Differential response of B and T cells to ALS revealed by electrophoretic mobility determinations

Alternative pathway activation of T cells by binding of CD2 to its cell-surface ligand

Activation of resting T lymphocytes is initiated by the interaction of cell-surface receptors with their corresponding ligands. In addition to activation through the CD3 (T3)-Ti antigen-receptor complex, recent experiments have demonstrated induction of T-cell proliferation through the CD2 (T11) molecule, traditionally known as the erythrocyte(E)-receptor, through which T cells can bind red blood cells (RBC). This 'alternative pathway' of T-cell activation was observed in vitro in response to combinations of anti-CD2 monoclonal antibodies (mAbs) that bind to distinct epitopes of CD2, such as mAbs against T11(2) plus T11(3). The physiological importance of this activation pathway can be assessed only by studying the effects of a naturally occurring ligand of CD2 on T-cell activation. We have recently described such a ligand, a glycoprotein of apparent relative molecular mass 42,000 (Mr 42K) that is expressed on all blood cells and some other tissues. Here we demonstrate that binding of this cell surface molecule, termed T11 target structure or T11TS, to CD2 (T11) induces reactivity in resting T cells to a mitogenic stimulus given by a mAb to the T11(3) determinant or by submitogenic concentrations of anti-T11(2+3) mAbs. Thus, one of the signals required for T-cell activation through the alternative pathway is provided by the interaction of CD2 with a naturally occurring complementary cell-surface molecule.

The role of accessory cells in polyclonal T cell activation II. Induction of interleukin 2 responsiveness requires cell-cell contact

It has previously been reported (Hünig, T. et al., Eur. J. Immunol. 1983. 13:1) that highly purified peripheral T cells do not respond to concanavalin A (Con A) even in the presence of Con A-induced spleen cell supernatant as a source of interleukin 2 (IL 2). In the present report, the hypothesis was tested whether this unresponsiveness correlates with the observed inability of Con A to mediate cell-cell contact between highly purified T cells. It was found that T cells, pretreated with neuraminidase to reduce their net negative charge, were both aggregated and rendered IL 2-reactive by Con A. In addition, leukoagglutinin (LA) was found to be able to both agglutinate untreated T cells and to make them IL 2-reactive. Neuraminidase treatment reduced the concentration of LA required to mediate both effects. Neuraminidase treatment did not alter the overall Con A-binding capacity of T cells, nor did it induce reactivity to IL 2 in the absence of lectin. Furthermore, irradiated, neuraminidase-treated T cells served as accessory cells (AC) in the induction of responsiveness to IL 2, but not for production of IL2, which depends on Ia+ AC. Finally, Lyt-2- neuraminidase-treated peripheral T cells responded in the same fashion as whole T cell populations, indicating that at least some T cells of the helper phenotype need not interact with Ia+AC for the induction of IL 2 responsiveness.

Antigen-specific electrophoretic cell separation (ASECS): isolation by human T and B lymphocyte subpopulations by free-flow electrophoresis after reaction with antibodies

The electrophoretic mobility of human lymphocytes can be reduced by incubation with surface antigen specific antibodies under non-capping conditions. This renders subpopulations of human peripheral blood lymphocytes accessible to separation by free-flow electrophoresis. After reaction of lymphocyte preparations with anti-IgM antibody and a fluorescent second antibody, B lymphocytes showed a considerable shift in position in preparative cell electrophoresis and could be separated with high yield, purity and vitality. Similarly, a T cell subpopulation reactive with the monoclonal antibody T811 could be isolated, even though only small amounts of this antibody were bound, by using a double-sandwich method. Non-specific antibody uptake via Fc-receptors did not contribute to the observed shift of antibody-labelled cells to lower electrophoretic mobility. Flow cytometric analysis showed that cells were separated according to their antigen density. Thus cell electrophoresis can be used to separate antibody-labelled cells. With a flow rate of 100,000 cells/sec this method has a much higher separation capacity than fluorescence-activated cell sorting. The described method should be applicable to the separation of a wide range of cell populations for which specific antibodies are available.

The effect of anti-lymphocyte serum, mitogens and enzymatic treatment on the agglutination and surface charge of lymphoid cells

Agglutination of thymocytes and B-cells with anti-lymphocyte serum subsequent to treatment of the cells with trypsin or neuraminidase was slightly and similarly increased, independent of the effect on the surface charge shown previously. The enzymatic treatment did not increase capping of antiserum binding sites. Agglutination caused by binding of IgG antibodies of anti-lymphocyte serum was not accompanied by change in the net surface charge. Neither did binding of the mitogens phytohaemagglutinin, concanavalin A or poke-weed mitogen influence the surface charge of the cells.

Thymus-dependent and thymus-independent lymphocyte separation: relation to exposed sialic acid on cell surface

On preparative cell electrophoresis mouse lymph node lymphocytes separate into fast-moving (T, thymus-dependent) and slow-moving (B, thymus-independent) fractions. After treatment with neuraminidase all lymphocytes move as one very slow fraction, indicating that the difference in the mobility of the two kinds of cells is due to differences in the density of exposed sialic acid on their surfaces.