Are any functionally mature cells of medullary phenotype located in the thymus cortex?

doi:10.1016/0008-8749(85)90140-6

Cellular Immunology

Volume 93, Issue 2, July 1985, Pages 350-363

https://doi.org/10.1016/0008-8749(85)90140-6 Get rights and content

Abstract

Experiments were undertaken to test if thymocytes of “mature” or “medullary” phenotype were restricted to the medullary area of the thymus. A calculation based on direct cell counts on serial sections indicated that 11.5% of adult male CBA thymic lymphoid cells were within the medullary zone. Since only 3–4% of thymocytes were cortisone resistant, the majority of thymocytes within the medulla were, like cortical thymocytes, cortisone sensitive. A series of cell surface antigenic markers, used alone or in pairs, suggested that 13–15% of thymocytes were of medullary phenotype, somewhat more than the number of thymocytes actually present in the medulla. However, much of this discrepancy could be explained by differential death of cortical cells during isolation and staining, and by the existence in the cortex of a subpopulation of early blast cells which shared some, but not all markers with medullary thymocytes. A direct test for mature or medullary phenotype cells in the cortex involved selective transcapsular labeling of outer-cortical cells with fluorescent dyes, followed by multiparameter immunofluorescent analysis of the 10% labeled population. Outer-cortical thymocytes included some cells (mainly early blasts) sharing some markers with medullary thymocytes, but very few (<1%) of these cells expressed all the characteristic “mature” markers. Limit-dilution precursor frequency studies showed the level of functional cells in the outer cortex was extremely low. The overall conclusion was that the vast majority of cells of complete “mature” phenotype are confined to the thymic medulla. These findings favor the view that thymus migrants originate from the thymic medulla, but do not exclude a cortical origin. The results also illustrate the need for multiparameter analysis to distinguish medullary thymocytes from early blast cells.

References (23)

R.A. Reichert et al.
Cell
(1984)
A. Wilson et al.
J. Immunol. Methods
(1982)
K. Hopper et al.
Cell. Immunol
(1976)
R. Scollay et al.
Thymus
(1983)
D.P. Dialynas et al.
Immunol. Rev
(1983)
R. Ceredig et al.
J. Exp. Med
(1983)
R. Scollay et al.
Immunol. Rev
(1984)
W.-F. Chen et al.
Thymus
(1983)
R. Scollay et al.
J. Immunol
(1980)
R. Scollay
J. Immunol
(1982)

R. Scollay et al.

J. Immunol

(1984)

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Cyclophilin A produced by thymocytes regulates the migration of murine bone marrow cells
2007, Cellular Immunology
Citation Excerpt :
But if the concentrations of such hormones significantly exceed physiological levels, the bulk of thymocytes expire [5]. Only a small cell population, less than 3% of the total number of thymic cells, survives [6]. Cortisone-resistant thymocytes (CRT) are the most mature thymic subpopulation and are located mainly in the medullar zone, representing about 25% of the medulla cells [7].
Supernatant obtained from high dose hydrocortisone resistant thymocytes can induce migration of the bone marrow cell precursors to the periphery. This biological activity depends on the presence of the 18 kDa protein, whose amino acid sequence fits with the sequence of the secretory form of murine cyclophilin A (SP-18). Cyclophilin A isolated from the supernatant of the cortisone-resistant thymoma EL-4 shows its characteristic functional features as it demonstrates isomerase activity and binds with cyclosporine A. The cyclophilin A obtained manifests chemotactic activity that regulates migration of bone marrow cell precursors of neutrophils, T-, B- and dendritic cells.
Functional studies on MEL-14+ and MEL-14− T cells in peripheral lymphoid tissues
1994, Immunobiology
Functions of MEL-14⁺ T cells and MEL-14⁻ T cells in peripheral lymphoid tissues were analyzed and compared. The MEL-14⁻ T cells, representing a minor subpopulation of spleen and lymph node T cells, generated considerably higher mixed lymphocyte reaction and mitogen responses than the MEL-14⁺ T cells in any lymphoid tissues studied. Furthermore, upon stimulation with Con A the MEL-14⁻ CD8⁺ T cells produced significantly larger amounts of IL-2 and IFN-γ than MEL-14⁺ CD8⁺ T cells did. A similar but less marked observation was obtained with the CD4⁺ T cell population. Furthermore, when B10.BR mice were immunized with AKR (Mls-1^a) spleen cells, the proportion of the Mls-1^a reactive Vβ6⁺ T cells from draining lymph nodes increased and a substantial proportion of the increasing Vβ6⁺ T cells was shown to be MEL-14⁻. The present findings on the whole indicate that MEL-14⁻ T cells in the peripheral lymphoid tissues are at functionally high levels and may represent memory cells which have been previously stimulated in vivo.
Quantitative analysis of MEL-14 expression on various lymphocyte subpopulations
1992, Immunobiology
Amounts of gp90^MEL-14 molecules in various lymphocyte subpopulations were analyzed. The expression of gp90^MEL-14 was rapidly up-regulated in the course of usual procedures for preparing single cell suspensions. On the other hand, the gp90^MEL-14 expression was down-modulated after short term culture in the presence of PMA. Addition of NaN₃ in the medium for preparing cell suspension was shown to stabilize the expression profile of the gp90^MEL-14. By this simple improvement, we could successfully evaluate the precise amounts of gp90^MEL-14 expressed on various lymphoid cells which appeared to reflect the expression pattern of gp^90MEL-14in vivo. The proportion of MEL-14⁺ cells and amounts of gp90^MEL-14 on the cells were clearly associated with the anatomical and functional distance from endothelial cells of HEV in peripheral lymph nodes. The present findings, thus, support the role of gp^90MEL-14 molecules as homing receptors for HEV that was originally proposed by WEISSMAN and his colleagues.
Distribution of MEL-14+ Cells in Various Lymphoid Tissues
1991, Immunobiology
The distribution of MEL-14⁺ lymphocytes was investigated by both fluorocytometric analysis and complement-dependent-cellular- cytotoxicity (CDCC) tests in which rabbit antirat Ig was added with complement at a secondary step. When CDCC was employed to detect MEL-14⁺ cells, almost half of the thymocytes were found to be MEL-14⁺ in various strains of mice. This high proportion of MEL-14⁺ cells stands in striking contrast to prior reports. Furthermore, when determined by fluorocytometric analysis, MEL-14⁺ cells were found to comprise more than 80% of the cells in the thymus. The MEL-14⁺ thymocytes comprised both immature subsets (CD4^-8^-, CD4⁺8⁺) and mature subsets (CD4⁺8^-, CD4^-8⁺). MEL-14 brightly positive (MEL-14^high) cells, however, were located mainly in mature T cell subpopulations within the thymus. The MEL-14^high thymocytes appeared to be susceptible to the CDCC method. Most of MEL-14⁺ cells present in spleens and lymph nodes were shown to be included in the MEL-14^high population. The MEL-14⁺ cells susceptible to treatment with MEL-14, rabbit anti-rat Ig plus complement in the spleen and lymph node were restricted to cells of the T-lineage. These data suggest that T cells may change from cells with low expression of the MEL-14 antigens at their surface to cells with high MEL-14 antigens in the process of differentiation. Furthermore, these findings indicate that MEL-14 molecules may be used as a surface marker to characterize an important T cell subpopulation.
Selection of CD4+CD8+ thymocytes by complex formation with medulla-derived epithelial cells
1990, Cellular Immunology
The role of lymphostromal complexes in T-cell differentiation is far from elucidated, mainly because a clear association of a particular stromal cell type with a distinct thymocyte subset has never been identified. Using an in vitro system, detecting the adherence of thymocytes to a thymic medullary epithelial cell line (E-5), we showed that the phenotype of these thymocytes was that of cortical type: Thy-1^hi, LFA-1⁺, PNA^hi, CD4⁺CD8⁺, MEL-14^−/lo, IL-2R⁻, CD3_ϵ^−/lo, and TcR V_β8^−/lo. They were enriched in cells in G₂/M at the time of complex formation, showed a higher basal proliferation in culture, and did not respond to PHA, IL-2 and only marginally to Con A. These data show that complex formation with mouse thymic medullary epithelium selects for CD4⁺CD8⁺ thymocytes, as shown by the marked decrease in $CD 4^{+} CD 8^{−} CD 4^{−} CD 8^{+}$ thymocytes, and the incapacity of CD4⁻CD8⁻ thymocytes to adhere.
Immunohistological analysis of immigration of thymocyte-precursors into the thymus: Evidence for immigration of peripheral T cells into the thymic medulla
1989, Cellular Immunology
The immigration route of thymocyte precursors into the thymic microenvironment was examined in various experiments using two strains of mice (B10.Thy-1.1 and C57BL/6) that were identical in H-2 and different in Thy-1 locus. The experiment of thymus grafting revealed that there were two types of thymocyte precursors; one immigrated into the cortex and vigorously proliferated and the other directly immigrated into the medulla. Such a direct immigration of host-type cells into the medulla of the grafted thymus was not observed, when thymus was grafted into young adult nude mice having no T cells. When bone marrow cells were iv injected into intact mice, the direct immigration of donor-type cells was observed only in the cortex, not in the medulla. In parabiotic mice, the immigration of partner's cells into the medulla was observed independently before the proliferation of partner's cell in the cortex. These findings taken together indicate that peripheral T cells directly immigrate into and recirculate through the thymic medulla.

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^☆: Supported by the National Health and Medical Research Council, Australia, by the C. H. Warman Research Fund, and by the National Institutes of Health Grant AI-17310.

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Cellular Immunology

Abstract

References (23)

Cell

J. Immunol. Methods

Cell. Immunol

Thymus

Immunol. Rev

J. Exp. Med

Immunol. Rev

Thymus

J. Immunol

J. Immunol

J. Immunol

Cited by (19)

Cyclophilin A produced by thymocytes regulates the migration of murine bone marrow cells

Functional studies on MEL-14<sup>+</sup> and MEL-14<sup>−</sup> T cells in peripheral lymphoid tissues

Quantitative analysis of MEL-14 expression on various lymphocyte subpopulations

Distribution of MEL-14<sup>+</sup> Cells in Various Lymphoid Tissues

Selection of CD4<sup>+</sup>CD8<sup>+</sup> thymocytes by complex formation with medulla-derived epithelial cells

Immunohistological analysis of immigration of thymocyte-precursors into the thymus: Evidence for immigration of peripheral T cells into the thymic medulla

Are any functionally mature cells of medullary phenotype located in the thymus cortex?☆

Abstract

Cell

J. Immunol. Methods

Cell. Immunol

Thymus

Immunol. Rev

J. Exp. Med

Immunol. Rev

Thymus

J. Immunol

J. Immunol

J. Immunol