , Western Blotting , Línea Celular , Glicosilación , Virus del Tumor Mamario del Ratón/genética , Ratones , Datos de Secuencia Molecular , Mutación , ARN Mensajero , Superantígenos/genéticaRESUMEN
Chemokines are likely to play an important role in regulating the trafficking of developing T cells within the thymus. By using anti-CD3varepsilon treatment of recombinase-activating gene 2 (Rag2-/-) mice to mimic pre-TCR signaling and drive thymocyte development to the double positive stage, we have identified murine GPR-9-6 as a chemokine receptor whose expression is strongly induced following pre-TCR signaling. GPR-9-6 mRNA is present at high levels in the thymus, and by RT-PCR analysis its expression is induced as normal thymocytes undergo the double negative to double positive transition. Furthermore we show that TECK (thymus-expressed chemokine), a chemokine produced by thymic medullary dendritic cells, is a functional ligand for GPR-9-6. TECK specifically induces a calcium flux and chemotaxis of GPR-9-6-transfected cells. In addition, TECK stimulates the migration of normal double positive thymocytes, as well as Rag2-/- thymocytes following anti-CD3varepsilon treatment. Hence, GPR-9-6 has been designated as CC chemokine receptor 9 (CCR9). Our results suggest that TECK delivers signals through CCR9 important for the navigation of developing thymocytes.
Asunto(s)
Quimiocinas CC/metabolismo , Receptores de Antígenos de Linfocitos T/fisiología , Receptores de Quimiocina/biosíntesis , Transducción de Señal/inmunología , Células Madre/metabolismo , Timo/metabolismo , Regulación hacia Arriba/inmunología , Animales , Anticuerpos Monoclonales/farmacología , Calcio/metabolismo , Diferenciación Celular/genética , Diferenciación Celular/inmunología , Línea Celular , Movimiento Celular/inmunología , Quimiocinas CC/fisiología , Quimiotaxis de Leucocito/inmunología , Proteínas de Unión al ADN/deficiencia , Proteínas de Unión al ADN/genética , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Receptores de Antígenos de Linfocitos T/inmunología , Receptores CCR , Receptores de Quimiocina/genética , Subgrupos de Linfocitos T/inmunología , Subgrupos de Linfocitos T/metabolismo , Timo/citología , TransfecciónRESUMEN
A pre-TCR-CD3 signal is required for the efficient maturation of CD4- CD8- thymocytes to the CD4+ CD8+ stage. This study addressed whether a similar signal is required for maturation of intestinal intraepithelial lymphocytes (IEL) that may develop extrathymically. We have shown previously that IEL from mice deficient for CD3- associated zeta chains include an immature population of CD3- CD8alphaalpha+ cells expressing cytoplasmic TCR beta chains but lacking detectable surface TCRalphabeta, CD16 and B220. Here we stimulated the appearance of such IEL in epsilon+/- zeta-/- mice by expression of an activated Lck transgene or in vivo treatment with anti-CD3epsilon. Anti-CD3epsilon treatment of RAG-deficient animals also yielded CD16- B220- IEL. In contrast, expression of a TCRbeta transgene in rag-1(-/-) mice did not stimulate the appearance of CD3- CD8alphaalpha+ CD16- B220- cells. Taken together these data indicate that although anti-CD3epsilon treatment and LckF505 assist in catalyzing a CD16+ B220+ --> CD16- B220- transition, these manipulations are not equivalent to a pre-TCR signal in IEL lymphocytes.
Asunto(s)
Mucosa Intestinal/inmunología , Transducción de Señal , Linfocitos T/fisiología , Timo/citología , Animales , Complejo CD3/fisiología , Antígenos CD8/biosíntesis , Diferenciación Celular , Genes Codificadores de la Cadena beta de los Receptores de Linfocito T , Mucosa Intestinal/citología , Mucosa Intestinal/metabolismo , Antígenos Comunes de Leucocito/biosíntesis , Proteína Tirosina Quinasa p56(lck) Específica de Linfocito/genética , Proteína Tirosina Quinasa p56(lck) Específica de Linfocito/metabolismo , Ratones , Complejo Receptor-CD3 del Antígeno de Linfocito T/genética , Complejo Receptor-CD3 del Antígeno de Linfocito T/inmunología , Receptores de Antígenos de Linfocitos T alfa-beta/biosíntesis , Receptores de Antígenos de Linfocitos T alfa-beta/inmunología , Receptores de IgG/biosíntesis , Linfocitos T/citología , Linfocitos T/inmunología , Timo/inmunología , TransgenesRESUMEN
The majority of T cells develop in the thymus and exhibit well characterized phenotypic changes associated with their maturation. Previous analysis of intestinal intraepithelial lymphocytes (IEL) from nude mice and a variety of experimentally manipulated models led to the view that at least a portion of these cells represent a distinct T cell population that matures extrathymically. The IEL that are postulated to mature within the intestine include both T cell receptor (TCR) alpha beta- and gamma delta-bearing subpopulations. They can be distinguished from conventional thymically derived T cells in that they express an unusual coreceptor, a CD8alpha homodimer. In addition, they can utilize the Fc receptor gamma-chain in place of the CD3-associated zeta-chain for TCR signaling and their maturation depends on the interleukin 2 receptor beta-chain. Moreover, TCRalpha beta+CD8alpha alpha+ IEL are not subject to conventional thymic selection processes. To determine whether CD3(-)CD8alpha alpha+ IEL represent precursors of T cells developing extrathymically, we examined IEL from knockout mice lacking the recombination activating gene-1 (rag-1), CD3epsilon, or both Lck and Fyn, in which thymic T cell development is arrested. CD3(-)CD8alpha alpha+CD16(+) IEL from all three mutant strains, as well as from nude mice, included cells that express pre-TCRalpha transcripts, a marker of T cell commitment. These IEL from lck-/-fyn-/- animals exhibited TCR beta-gene rearrangement. However, CD3(-)CD8alpha alpha+CD16(+) IEL from epsilon-deficient mice had not undergone Dbeta-Jbeta joining, despite normal rearrangement at the TCRbeta locus in thymocytes from these animals. These results revealed another distinction between thymocytes and IEL, and suggested an unexpectedly early role for CD3epsilon in IEL maturation.