| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
*
Department of Internal Medicine Clinical Immunology, Allergy and Respiratory Disease Unit, and
Department of Physiopathology, Endocrinology Unit, University of Florence, Florence, Italy;
Apuanic Pediatric Hospital, Massa-Carrara, Italy; and
§
Icos, Bothell, WA 98011
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Stromal-derived factor-1 seems to attract prevalently immature thymocytes (both CD4-CD8- and CD4+CD8+), thus favoring their migration at premedullar stage (cortex) before and during positive selection (26, 27). By contrast, ELC and SLC prevalently attract mature single-positive (CD4+CD8- or CD4-CD8+) thymocytes, suggesting their role in the migration from the thymus to the circulation of cells that have already passed both positive and negative selection (26, 27, 28). Murine thymocytes at cortical, transitional between cortex and medulla, and early medullary stages respond equally well to TECK, but all responsiveness is lost in the most mature medullary phenotype (29). By contrast, TECK efficaciously attracts both double-positive and single-positive human thymocytes (25). Recently, we (28) and others (29) have shown that MDC attracts a small population of CD3+CD4+CD8low thymocytes that corresponds to cells transitional between cortex and medulla and in early medullary stages. In human thymus, MDC was found to be selectively localized to epithelial cells scattered in the medullary areas and in the outer walls of Hassal’s corpuscles (28), supporting its possible role in the attraction of thymocytes from the cortex to the medulla or within the medulla, where they may undergo negative selection.
In this study, we have examined the chemotactic activity of MDC, ELC, and SLC on human thymocytes. Moreover, we have characterized the cells that produce ELC and their possible relationship with MDC-producing cells in the human thymus. As in the mouse, both ELC and SLC caused the selective accumulation of single-positive (CD4+CD8- or CD4-CD8+) thymocytes, and expressed CD45RA, but not CD30, whereas a remarkable proportion of MDC-responsive thymocytes were double-positive (CD4+CD8+) cells that had reduced levels of CD8, and expressed CD30, but not CD45RA. More importantly, ELC production within the human thymus was a property of medullary epithelial cells, but ELC-producing cells were clearly distinct from those producing MDC. MDC-producing cells expressed high levels of CD30L and were consistently found on the outer wall of Hassal’s corpuscles, whereas ELC-producing cells often localized around small vessels, but they were not found on the outer wall of Hassal’s corpuscles and did not express CD30L.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
FITC-, PE-, allophycocyanin-, and peridin chlorophyll
protein-conjugated anti-CD3 (SK7), anti-CD4 (SK3), anti-CD8
(SK1), anti-CD69 (L78), anti-CD45RO (UCLH1), and
anti-CD45RA (L48) mAbs were purchased from Becton Dickinson
(Mountain View, CA). FITC-conjugated anti-CD30 (Ber-H2) mAb was
from Dako (Gastrup, Denmark). Anti-CD3 (UCHT1) mAb was from PharMingen
(San Diego, CA), anti-CD30 (HRS4) from Immunotech (Marseille,
France), anti-CD30L (M81) from Genzyme Diagnostics (Cambridge, MA),
anti-CD68 (EBM11) from Dako, anti-CD83 (HB15e) from PharMingen,
and anti-pan-cytokeratin (CK) (C11) from Sigma Immunochemicals
(Milan, Italy). The anti-peptidylglycine 
-amidating
monooxygenase (PAM)-1 mAb was a kind gift of A. Mantovani (Milano,
Italy). The anti-von Willebrand factor (vWf) rabbit anti-human
polyclonal Ab was from Dako. The preparation of anti-MDC (252Y) mAb
has been previously reported, and its specificity was validated by
several approaches, as described (28, 30, 31). Two mAbs
specific for human ELC (326 M and 326N) were obtained and characterized
using standard procedures, as described previously for MDC
(28). In vitro characterization of these Abs revealed that
326 M inhibits ELC bioactivity, while 326N does not, suggesting that
they identify distinct epitopes on ELC (unpublished results). The 326 M
Ab gave stronger immunoreactivity than the 326N Ab, and therefore it
was used for immunostaining experiments. The anti-CCR4 mAb was
generated using L1.2/CCR4 cells as Ag and was selected for specific
recognition of CCR4 transfectants by FACS (unpublished results). The
anti-CCR4 mAb was conjugated with Cy5 protein by the conjugation
kit following manufacturer’s instructions (Amersham Life Science
Italia, Milan, Italy). All of the isotype-matched control Abs were
purchased from Southern Biotechnology Associates (Birmingham,
AL).
MDC and ELC were expressed in Chinese hamster ovary cells, and the recombinant proteins were purified to homogeneity, as described previously (13). The purity of these proteins was confirmed by N-terminal amino acid analysis and mass spectrometry. Biological activity was measured by chemotaxis of L1.2 cells stably transfected with CCR4 (MDC) or CCR7 (ELC) and was equivalent to that found for commercially available preparations of these chemokines (unpublished results). Human rSLC was obtained from R&D Systems (Minneapolis, MN).
Human thymuses
Normal postnatal thymus specimens were obtained from 12 children, aged between 5 days and 3 years, during corrective cardiac surgery at the Apuano Pediatric Hospital of Massa Carrara. The procedures followed in the study were in accordance with the ethical standards of the responsible Regional Committee on human experimentation.
Cytofluorometric analysis of thymocyte suspensions and purification of CD4+CD8- thymocytes
Thymic tissue fragments were gently passed through a stainless steel mesh to obtain single-cell suspensions from which MNC were separated by centrifugation on Ficoll-Hypaque gradient. Thymic MNC were resuspended in PBS containing 0.5% BSA and 0.02% sodium azide, and then incubated with FITC-, PE-, allophycocyanin-, or peridin chlorophyll protein-conjugated anti-CD3, anti-CD4, anti-CD8, anti-CD30, anti-CD45RO, anti-CD45RA, anti-CD69, or Cy5-conjugated anti-CCR4 mAb. Cell surface marker analysis was performed on a FACSCalibur cytofluorometer (Becton Dickinson).
Purification of CD4+CD8- thymocytes was performed by high gradient magnetic cell sorting, as described elsewhere (32). Briefly, MNC were incubated for 20 min with a cocktail of hapten-conjugated Abs (CD8, CD11b, CD16, CD19, CD36, and CD56), extensively washed, and then incubated for additional 20 min with anti-hapten polyclonal Ab conjugated to magnetic cell sorter (MACS) colloidal superparamagnetic microbeads system (Milteny Biotec GmbH, Bergisch Gladbach, Germany). After washing, cells were separated on a VS+/LS+ column, inserted into a MidiMACS magnet. Unlabeled cells, collected as negative fraction, consisted of >95% CD4+CD8- cells.
Cloning and sequencing of the CCR4 probe
mRNA was extracted from activated peripheral blood MNC and reversed to first strand cDNA by oligo(dT) primer, using a first strand synthesis kit (Stratagene, Cambridge, MA). Amplification of the first strand products was conducted in a thermal cycler (Idaho Technology, Idaho Falls, ID). The samples were subjected to 30 cycles of amplification using 10 pM of each primer (32) and 0.5 U of Taq DNA polymerase in 10-1 volume. The DNA fragment of 500 bp amplified by PCR was subcloned in pGEM-T easy (Promega, Madison, WI), according to the manufacturer’s instructions. Sequencing of the amplified product was performed by the dideoxynucleotide chain-termination method (32), by using [35S]dATP and sequenase enzyme (United States Biochemical, Cleveland, Ohio).
In situ hybridization
In situ hybridization was performed on frozen thymus sections by
using sense or antisense CCR4 RNA probes. To do this, the plasmid
containing the CCR4 cDNA was subcloned in PGEM-4Z and then linearized
with XbaI or HindIII restriction enzymes,
followed by phenol-chloroform extraction and ethanol precipitation.
Thereafter, sense and antisense RNA probes were synthesized using SP6
or T7 RNA polymerases (Riboprobe Gemini System; Promega) in the
presence of 35S -thio-UTP (1300 mCi/mmol; NEN
DuPont, Paris, France). Frozen thymus sections were mounted onto
gelatin-coated slides and fixed with 4% paraformaldehyde for 20 min at
room temperature. Sections were subsequently treated with 0.2 N HCl for
20 min, pronase (0.125 mg/ml) for 10 min, 0.1 M glycine for 30 s,
and 4% paraformaldehyde for 20 min. Then, sections were rinsed with
PBS and acetylated and dehydrated in increasing ethanol concentrations.
A total of 30 µl of the hybridization solution (40% formamide, 4x
SSC, 10 mM DTT, 1x Denhardt’s solution, 10% dextran sulfate, 0.1
mg/ml sheared herring sperm DNA, and 1 mg/ml yeast tRNA), containing
8 x 105 cpm of
35S-labeled human CCR4 RNA antisense probe, was
applied to each section and covered with parafilm. Hybridization was
conducted at 52°C for 16 h. Removal of the nonspecifically bound
probe by RNase digestion and autoradiography were performed, as
detailed elsewhere (32). Sections were subsequently
counterstained with Mayer’s hematoxylin and mounted with Kaiser’s
glycerol gelatin. An average of five sections was analyzed for each
tissue sample. Negative controls consisted of hybridization to a sense
RNA probe.
Immunohistochemistry
Immunohistochemical staining was performed on 10-µm cryostat sections or cultured cells fixed in 4% paraformaldehyde for 20 min or in acetone for 10 min. Sections were subsequently exposed to 0.3% hydrogen peroxide-methanol solution to quench endogenous peroxidase activity. After a 30-min preincubation with normal horse serum (Vectastain ABC kit; Vector Laboratories, DBA, Milan, Italy), sections were layered for 30 min with anti-MDC (5 µg/ml), anti-ELC (1 µg/ml), anti-CD30 (4 µg/ml), anti-CD30L (10 µg/ml), anti-CD3 (1 µg/ml), anti-CD68 (3 µg/ml), anti-CD83 (10 µg/ml), and anti-CK (2 µg/ml) mAbs, followed by biotinylated anti-mouse IgG Ab, or anti-vWf polyclonal rabbit Ab (0.02 µg/ml), followed by goat anti-rabbit IgG, and the avidin-biotin-peroxidase complex (Vectastain ABC kit), as described (32). The 3-amino-9-ethylcarbazole (Sigma), VECTOR SG, or VECTOR VIP (Vector Laboratories) were used as peroxidase substrates. Finally, sections were counterstained with Gill’s hematoxylin and mounted with Kaiser’s glycerol gelatin. All incubations were performed at room temperature. As negative control, primary Ab was replaced with an isotype-matched Ab with irrelevant specificity or mouse ascites fluid.
Double immunostaining was performed by using the avidin-biotin-peroxidase system with two different substrates, as described (32). To identify on the same specimen two different proteins, the 3-amino-9-ethyl-carbazole or VECTOR VIP (red color) and the VECTOR SG (bluish grey) substrates were used, respectively. After double immunostaining, sections were counterstained with methyl green and mounted with Kaiser’s glycerol gelatin.
Chemotaxis assay
The chemotaxis assay was performed according to a technique
previously described (28). Briefly,
107 freshly isolated thymocytes were
resuspended in 1.1 ml of RPMI 1640 containing 0.5% BSA and loaded into
the upper well of a transwell chamber (3-µm pore size, six wells;
Costar, Corning, NY). Chemokine was added in the same buffer to the
lower well in a volume of 1.6 ml. After 4 h at 37°C, cells
present in the lower chamber were collected and counted. Data were
expressed as the mean number of cells that migrate through the filter.
Each experiment was performed in triplicate at least three times,
unless otherwise indicated. Cells that migrated in the absence of
chemokines served as a negative control.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
To establish whether MDC, ELC, and SLC had chemoattractant
activities on human thymocyte populations corresponding to those
already described in mice (26, 28, 29), the chemotaxis of
MNC suspensions from three postnatal human thymuses to these chemokines
was analyzed. Each chemokine was used at different concentrations, and
the concentration giving the maximal thymocyte migration into the lower
chamber was defined as the optimal concentration to be used in
subsequent experiments. Of note, the optimal concentration for MDC was
10 nM and its increase resulted in a decrease of the number of
migrating cells. By contrast, there was a dose-dependent increase in
the number of cells migrating in response to ELC or SLC, the optimal
concentration being 1 µM (Fig. 1
).
Checkerboard analysis confirmed that all responses were chemotactic
with little chemokinetic component (data not shown). Thymocytes
responded well to ELC and SLC, whereas the number of thymocytes that
migrated in response to MDC was much lower (Fig. 1).
|
). This
finding did not simply reflect CD3 modulation by cell incubation at
37°C or by chemokines, because no changes were observed in the input
population tested at different times after incubation under the same
experimental conditions used in the chemotaxis assay (data not shown).
Fig. 2 also shows that, although ELC, SLC, and MDC all attracted a
remarkable population of double-positive
CD4+CD8+ thymocytes, there
was a clear difference in the chemoattractant activity of ELC/SLC and
MDC. While ELC and SLC caused the prevalent attraction of
single-positive (CD4+CD8-
or CD4-CD8+) cells, MDC
induced the prevalent migration of double-positive
CD4+CD8+ cells showing
reduced levels of CD8
(CD4+CD8low), and of a
small subset of single-positive
CD4+CD8- cells.
|
To better establish the nature of MDC-responsive cells in human
thymus, the expression of MDC receptor, CCR4, was assessed in three
postnatal human thymuses by in situ hybridization. As shown in Fig. 3, CCR4 mRNA expression was found to be
selectively localized to the medullary areas, whereas in the cortical
areas no CCR4 mRNA-expressing cells were observed.
|
, CD30+ cells were
indeed enriched within the CD3+ thymocyte subset
that migrated in response to MDC. Moreover, the majority of
CD30+ cells in the MDC-responsive population were
double-positive CD4+CD8low
cells (Fig. 4). Double staining of thymocytes with anti-CCR4 and
anti-CD30 Ab showed that virtually all CCR4+
thymocytes were CD30+, although a remarkable
proportion of CCR4-CD30+
cells was also observed (Fig. 5). The
majority of CD30+ thymocytes were
CD4+CD8low cells, and some
of them apparently exhibited CD4, but not CD8, expression (Fig. 5).
|
|
A) and showed different
expression of other surface markers. All MDC-responsive
CD4+CD8- thymocytes were
CD69+, and a remarkable proportion of them
expressed CD30, whereas not all
CD4+CD8- ELC-responsive
thymocytes were CD69+ and virtually none of them
expressed CD30 (Fig. 6B). In addition, the great majority of
MDC-responsive cells were
CD45RA-CD45R0+, whereas
the ELC-responsive population consisted of a mixture of
CD45RA-CD45R0+,
CD45RA+CD45R0-, and
CD45RA+CD45R0+ cells (Fig. 6C).
|
The possibility that MDC and ELC were produced by the same or
different cell types was then investigated in four postnatal human
thymuses by using immunohistochemistry. Both MDC and ELC reactivity
appeared to be selectively localized to cells scattered in the
medullary areas, whereas neither MDC- nor ELC-positive cells were found
in the cortex (Fig. 7, A and
B). However, MDC reactivity was consistently localized to
the outer wall of Hassal’s corpuscles, as reported (28),
whereas ELC reactivity was only rarely found in Hassal’s corpuscles
(Fig. 7, C and D), whereas it was widely
expressed in the inner medulla and around vessels present in proximity
of cortico-medullary junctions (Fig. 7, E and F).
Moreover, double immunostaining for MDC and ELC showed clear-cut
separation between the two types of cells (Fig. 7G), the
proportion of cells costaining for ELC and MDC being lower than 5%
(data not shown).
|
A), CD68 (Fig. 8B), CD83 (Fig. 8C), and PAM-1 (Fig. 8D), whereas CD83 and PAM-1 usually colocalized (Fig. 8E). By contrast, the majority of, even not all, MDC- and
ELC-reactive cells stained positive for CK (Fig. 8F).
Finally and most importantly, CD30L reactivity was never found on
ELC-producing cells (Fig. 8G), while all MDC-producing cells
also stained positive for CD30L (Fig. 8H), suggesting that
ELC expression within the human thymus is mainly a property of a subset
of medullary epithelial cells distinct from those producing MDC and
expressing CD30L.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Based on our previous data obtained in murine thymus (28), we have suggested that MDC may induce the migration of thymocytes that have already passed positive, but not negative, selection from the cortex into the medulla. The observations presented in this study, that cells expressing the MDC receptor (CCR4) are detectable in the medulla, but not in the cortex, suggest that MDC-responsive thymocytes are already localized to the medullary areas. Consistent with this, a small proportion of MDC-responsive cells were CD4+CD8-, as the majority of ELC- or SLC-responsive thymocytes. However, the majority of MDC-responsive cells were CD45RA-, whereas ELC-responsive thymocytes consisted of a mixture of CD45RA+RO-, CD45RA+RO+, and CD45RA-RO+ cells. Taken together, these data suggest that responsiveness to MDC is a property of thymocytes that have migrated from the cortex to the medulla, and that have passed the positive selection, as also demonstrated by their expression of CD69 (27), but that are in an earlier stage of development compared with ELC- or SLC-responsive cells.
The most interesting observation emerging from this study, however, is that MDC-responsive CCR4+ thymocytes were enriched in CD30+ cells, whereas ELC-responsive thymocytes did not express CD30, a T cell activation molecule whose expression is dependent of either CD28 ligation or the activity of IL-4 (34, 35, 36). This finding, together with the demonstration that the great majority of MDC-responsive cells were CD45RA-RO+, suggests that these cells become activated into the medulla. In contrast, the lack of CD30 and the lesser expression of CD45RO by ELC-responsive thymocytes suggest that they do not undergo the same activation process into medullary areas and, therefore, move toward a different destiny.
The results of this study also suggest that, while the production of ELC by other cell types cannot be surely ruled out, ELC protein expression is mainly a property of medullary epithelial cells distinct from those producing MDC. Indeed, ELC-producing cells were rarely detected in the outer walls of Hassal’s corpuscles, while some localized around the small vessels mainly present in the cortico-medullary junctions. The latter finding is consistent with the possibility that ELC-producing cells favor the migration into the circulation of mature thymocytes that have survived the process of negative selection. In addition, the usual absence of ELC reactivity in Hassal’s corpuscles, which consistently express MDC, provides additional support to the concept that ELC- and MDC-producing medullary epithelial cells are involved in different functional processes. Indeed, although we cannot even exclude the production of MDC by other cell types in the thymic medulla, it is quite clear that MDC protein and hence the chemotactic gradient are mainly established around Hassal’s bodies. In this regard, it is noteworthy that cells present in the outer wall of Hassal’s corpuscles and most MDC-producing epithelial cells scattered in the medulla also express high concentrations of CD30L, whereas ELC-producing medullary epithelial cells do not. The association between CD30L expression and MDC production is further supported by the observation that lines of thymic epithelial cells expressing CD30L established from human thymuses (32) produced in their supernatants MDC amounts at least 10 times higher than CD30L-negative cell lines (data not shown).
CD30-CD30L interactions in murine thymus have been suggested to play a role in the programmed cell death of thymocytes (33, 34, 35, 36, 37), thus probably contributing to the process of negative selection (32, 33, 37). Moreover, CD30 signaling has been found to limit the proliferative potential of autoreactive CD8+ effector T cells and protect the body against autoimmunity (38). Thus, it is tempting to speculate that MDC-producing epithelial cells not only attract CCR4+ thymocytes that have already passed the positive selection and have migrated to the medulla, but are also responsible for their activation and CD30 expression by presenting the appropriate peptide on their surface and hence provide the CD30L-mediated apoptotic signal. Indeed, it has clearly been shown that medullary epithelial cells can express different autoantigens (39, 40, 41, 42, 43), which suggests the concept of medullary thymic epithelium as a mosaic of epithelial self (44), and possess all the potential to mediate directly the process of negative selection (45, 46, 47). By contrast, the CCR4+ thymocytes that do not possess a TCR reactive with the peptide presented by the MDC-producing CD30L+ epithelial cells responsible for their attraction cannot be activated, do not express CD30, and therefore cannot receive the CD30L-mediated apoptotic signal. Thereafter, they can migrate into the circulation in response to the chemoattractant effect of ELC- and/or SLC-producing medullary epithelial cells.
An intriguing point, which may argue against this hypothesis, comes
from the recent observation that CCR7 gene-deficient mice do not appear
to have any obvious problem in the T cell development in the thymus
(48). However, this apparent discrepancy may simply
reflect the redundancy in the chemoattractant activities of different
thymocyte subsets during T cell development in thymus. For example, it
has been shown that TECK efficaciously induced chemotaxis of mature
thymocytes by interacting with the CCR9 receptor (8, 24, 25). In addition, we have recently found that IFN-inducible
protein-10, monokine induced by IFN-
, and IFN-inducible T cell
chemoattractant selectively attract mature CD8+
human thymocytes, as well as other thymic cell subsets, via their
interaction with CXCR3 receptor (unpublished results). Obviously,
additional studies are required to fully validate our
hypotheses.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 F.A. and P.R. contributed equally to this work.
3 Address correspondence and reprint requests to Dr. Sergio Romagnani, Department of Internal Medicine, Viale Morgagni, 85 Firenze-50134, Italy.
4 Abbreviations used in this paper: TECK, thymus-expressed chemokine; CK, cytokeratin; CXCR, CXC chemokine receptor; ELC, EBI1-ligand chemokine; MDC, macrophage-derived chemokine; MNC, mononuclear cell; PAM-1, peptidylglycine -amidating monooxygenase-1; SLC, secondary lymphoid tissue chemokine; vWf, von Willebrand factor.
Received for publication December 27, 1999. Accepted for publication April 14, 2000.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
-inducible protein-10 in lymphoid organs and inducible expression in T cells and thymocytes. J. Exp. Med. 179:1373. and MIP-3ß. J. Immunol. 158:1033.[Abstract]
chemoattractant (I-TAC): a novel non-ELR CXC chemokine with potent activity on activated T cells through selective high affinity binding to CXCR3. J. Exp. Med. 187:2009. on macrophage-derived chemokine production: an amplification circuit of polarized T helper 2 responses. Blood 92:2668.. J. Immunol. 158:2090.[Abstract]
on CD30 and lymphocyte activation gene-3 (LAG-3) expression by activated naive T cells. Eur. J. Immunol. 27:2239.[Medline]
This article has been cited by other articles:
|
|
 |
|
  X. Yin, E. Ladi, S. W. Chan, O. Li, N. Killeen, D. J. Kappes, and E. A. Robey CCR7 Expression in Developing Thymocytes Is Linked to the CD4 versus CD8 Lineage Decision J. Immunol., December 1, 2007; 179(11): 7358 - 7364. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Hirota, Y. Osuga, K. Koga, O. Yoshino, T. Hirata, C. Morimoto, M. Harada, Y. Takemura, E. Nose, T. Yano, et al. The Expression and Possible Roles of Chemokine CXCL11 and Its Receptor CXCR3 in the Human Endometrium J. Immunol., December 15, 2006; 177(12): 8813 - 8821. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. H. D. Gray, N. Seach, T. Ueno, M. K. Milton, A. Liston, A. M. Lew, C. C. Goodnow, and R. L. Boyd Developmental kinetics, turnover, and stimulatory capacity of thymic epithelial cells Blood, December 1, 2006; 108(12): 3777 - 3785. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F Annunziato, L Cosmi, F Liotta, E Lazzeri, P Romagnani, R Angeli, L Lasagni, R Manetti, F Marra, C Gerard, et al. CXCR3 and {alpha}E{beta}7 integrin identify a subset of CD8+ mature thymocytes that share phenotypic and functional properties with CD8+ gut intraepithelial lymphocytes Gut, July 1, 2006; 55(7): 961 - 968. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Kwan and N. Killeen CCR7 Directs the Migration of Thymocytes into the Thymic Medulla J. Immunol., April 1, 2004; 172(7): 3999 - 4007. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Cosmi, F. Liotta, E. Lazzeri, M. Francalanci, R. Angeli, B. Mazzinghi, V. Santarlasci, R. Manetti, V. Vanini, P. Romagnani, et al. Human CD8+CD25+ thymocytes share phenotypic and functional features with CD4+CD25+ regulatory thymocytes Blood, December 1, 2003; 102(12): 4107 - 4114. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. H. Kim, K. Nagata, and E. C. Butcher Dendritic Cells Support Sequential Reprogramming of Chemoattractant Receptor Profiles During Naive to Effector T Cell Differentiation J. Immunol., July 1, 2003; 171(1): 152 - 158. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Erickson, S. Morkowski, S. Lehar, G. Gillard, C. Beers, J. Dooley, J. S. Rubin, A. Rudensky, and A. G. Farr Regulation of thymic epithelium by keratinocyte growth factor Blood, October 16, 2002; 100(9): 3269 - 3278. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. Annunziato, L. Cosmi, F. Liotta, E. Lazzeri, R. Manetti, V. Vanini, P. Romagnani, E. Maggi, and S. Romagnani Phenotype, Localization, and Mechanism of Suppression of CD4+CD25+ Human Thymocytes J. Exp. Med., August 5, 2002; 196(3): 379 - 387. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Zaitseva, T. Kawamura, R. Loomis, H. Goldstein, A. Blauvelt, and H. Golding Stromal-Derived Factor 1 Expression in the Human Thymus J. Immunol., March 15, 2002; 168(6): 2609 - 2617. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. R. Taylor Jr., K. C. Kimbrell, R. Scoggins, M. Delaney, L. Wu, and D. Camerini Expression and Function of Chemokine Receptors on Human Thymocytes: Implications for Infection by Human Immunodeficiency Virus Type 1 J. Virol., September 15, 2001; 75(18): 8752 - 8760. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Romagnani, F. Annunziato, E. Lazzeri, L. Cosmi, C. Beltrame, L. Lasagni, G. Galli, M. Francalanci, R. Manetti, F. Marra, et al. Interferon-inducible protein 10, monokine induced by interferon gamma, and interferon-inducible T-cell alpha chemoattractant are produced by thymic epithelial cells and attract T-cell receptor (TCR) {alpha}{beta}+CD8+ single-positive T cells, TCR{gamma}{delta}+ T cells, and natural killer-type cells in human thymus Blood, February 1, 2001; 97(3): 601 - 607. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
).
