Flow cytometry as an analytic and preparative tool for studies of neuroendocrine function.
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Biomedical subjects
J G Monroe
Publications and source records attributed to J G Monroe.
B cell activation. II. Receptor cross-linking by thymus-independent and thymus-dependent antigens induces a rapid decrease in the plasma membrane potential of antigen-binding B lymphocytes.
We report the specific induction of B cell plasma membrane depolarization with the use of thymus-dependent and -independent antigens. We have utilized various trinitrophenol-carrier conjugates for the stimulation of isolated trinitrophenol-binding mouse B cells. Membrane depolarization was assessed by flow cytometric analysis of 3-3'-pentyloxacarbocyanine iodide (DiOC5[3])-stained cells. Entry into the cell cycle was determined by flow cytometric analysis of acridine orange-stained cells. The results indicate that polyvalent antigens, but not free hapten, induce B cell membrane depolarization by a large proportion of antigen-binding cells within 2 hr of stimulation. Although all polyvalent antigens induce membrane depolarization, only thymus-independent antigens induce the subsequent G0 to G1 transition, suggesting that the membrane Ig cross-linking signal alone, although sufficient to induce membrane depolarization and subsequent increased IA expression, is insufficient to drive the entry of B cells into the cell cycle. The G0 to G1 transition appears to be dependent on a second signal, perhaps mediated by the thymus-independent carrier or antigen-specific, Ia-restricted T cell helper.
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Level of mIa expression on mitogen-stimulated murine B lymphocytes is dependent on position in cell cycle.
Using correlated flow cytometric analysis of cell surface Ia antigen expression (immunofluorescence) and cell cycle phase (pulse-width of axial light extinction), we have quantitated changes in expression of mIa antigen on murine B cells during progression through cell cycle. Our results indicate that density of mIa expressed on mitogen-stimulated B cells increases fourfold to fivefold during the transition from G0 to G1. By early S phase, mIa density has decreased by fourfold to fivefold relative to peak expression. This decrease becomes more evident by late S, G2, and M phases, when an eightfold decrease in mIa antigen density is observed relative to peak levels. This decrease results in mIa antigen expression lower than that of resting, unstimulated B cells. Therefore, maximum mIa antigen expression occurs during G0 to G1 transition and in early G1, when a requirement for I region-restricted, antigen-driven T cell help for thymus-dependent, antigen-driven B cell activation has been demonstrated.
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Definition of conditions that enable antigen-specific activation of the majority of isolated trinitrophenol-binding B cells.
In an effort to further elucidate the early cellular events in generation of antibody responses, we have determined the requirements for antigen-specific initiation of the G0 to G1 transition by isolated trinitrophenol (TNP) -binding B lymphocytes. TNP-binding cells were isolated from normal B6D2F1 splenocyte populations using hapten affinity fractionation on disulfide-bonded TNP-gelatin-coated plates. Populations prepared in this way are greater than or equal to 96% immunoglobulin positive and 70-95% antigen binding. Isolated cells were cultured for 48 h in the presence of a variety of TNP conjugates including TNP-Brucella abortus (Ba), TNP-Ficoll, TNP-sheep erythrocytes (SRBC), TNP-human gamma globulin (HGG), or TNP-ovalbumin (OVA) before being harvested and subjected to acridine orange cell cycle analysis. As many as 80% of cells were in cycle by 48 h in response to TNP-Ba, a thymus-independent (TI1 antigen. A smaller proportion (congruent to 40%) were in cycle in response to TNP-Ficoll, a TI2 antigen. Significant activation was not detected in cultures challenged with the thymus-dependent immunogens TNP-SRBC, TNP-HGG, and TNP-OVA. Addition of interleukin 1 (IL-1), IL-2, B cell growth factor, and/or T cell-replacing factor to cultures did not facilitate responses to these immunogens, suggesting a requirement for antigen-specific T cell help for entry into cell cycle induced by thymus dependent antigens. Activation by TNP-Ba was antigen specific and independent of accessory cells, occurring with equal efficiency in bulk and single-cell cultures. Activation by TNP-Ba was inhibitable by anti-Fab and anti-mu antibodies, but not by anti-delta antibodies. Results indicate that activation of TNP-binding cells to enter cell cycle by TNP-Ba is independent of accessory cells and requires interaction of antigen with cell surface IgM. Exposure to thymus-dependent TNP-immunogens plus nonspecific helper factors is insufficient to cause entry of TNP-binding cells into cycle.
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Enrichment of viable lymphocytes in defined cycle phases by sorting on the basis of pulse width of axial light extinction.
A correlation between cell size and cycle state is demonstrated for mitogen stimulated murine lymphocytes. Cell cycle analysis was performed using multiparameter cytofluorometric analysis of acridine orange stained cells. Cell size was determined by measuring "time of flight" of axial light extinction. Cells with diameters of 5.0 - 6.0 micron are shown to be predominately in G0. Among stimulated cells, those 6.0 - 7.0 micron in diameter are predominately early and late G1 (80%) with some S phase cells. Cells in G2 + M were found to predominate among lymphocytes with diameters of 7.5 - 12 micron. This approach provides a method for isolation of lymphocytes in specific phases of the cell cycle which are suitable for subsequent functional studies.
Acridine Orange↗
Cell cycle dependence for expression of membrane associated IgD, IgM and Ia antigen on mitogen-stimulated murine B-lymphocytes.
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Genetically restricted antigen presentation for immunological tolerance and suppression.
The activation of some subsets of T cells requires the recognition of antigen in association with self Ia determinants. It is not clear, however, whether this is also necessary for the induction of unresponsiveness and the active suppression of hapten-specific T cells. We have studied the regulation of the delayed-type hypersensitivity (DTH) response in mice. Subcutaneous (s.c.) injection of haptenated syngeneic cells primarily activates T helper cells, while intravenous (i.v.) injection results in unresponsiveness and the activation of T suppressor cells. Presentation of antigen by an I-A-positive antigen-presenting cell (APC) seems to be critical for T helper cell activation. We now show that the activation of first-order T suppressor cells requires the presentation of hapten on an I-J-positive APC. However, i.v. injection of I-J-depleted haptenated cells also results in hepten-specific unresponsiveness. This non-transferable T-cell tolerance requires the presence of an I-A-positive APC and is genetically restricted. These results suggest that distinct modes of antigen presentation and administration are required for immunity, suppression and non-transferable tolerance.
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