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Lineage decisions in the thymus: αβ and γδ T cell lineages

Part 2 of 2
Published on December 26, 2021   35 min

Other Talks in the Series: The Immune System - Key Concepts and Questions

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After IL-7 and IL-7 receptor provide the survival signals to early pro-T-cells, the major event in T-cell development occurs, which is the rearrangement of the T-cell receptor genes. The T-cell receptor characterizes T-cells, this is what's different between a T-cell and the other lineages of immune cells, so the rearrangement of the T-cell receptor genes, and the expression of the T-cell receptor, is the key event that will take place in the thymus. This is dependent on a key enzyme called RAG, recombination activating gene, is the enzyme that orchestrates the rearrangement of the T-cell receptor genes, so once again, children that have mutations in RAG will have another type of SCID (severe combined immunodeficiency). In this case it's called Omenn syndrome, after the person who identified it, and it means the absence of both T- and B-cells. In contrast with X-linked SCID described in the previous slide - where T-cells were absent but B-cells were there - in this case, because RAG is not expressed, and RAG is required for both B- and T-cell development, the child will be devoid of both B- and T-cells. This will result in an even more aggressive immunodeficiency. In this case, once again, bone marrow transplantation will be required, so that the child can develop normal B- and T-cells, once it gets healthy bone marrow with healthy T- and B-cell progenitors that can express the RAG protein. What does RAG do?
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Lineage decisions in the thymus: αβ and γδ T cell lineages

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