Characterization of CD4+ T cells in mouse bone marrow. I. Increased activated/memory phenotype and altered TCR Vbeta repertoire.
A significant proportion of memory B cells home to bone marrow (BM) which is a major site of anamnestic antibody responses in mice. We hypothesized that memory T cells likewise accumulate in BM perhaps to provide help for antibody production, and that the compartment of CD4+ T cells in BM of unimmunized mice would be enriched for memory phenotype cells that might have been activated by environmental antigens. The phenotype of activated/memory CD4+ lymphocytes has been defined as CD44hi CD45RBlo CD62L-. Conversely, the phenotype of immunologically naive cells is CD44lo CD45RBhi CD62L+. Flow cytrometric analysis of tissue from normal, adult C57BL/6 mice identified 1-2 % CD3+CD4+ cells in BM. Up to 40 % of CD3+CD4+ cells in the BM expressed the activated/memory phenotype compared with < or = 10% in the spleen and lymph nodes. Analysis of TCR Vbeta repertoire revealed that expression of Vbeta3 and Vbeta7 genes was increased as much as fourfold in BM compared to the periphery; most of this increase was within the CD44hi T cells. The accumulation of activated/memory T cells and clonotypic expansion(s) was not seen in the BM of germ-free mice, indicating that it reflects the history of the animal's exposure to antigens. Finally, immunization of mice which express a transgenic T cell receptor specific for ovalbumin peptide resulted in appearance of antigen-specific T cells with activated/memory phenotype in the BM.
Price
P W
PW
Department of Microbiology and Immunology, University of Maryland, Baltimore 21201, USA.
Cerny
J
J
D000818:Animals; D001854:Bone Marrow Cells / Q000145:classification / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000145:classification / Q000276:immunology*; D005260:Female; D007135:Immunoglobulin Variable Region / Q000276:immunology*; D007156:Immunologic Memory; D016130:Immunophenotyping; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology*
D007135:Immunoglobulin Variable Region; D016693:Receptors, Antigen, T-Cell, alpha-beta