Differential effects of CD4+ and CD8+ cells on lymphocyte development from human cord blood cells in murine fetal thymus explants.
The possibility that mature lymphocytes play a role in the regulation of human T cell development was studied in the experimental model of fetal thymus organ cultures (FTOC), by reconstituting lymphocyte-depleted murine fetal thymus (FT) lobe with cells isolated from human umbilical cord blood (CB). Cultures were incubated with human cytokines (IL-7, FLT-3 ligand and Steel Factor), or remained untreated. When CD4+, or CD8+ CB cells, were co-cultured with FT explants, they expanded and maintained their original phenotypic markers, with no significant effect of the cytokines. Cultures of human hematopoietic stem cells (CD34+) gave rise to CD4+CD8- cells, which were mainly CD3-, with no indication of further intermediate developmental stages. However, a limited number of CD4+CD8+ (double positive [DP]) cells were detected when the CD34- cells were co-cultured with CD4+ cells from the same CB samples. In contrast, FT with unseparated CB cells resulted in the different CD4/CD8 subsets, and their numbers increased in the presence of cytokines. The appearance of DP cells depended on the presence of either CD4+ or CD8+ cells in the cultured CB samples. Hence, DP cells were not detected when the CB was depleted of CD4+ and CD8- cells ("depCB") before culture, and they appeared when depCB were co-cultured with either CD4+ or CD8+ cells. In contrast, CD4+ cells inhibited the development of CD8+CD3+ cells, and this was most pronounced in the absence of the cytokines. There was no symmetrical down-regulatory effect of CD8+ cells on the development of CD4+CD3+ cells. Addition of IL-15 to the cytokine mixture led to an increased proportion of CD56+ cells in cultures of CD34+ cells. The presence of CD4+, and not CD8+ cells, interfered with this process. Our results thus imply differential effects of CD4+ and CD8+ cells on thymocytopoiesis.
Department of Immunology, The Weizman Institute of Science, Rehovot, Israel. lcglober@weizmann.weizmann.ac.il
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Globerson
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Kollet
L
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Abel
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Fajerman
A
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Ballin
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A
Nagler
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Slavin
H B
HB
Hur
Z
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Hagay
A
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Sharp
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Lapidot
D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D000818:Animals; D015703:Antigens, CD; D018952:Antigens, CD34; D000943:Antigens, Differentiation; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology*; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology*; D002450:Cell Communication; D002454:Cell Differentiation; D018920:Coculture Techniques; D005312:Fetal Blood / Q000166:cytology*; D005434:Flow Cytometry; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D008562:Membrane Glycoproteins; D051379:Mice; D009244:NAD+ Nucleosidase; D009924:Organ Culture Techniques; D013950:Thymus Gland / Q000166:cytology* / Q000196:embryology
D015703:Antigens, CD; D018952:Antigens, CD34; D000943:Antigens, Differentiation; D008562:Membrane Glycoproteins; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; C498155:Cd38 protein, mouse; D009244:NAD+ Nucleosidase; D051997:ADP-ribosyl Cyclase 1