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Reconstitution of SCID mice with haemopoietic precursors: a detailed analysis of γδ T‐cell reconstitution

A well‐known characteristic of γδ T cells is that they are produced in waves during ontogeny, with cells expressing T‐cell receptor Vγ5 appearing early in fetal thymic ontogeny, followed by Vγ6, then by other γδ T‐cell types. In addition, evidence exists to suggest that the potential of haemopoietic precursors to generate different types of γδ T cells changes in ontogeny. We have used these observations as the basis for an extensive study of the potential for haemopoietic precursors isolated from fetal liver, neonatal spleen and adult bone marrow to reconstitute severe combined immunodeficient (SCID) mice. Mice that were reconstituted as newborns with fetal liver cells most closely resembled normal C.B‐17 mice with respect to both lymphocyte numbers and subsets, while mice reconstituted with adult bone marrow had fewer cells than normal mice. This deficit spanned both T and B cells in all organs examined. Among the γδ T‐cell subsets examined, the ability to reconstitute Vγ4+ cells was particularly dependent on the ontogenic age of the reconstituting presursors, with fetal liver cells having the greatest capacity to generate Vγ4+ cells, and adult bone marrow cells the least. The vast majority of the T cells produced in the reconstituted mice were of donor origin, and the level of reconstitution was found to be dependent upon some factor other than the presursor frequency.