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lck-Driven Cre Expression Alters T Cell Development in the Thymus and the Frequencies and Functions of Peripheral T
Berit Carow1, Yu Gao2, Jonathan Coquet2
1Department of Microbiology, Tumor, and Cell Biology, Karolinska Institutet, S 171 77 Stockholm, Sweden; and Berit.Carow@ki.se.
Abstract:
Conditional gene targeting using the bacteriophage-derived Cre recombinase is widely applied for functional gene studies in mice. Mice transgenic for Cre under the control of the lck gene promoter are used to study the role of loxP-targeted genes in T cell development and function. In this article, we show a striking 65% reduction in cellularity, preferential development of γδ versus αβ T cells, and increased expression of IL-7R in the thymus of mice expressing Cre under the proximal lck promoter (lck-cre(+) mice). The transition from CD4/CD8 double-negative to double-positive cells was blocked, and lck-cre(+) double-positive cells were more prone to apoptosis and showed higher levels of Cre expression. Importantly, numbers of naive T cells were reduced in spleens and lymph nodes of lck-cre(+) mice. In contrast, frequencies of γδ T cells, CD44(+)CD62L(-) effector T cells, and Foxp3(+) regulatory T cells were elevated, as was the frequency of IFN-γ-secreting CD4(+) and CD8(+) T cells. A literature survey of 332 articles that used lck-cre(+) mice for deletion of floxed genes indicated that results are statistically influenced by the control used (lck-cre(+) or lck-cre(-)), more frequently resembling the lck-cre(+) phenotype described in this article if lck-cre(-) controls were used. Altogether, care should be taken when interpreting published results and to properly control targeted gene deletions using the lck-cre(+) strain.
Insights
Conditional gene targeting in mice using Lck-Cre transgenic models reveals significant impacts on T cell development. Researchers found altered T cell populations and increased apoptosis, highlighting the need for careful experimental controls in T cell studies.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Conditional gene targeting with Cre recombinase is crucial for studying gene function in mice.
- Lck promoter-driven Cre expression (lck-cre) is used to investigate T cell development and function.
Purpose of the Study:
- To characterize the effects of Cre recombinase expression under the proximal lck promoter on T cell development.
- To assess the impact of lck-cre on T cell populations in thymus, spleen, and lymph nodes.
- To evaluate the influence of control groups on the interpretation of studies using lck-cre mice.
Main Methods:
- Analysis of T cell populations in the thymus, spleen, and lymph nodes of lck-cre(+) mice.
- Flow cytometry to assess cell surface markers (CD4, CD8, IL-7R, CD44, CD62L, Foxp3).
- Assessment of apoptosis and cytokine production (IFN-γ).
- Literature survey of studies utilizing lck-cre(+) mice.
Main Results:
- A 65% reduction in thymic cellularity with a shift towards γδ T cells over αβ T cells.
- Blocked transition from double-negative to double-positive thymocytes, increased apoptosis, and elevated Cre expression in lck-cre(+) cells.
- Reduced naive T cells in peripheral lymphoid organs, but increased frequencies of γδ T cells, effector T cells, regulatory T cells, and IFN-γ-secreting T cells.
Conclusions:
- Lck-driven Cre expression profoundly impacts T cell development and homeostasis.
- Published results using lck-cre(+) mice may be statistically influenced by the choice of control group.
- Careful consideration of experimental controls is essential for accurate interpretation of lck-cre mouse studies.
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