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Functionally defined mouse Lyt-1 and Lyt-2 cell sets were selected from peripheral lymph nodes by cytotoxic elimination with anti-Lyt monoclonal antibodies. The selected populations were labeled with 51Cr or [3H]-adenosine and traced in syngeneic recipients at 1, 24, 45 and 65 hr after intravenous injection. Recovered radioactivity in recipient organs was measured by gamma-counting. The exact tissue positioning of the labelled cells was determined by autoradiography and labelled cell counting in spleen, lymph node and Peyer's patch microenvironments. Selected cell sets differed from unselected T cells in two ways: (i) Selected Lyt-1 and Lyt-2 cells showed some decline in recovery from recipient lymph nodes at 24 hr after injection; (ii) Lyt-2 cells showed enhanced localization to Peyer's patches. Autoradiographic analysis of microenvironmental tissue positioning of [3H]-adenosine labeled cells confirmed a relatively higher localization of Lyt-2 cells in Peyer's patches than in lymph nodes. In both tissues, the majority of the labeled cells were found in T areas. In the spleen, a higher proportion of Lyt-2 cells was seen in T-independent follicular areas. [ABSTRACT FROM AUTHOR]

The effect of anti-Lyt-1 monoclonal anti-body treatment on the in vivo migration properties of mouse T lymphocytes was examined. Cells were treated with antibody in the presence or absence of complement. T cells of the Lyt-2 cytotoxic/suppressor phenotype were selected from B6 spleen cell suspensions by cytotoxic elimination with an allospecific anti-Lyt-1,2 antibody. These cells were labeled with 51Cr and transferred to syngeneic recipients which were killed 1 or 24 hr later for assessment of radiolabel tissue distribution. In vivo migration of anti-Lyt-1.2 selected cells was similar to that of unselected T cells. By contrast, a functionally and phenotypically identical population selected from C3H spleen T cells with an anti-Lyt-1.1 monoclonal antibody showed increased accumulation in recipient liver and a decline in recovery from lymph nodes and spleen. Treatment with anti-Lyt-1.1 in the absence of complement caused even greater localization to the liver, with a simultaneous poor recovery from lymphoid tissues; similar treatment of cells from B6 Lyt-1.1 congenic mice also resulted in altered migration. Treatment of B6 lymphocytes with anti-Lyt-1.2 in the absence of complement caused little change in the normal T cell tissue localization. These results suggest that selected Lyt-2 cells, reported to express low levels of Lyt-1 antigen undetectable by conventional u.v. light microscopy immunofluorescence and serological methods, may contain residual bound antibody which can result in opsonization and sequestration of the cells by recipient stromal cells after in vivo transfer. Binding of the antibody directed to the Lyt-1.2 allospecificity of B6, although of the same immunoglobulin class and selecting for a similar functional set by cytotoxic elimination, does not cause such sequestration in vivo. [ABSTRACT FROM AUTHOR]

Spleen cells from BN rats were separated in a discontinuous density gradient. Cells from different fractions were shown to be functionally diverse, light cells enhancing DNA synthesis and cell division of the dense cell fractions, while dense cells suppressed DNA synthesis and cell division of light cells. Both these effects were also present in the absence of cell stimulation, were proportional to the number of modulating cells added to the cultures, and totally independent of the magnitude of response of controls. In Con A-stimulated cultures, mitogen dose also influenced the intensity of help and suppression. Both these effects are blocked by cell treatment with cycloheximide and can be mediated by cell supernatants. A T cell seems to be responsible for both helper and suppressor effects. [ABSTRACT FROM AUTHOR]

Thymus was labelled in vivo by injecting newborn C3H/Bi mice with three or four doses of 2 μc of [3H]thymidine. The labelled thymus was grafted into the kidney capsule of 22-25-day-old intact and thymectomized syngeneic recipients which were killed 18, 41 or 42 days later. The grafts and lymphoid tissue were sectioned and examined by autoradiography after exposure times of up to 26 weeks. Small and medium labelled lymphocytes were seen in the thymus-dependent areas of the lymph nodes and spleen of all recipients provided the sections were exposed for a sufficiently long period. More labelled cells were seen in recipients killed at 18 days than at 41 or 42 days after grafting. It was concluded that these cells were the direct descendants of those cells labelled in the graft. There was no evidence of re-utilization of the isotope label. Most of the cells originally labelled in the graft either lost their label by multiple divisions or were replaced by unlabelled cells; although the epithelial-reticular cells remained heavily labelled. The importance of this last finding is discussed. [ABSTRACT FROM AUTHOR]