Immature T cells in peripheral lymphoid organs of recombinase-activating gene-1/-2-deficient mice. Thymus dependence and responsiveness to anti-CD3 epsilon antibody.
Thymocytes of mice deficient in the recombinase-activating gene (RAG)-1 or RAG-2 cannot express and receive signals through the pre-TCR. As a result, thymocyte development in these mice terminates at the CD4/8 double negative (DN), IL-2R-alpha-positive stage. Nevertheless, RAG-deficient DN thymocytes express functional CD3 complexes and can therefore be induced by anti-CD3 epsilon mAb to mature to the CD4+8+ double positive stage. In the present paper we demonstrate that the peripheral lymphoid organs (lymph nodes, spleen) and peripheral blood of RAG-deficient mice harbor an immature T cell population which, similar to RAG-deficient DN thymocytes, contains high levels of cytoplasmic CD3 epsilon and responds to anti-CD3 epsilon mAb in vivo. With respect to surface phenotype (Thy1.2+, PgP-1+, HSA+, Fc gamma RII/III-, IL-2R-alpha-, c-kit-), these cells are similar to intermediate stage RAG-deficient DN thymocytes. Moreover, they express mRNA for pre-TCR-alpha and for the nondeleted RAG. Following injection of anti-CD3 epsilon mAb, these cells proliferate, down-regulate heat stable Ag and PgP-1, and partially differentiate to CD4+ and CD8+ double positive and single positive cells. The induced population displays a mixed phenotype, between that of immature thymocytes and lymph node T cells in normal mice. Induction is successful in thymectomized RAG-deficient mice, suggesting that it occurs in the periphery. However, after thymectomy, inducible cells disappear with an approximate half-life of 10 to 14 days. We suggest that DN thymocytes can emigrate and repopulate peripheral lymphoid organs of RAG-deficient mice. These cells respond to CD3 signaling by aberrant maturation, possibly due to the inappropriate microenvironment of peripheral lymphoid organs.
Falk
I
I
Max-Planck Institute for Immunobiology, Freiburg, Germany.
Potocnik
A J
AJ
Barthlott
T
T
Levelt
C N
CN
Eichmann
K
K
D000818:Animals; D017252:CD3 Complex / Q000502:physiology*; D002454:Cell Differentiation; D005434:Flow Cytometry; D015329:Gene Rearrangement, T-Lymphocyte; D016654:Genes, RAG-1; D008198:Lymph Nodes / Q000166:cytology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology; D013950:Thymus Gland / Q000166:cytology*
D017252:CD3 Complex