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Published on: March 6, 2010
Murine CD4-CD8- thymocytes are stimulated by interleukin-2 to proliferate in vitro in chemically defined medium
1Department of Pathology and Oncology, University of Kansas Medical Center, Kansas City 66103.
Insights
Fetal and adult CD4-CD8- thymocytes proliferate in response to Interleukin-2 (IL-2) in vitro. Interleukin-1 (IL-1) enhances this proliferation in fetal cells, suggesting cooperative roles in T cell development.
Area of Science:
- Immunology
- Developmental Biology
- Cell Biology
Background:
- Thymocyte development is crucial for adaptive immunity.
- The roles of Interleukin-1 (IL-1) and Interleukin-2 (IL-2) in early T cell proliferation are not fully understood.
- Understanding thymocyte responses in defined media is key to dissecting cytokine signaling.
Purpose of the Study:
- To investigate the proliferative capacity of fetal and adult CD4-CD8- thymocytes in response to IL-2 and IL-1.
- To determine the effect of IL-1 and IL-2 co-stimulation on thymocyte proliferation.
- To explore the role of IL-2 receptors in mediating thymocyte proliferation.
Main Methods:
- Culturing fetal and adult mouse thymocytes, including purified CD4-CD8- populations, in serum-free medium.
- Assessing proliferation in the presence and absence of IL-2 and IL-1.
- Utilizing anti-IL-2 receptor antibodies to block signaling.
Main Results:
- Both fetal and adult CD4-CD8- thymocytes proliferated in response to IL-2.
- IL-1 significantly enhanced IL-2-induced proliferation in fetal thymocytes by increasing IL-2 receptor expression.
- IL-1 showed a less pronounced additive effect on adult CD4-CD8- thymocyte proliferation.
- Proliferation was dependent on IL-2 receptor signaling.
Conclusions:
- Fetal and adult CD4-CD8- thymocytes are capable of IL-2-dependent proliferation in vitro.
- IL-1 and IL-2 likely cooperate to stimulate T cell proliferation during thymic development in vivo.
- These findings contribute to understanding the cytokine milieu regulating T cell maturation.
Abstract:
The ability of fetal and young adult CD4-CD8- thymocytes to proliferate in chemically defined (serum-free) medium in the presence and absence of IL-2 was examined. Dissociated thymocytes from day 15 and older fetal mice proliferated in vitro in the presence but not the absence of IL-2. The degree of proliferation was increased by including IL-1 with the IL-2. Inclusion of IL-1 in cultures of fetal thymocytes was associated with an increase in the number of IL-2 receptor positive cells, relative to cultures containing IL-2 alone. Although unfractionated thymocytes failed to proliferate in chemically defined medium, CD4-CD8- cells purified from thymic cell suspensions from young adult mice from several inbred strains proliferated to a limited extent in the absence of added cytokines. Proliferation was augmented 40-100 fold by inclusion of IL-2 in cultures. IL-1 stimulated some proliferation by young adult CD4-CD8- cells, but, unlike the effect of IL-1 and IL-2 on fetal thymocytes, combination of IL-1 with IL-2 did not have a notable additive effect on IL-2 induced proliferation. Proliferation stimulated by both IL-1 and IL-2 was completely abrogated by inclusion of anti-IL-2 receptor antibody in the cultures. Thymocytes from F1 progeny of inbred strains of mice proliferated to a greater extent in the absence of IL-2 than did thymocytes from either parent strain, although the response to IL-2 was not significantly different. The data demonstrate that both fetal and adult CD4-CD8- thymocytes area capable of proliferating in response to IL-2 in vitro, suggesting that, as is the case during antigen specific responses by mature T cells, IL-1 and IL-2 cooperate to stimulate T cell proliferation during development in vivo.
