Lyt 1+23- cells appear in the thymus before Lyt 123+ cells

Most thymocytes are either immature or functionally deficient and express a series of lymphocyte cell-surface antigen markers designated Lyt 1, Lyt 2 and Lyt 3 (refs 1, 2) which have been useful in distinguishing functional subsets of T cells. In contrast, a small population of cortisone-resistant thymocytes (CRT), confined to the thymic medulla after acute corticosteroid treatment are functionally more mature. These cells, like peripheral T cells, have restricted expression of Lyt antigens and mostly are either Lyt 1 or Lyt 123 cells. It has thus been assumed that all thymocytes initially are Lyt 1+, 2+, 3+ and by differentiation lose either Lyt 1 or Lyt 2, 3 to result in Lyt 1+(23-) and Lyt (1-)23+ cells. Using immunofluorescence (IF) and flow microfluorometry (FMF) analyses to detect Lyt antigen expression quantitatively without the requirement for cell lysis, we have now re-examined the expression of Lyt 1, 2 and 3 antigens on murine fetal thymocytes from 14 to 19 days of gestation and on normal thymocytes from birth to 2-3-month-old adults. These studies demonstrate that cells with the Lyt 1+23- phenotype first appear in the thymus several days before Lyt 123+ thymocytes are detected, and suggest either a micro-environmental or site-specific influence for phenotypic differentiation and/or two independent, pre-committed lineages.

Fc (IgG) receptors on rat basophilic leukemia cells

Receptors for IgG and IgE on rat basophilic leukemia cells (the 2H3 subline of RBL-IV) were detected by their ability bind IgE and IgG in fluorescence or radioactive assays. The 2H3 cells have approximately two-thirds as many receptors for IgG as for IgE. The IgE receptors bind monomeric IgE with high affinity and IgE binding is uninhibited by high concentrations of monomeric or oligomeric IgG. In contrast, the IgG receptors bind both (rabbit and rat) IgG and (rat) IgE. The affinity of IgG receptors for monomeric IgG and IgE is much lower than that of the IgE receptor for its ligand; binding of radiolabeled IgG or IgE to IgG receptors can be detected only with cross-linked oligomers. Although both receptors are sensitive to tryptic digestion than IgE receptors. Dual laser flow microfluorometric studies revealed that the numbers of IgG and IgE receptors per cell varied considerably among 2H3 cells and that the distributions of the 2 types of receptors were independent of each other. 2H3 cells released histamine through an IgE-mediated system, but cross-linked IgG, even in saturating amounts, did not elicit histamine release, nor have any effect upon IgE-induced release. Moreover, 2H3 cells would not mediate ADCC of IgG-coated chicken red blood cells.

Fc (IgG) receptor distributions in homogeneous and heterogeneous cell populations by flow microfluorometry

A flow microfluorometric method has been developed for quantitating the numbers of Fc receptors on individual cells. The cells were equilibrated at 0 degrees C with radiolabeled, affinity-crosslinked rabbit IgG dimers, washed, and treated with fluorescent antibodies against rabbit IgG. The stained cells were analyzed for fluorescence emission by using a fluorescence-activated cell sorter and for bound dimer molecules by using a gamma counter. Standard curves relating fluorescence emission to numbers of dimer molecules bound to cells were used to determine Fc receptor distributions on P388D1 cells, human peripheral blood lymphocytes, and normal mouse spleen cells. Essentially all of the P388D1 cells bore Fc receptors, distributed in a skewed Gaussian profile having a peak at 2 X 10(5) receptors per cell. Human peripheral blood lymphocytes and mouse spleen cells contained positive and negative subpopulations. The percentage of positive cells in human lymphocytes from different donors ranged from 50 to 25; the receptor distributions of these cells were symmetrical and similar in all donors in shape and average receptor density (4.2 X 10(4) receptors per cell). Mouse spleen cells contained 55% positive cells with nonsymmetrical heterogeneous distributions of receptor densities. These cells peaked at 1 to 2 X 10(4) receptors per cell, but significant numbers of cells had receptor densities 10- to 20-fold greater.

Fc (IgG) receptors on rat basophilic leukemia cells

Receptors for IgG and IgE on rat basophilic leukemia cells (the 2H3 subline of RBL-IV) were detected by their ability bind IgE and IgG in fluorescence or radioactive assays. The 2H3 cells have approximately two-thirds as many receptors for IgG as for IgE. The IgE receptors bind monomeric IgE with high affinity and IgE binding is uninhibited by high concentrations of monomeric or oligomeric IgG. In contrast, the IgG receptors bind both (rabbit and rat) IgG and (rat) IgE. The affinity of IgG receptors for monomeric IgG and IgE is much lower than that of the IgE receptor for its ligand; binding of radiolabeled IgG or IgE to IgG receptors can be detected only with cross-linked oligomers. Although both receptors are sensitive to tryptic digestion than IgE receptors. Dual laser flow microfluorometric studies revealed that the numbers of IgG and IgE receptors per cell varied considerably among 2H3 cells and that the distributions of the 2 types of receptors were independent of each other. 2H3 cells released histamine through an IgE-mediated system, but cross-linked IgG, even in saturating amounts, did not elicit histamine release, nor have any effect upon IgE-induced release. Moreover, 2H3 cells would not mediate ADCC of IgG-coated chicken red blood cells.

Preparative separation of human T cells reactive with the OKT4 monoclonal antibody

A cell separation technique is described which can provide large numbers (i.e. greater than 5 x 10(7)) of human lymphoid cells which are positively and negatively selected for their ability to react with the OKT4 monoclonal antibody. Peripheral blood lymphocytes are depleted of plastic-adherent cells and then exposed to OKT4 antibody. Unbound OKT4 antibody is removed by washing and then this OKT4-exposed cell population is placed on plastic Petri dishes that are coated with affinity-purified goat anti-mouse immunoglobulin. Cells which do not bind the OKT4 antibody (OKT4- cells) can be obtained by gently washing the nonadherent cells from the plates, while the adherent (OKT4+) cells can be recovered by vigorous pipetting. This procedure yields functional OKT4+ and OKT4- cell populations with a purity which approaches that obtained by separation using the fluorescence-activated cell sorter. The principal advantages of this plate separation technique are that: (1) large numbers of functional cell populations can be obtained; (2) very small quantities of monoclonal antibody (e.g. 1:10(4) dilution of ascites) are required; and (3) sterility of the cell preparations can be maintained quite easily.

Ly 9, an alloantigenic marker of lymphocyte differentiation

A new lymphocyte cell surface alloantigen, provisionally designated Ly 9, is detected by flow microfluorometry(FMF), as an extra specificity in sera from anti-Lyt immunizations. Ly 9.2, one of the allelic specificities, commonly is detected as a unique immunofluorescence profile of thymocytes with anti-Lyt 3.1 sera. The alternative antigenic specificity, Ly 9.1, can be detected routinely in antisera prepared against Lyt 2.1 and Lyt 3.2. This lymphocyte alloantigen has both a unique strain and cell/tissue distribution. Quantitative measurement of Ly 9 immunofluorescence by FMF on heterozygote cells shows that Ly 9 antigen expression is co-dominant and reduced in levels relative to parental homozygote cells. Ly 9 is expressed on all thymocytes, peripheral lymphocytes, and on a subpopulation of cells in the bone marrow. This antigen is not expressed to any significant degree on erythrocytes, epidermal cells, sperm, or in suspensions of testis, brain, kidney, liver, or lung. FMF analysis and absorption typing reveals a quantitatively lower level of antigen expression on thymocytes compared with spleen or lymph node cells. Cytotoxic elimination experiments confirm that Ly 9 is expressed on at least 2 different T cell functional subsets and B cells.

Phenotypic expression of I-A and I-E/C subregion determinants on murine thymocytes

The expression of Ia antigens on murine thymocytes has been assessed by indirect immunofluorescence and flow microfluorometry analysis. Antisera specific for I-region determinants were found to react with at least 50% of thymus cells in single-cell suspensions. When these antisera were tested on thymus cells of an appropriate recombinant strain, it was found that both I-A and I-E/C subregion determinants could be detected. Monoclonal antibodies to I-A and to I-E determinants also reacted with thymus cells in a similar fashion, eliminating the possibility that contaminating specificities accounted for the reactivity of alloantisera. The majority of Ia-positive thymus cells appeared to express determinants encoded by genes of both I-A and I-E/C subregions. Ia expression on individual thymocytes was also correlated with cell size as measured by forward light scatter intensity. However, unlike antigens detected by rabbit anti-mouse brain antisera, Ia antigens did not appear to be associated with known subpopulations of thymocytes distinguishable by light scatter intensity. The presence of I-region encoded antigens on thymocytes may play a role in maturation of T cells in the thymus microenvironment.

Phenotypic expression of I-A and I-E/C subregion determinants on murine thymocytes

The expression of Ia antigens on murine thymocytes has been assessed by indirect immunofluorescence and flow microfluorometry analysis. Antisera specific for I-region determinants were found to react with at least 50% of thymus cells in single-cell suspensions. When these antisera were tested on thymus cells of an appropriate recombinant strain, it was found that both I-A and I-E/C subregion determinants could be detected. Monoclonal antibodies to I-A and to I-E determinants also reacted with thymus cells in a similar fashion, eliminating the possibility that contaminating specificities accounted for the reactivity of alloantisera. The majority of Ia-positive thymus cells appeared to express determinants encoded by genes of both I-A and I-E/C subregions. Ia expression on individual thymocytes was also correlated with cell size as measured by forward light scatter intensity. However, unlike antigens detected by rabbit anti-mouse brain antisera, Ia antigens did not appear to be associated with known subpopulations of thymocytes distinguishable by light scatter intensity. The presence of I-region encoded antigens on thymocytes may play a role in maturation of T cells in the thymus microenvironment.

Ly 9, an alloantigenic marker of lymphocyte differentiation

A new lymphocyte cell surface alloantigen, provisionally designated Ly 9, is detected by flow microfluorometry(FMF), as an extra specificity in sera from anti-Lyt immunizations. Ly 9.2, one of the allelic specificities, commonly is detected as a unique immunofluorescence profile of thymocytes with anti-Lyt 3.1 sera. The alternative antigenic specificity, Ly 9.1, can be detected routinely in antisera prepared against Lyt 2.1 and Lyt 3.2. This lymphocyte alloantigen has both a unique strain and cell/tissue distribution. Quantitative measurement of Ly 9 immunofluorescence by FMF on heterozygote cells shows that Ly 9 antigen expression is co-dominant and reduced in levels relative to parental homozygote cells. Ly 9 is expressed on all thymocytes, peripheral lymphocytes, and on a subpopulation of cells in the bone marrow. This antigen is not expressed to any significant degree on erythrocytes, epidermal cells, sperm, or in suspensions of testis, brain, kidney, liver, or lung. FMF analysis and absorption typing reveals a quantitatively lower level of antigen expression on thymocytes compared with spleen or lymph node cells. Cytotoxic elimination experiments confirm that Ly 9 is expressed on at least 2 different T cell functional subsets and B cells.

HLA-DRw alloantigens can be detected on peripheral blood T lymphocytes

Antisera detecting HLA-DRw antigens (human Ia-like) react in cytotoxicity assays with peripheral blood B cells and monocytes but not T lymphocytes. Antisera detecting DRw specificities were used in flow microfluorometry studies to determine whether T lymphocytes express these antigens in quantities not detected by cytotoxicity. Peripheral blood lymphocytes depleted of monocytes were incubated with DRw antisera, reacted with fluoresceinated goat anti-human IgG, and analyzed on the fluorescence-activated cell sorter (FACS). Anti-DRw sera were found to be reactive on all of the lymphocytes as evidenced by a positive fluorescence signal. The reactivity was specific in that only those sera that detected DRw antigens on B cells and monocytes were reactive with the total lymphocyte population from the same donor. Reactivity of the antisera was removed by absorbing the antiserum with monocyte/B cells and T cells from a donor with the same DRw antigen as that found on the target cell of the donor tested. The results demonstrate the presence of DRw antigens on resting peripheral blood T lymphocytes. The implications of quantitative differences in DRw antigen expression on lymphoid cells are discussed.

HLA-DRw alloantigens can be detected on peripheral blood T lymphocytes

Antisera detecting HLA-DRw antigens (human Ia-like) react in cytotoxicity assays with peripheral blood B cells and monocytes but not T lymphocytes. Antisera detecting DRw specificities were used in flow microfluorometry studies to determine whether T lymphocytes express these antigens in quantities not detected by cytotoxicity. Peripheral blood lymphocytes depleted of monocytes were incubated with DRw antisera, reacted with fluoresceinated goat anti-human IgG, and analyzed on the fluorescence-activated cell sorter (FACS). Anti-DRw sera were found to be reactive on all of the lymphocytes as evidenced by a positive fluorescence signal. The reactivity was specific in that only those sera that detected DRw antigens on B cells and monocytes were reactive with the total lymphocyte population from the same donor. Reactivity of the antisera was removed by absorbing the antiserum with monocyte/B cells and T cells from a donor with the same DRw antigen as that found on the target cell of the donor tested. The results demonstrate the presence of DRw antigens on resting peripheral blood T lymphocytes. The implications of quantitative differences in DRw antigen expression on lymphoid cells are discussed.

Differential binding of fluorescein-labeled lectins to mouse thymocytes: subsets revealed by flow microfluorometry

Fluorescein-labeled lectins bound to mouse thymocytes were analyzed by flow microfluorometry. This technique has identified several lectins that bind differentially to thymocyte subsets. The most complex fluorescence distributions were obtained using lectins with nominal specificities for galactose or N-acetylglucosamine. Inhibition of binding by sugars confirmed that the fluoresceinated lectins were bound to cells at their carbohydrate binding site. Simultaneous analyses of lectin fluorescence and forward light scatter intensity showed that cell subpopulations of different sizes can exhibit marked differences in the level of binding such that the amount of lectin bound per cell is often independent of cell size. A minor population of dull or unstained cells, delineated by several of these lectins, correlates with the subpopulation of medium-sized thymocytes resistant to in vivo cortisone treatment.

Differential binding of fluorescein-labeled lectins to mouse thymocytes: subsets revealed by flow microfluorometry

Fluorescein-labeled lectins bound to mouse thymocytes were analyzed by flow microfluorometry. This technique has identified several lectins that bind differentially to thymocyte subsets. The most complex fluorescence distributions were obtained using lectins with nominal specificities for galactose or N-acetylglucosamine. Inhibition of binding by sugars confirmed that the fluoresceinated lectins were bound to cells at their carbohydrate binding site. Simultaneous analyses of lectin fluorescence and forward light scatter intensity showed that cell subpopulations of different sizes can exhibit marked differences in the level of binding such that the amount of lectin bound per cell is often independent of cell size. A minor population of dull or unstained cells, delineated by several of these lectins, correlates with the subpopulation of medium-sized thymocytes resistant to in vivo cortisone treatment.

Lysophosphatidylcholine in liposomal membranes: enhanced permeability but little effect on transfer of a water-soluble fluorescent marker into human lymphocytes

In an attempt to enhance delivery of liposome contents into cells, we tested the effect of lysophosphatidylcholine on transfer of the fluorescent dye, carboxyfluorescein, from small unilamellar and large multilamellar vesicles to human lymphocytes. Dioleoyl phosphatidylcholine and dioleoyl phosphatidylcholine-lysophosphatidylcholine small unilamellar vesicles with varying lipid ratios were prepared and characterized. In the presence of lysophosphatidylcholine, small unilamellar vesicles were slightly smaller and more leaky than those made without lysophosphatidylcholine. Lysophosphatidylcholine induced less leakage in large multilamellar vesicles. It did not show any appreciable effect on transfer of liposome contents, whether included as part of the liposomal bilayer (of unilamellar or multilamellar vesicles) or added exogenously together with small unilamellar dioleoyl phosphatidylcholine vesicles.

Role of accessory cells in B cell activation. I. Macrophage presentation of TNP-Ficoll: evidence for macrophage-B cell interaction

The importance of cell interaction for thymic independent antigen responses has not been widely appreciated. The present report demonstrates, however, that macrophage-B cell interaction may be an important feature of B ce-l activation for the response to at least one polysaccharide thymic independent antigen, TNP-Ficoll. Experiments were performed demonstrating that a strict accessory cell requirement exists for the thymic independent response to soluble TNP-Ficoll, and that such accessory cells are both adherent and phagocytic, that is, macrophages. It was further demonstrated that macrophages could be pulsed with TNP-Ficoll and that these pulsed macrophages could activate B cells to respond, but only if the pulsed macrophages were viable. Thus, one function that macrophages can fulfill in responses to TNP-Ficoll is the specific function of antigen presentation. Such presentation of TNP-Ficoll by macrophages to B cells suggests that the antigen may not be activating B cells directly, and raises the possibility that the interaction of B cells and macrophages might be genetically restricted.

Role of accessory cells in B cell activation. I. Macrophage presentation of TNP-Ficoll: evidence for macrophage-B cell interaction

The importance of cell interaction for thymic independent antigen responses has not been widely appreciated. The present report demonstrates, however, that macrophage-B cell interaction may be an important feature of B ce-l activation for the response to at least one polysaccharide thymic independent antigen, TNP-Ficoll. Experiments were performed demonstrating that a strict accessory cell requirement exists for the thymic independent response to soluble TNP-Ficoll, and that such accessory cells are both adherent and phagocytic, that is, macrophages. It was further demonstrated that macrophages could be pulsed with TNP-Ficoll and that these pulsed macrophages could activate B cells to respond, but only if the pulsed macrophages were viable. Thus, one function that macrophages can fulfill in responses to TNP-Ficoll is the specific function of antigen presentation. Such presentation of TNP-Ficoll by macrophages to B cells suggests that the antigen may not be activating B cells directly, and raises the possibility that the interaction of B cells and macrophages might be genetically restricted.

Identification and separation of Thy-1 positive mouse spleen cells active in natural cytotoxicity and antibody-dependent cell-mediated cytotoxicity

The expression of the Thy-1 antigen on mouse spleen cells responsible for NK activity and ADCC was investigated by using a monoclonal IgM anti-Thy-1.2 antibody. Both C-mediated cytotoxicity and the fluorescence-activated cell sorter were used to fractionate cells. The effector cells were found to be heterogeneous in their expression of Thy-1. Effector cells from nude BALB/c mice were predominantly Thy-1 positive; some of the NK cells in CBA spleens appeared to be Thy-1 positive, but at least one-third of the lytic activity was due to Thy-1 negative cells. The effects of treatments on NK cytotoxicity and ADCC were very similar, supporting the hypothesis that the same cells mediate both activities.

Variations in expression of xenotropic murine leukemia virus genomes in lymphoid tissues of NZB mice

Lymphocytes from Thy, Sp, LN, and BM and NZB mice were tested for expression of X-MuLV genomes as cell surface gp70 (XenCSA) or infectious virus. The results demonstrate major dissociations for these parameters of X-MuLV expression in different lymphoid compartments and suggest that factors involved in T lymphocyte differentiation modify the levels of expression in these two modes.

Expression of xenotropic murine leukemia viruses as cell-surface gp70 in genetic crosses between strains DBA/2 and C57BL/6

Flow microfluorometry was used to assess levels of xenotropic murine leukemia virus envelope-related cell-surface antigens (XenCSA) expressed on lymphocytes of mice derived from crosses between C57BL/6 (B6) and DBA/2 (D2); 24 recombinant inbred strains (BXD RIs) and 62 backcross mice were studied. The results suggest that XenCSA expression is affected by more than one gene but that the predominant influence is exerted by a single semidominant gene apparently located on chromosome 4 at or in close proximity to the Fv-1 locus. Studies of spontaneous virus production in B6D2F1 X D2 mice suggest that this locus may also affect production by spleen cells of xenotropic MuLV registering in a fluorescent antibody assay of mink lung cells.

Phenotypic and functional effects of the motheaten gene on murine B and T lymphocytes

Lymphoid cells from C57BL/6 mice homozygous for the me gene exhibit multiple phenotypic and functional abnormalities from early as one week of age. In the B cell population these include a reduction in the frequency of detectable surface Ig+ cells, alterations in the level of expression of surface IgM and IgD, an increase in the frequency of large cells, plasma cells and TNP-specific plaque forming cePS. Together these findings provide strong evidence for polyclonal activation of B cells. The high level of expression of xenotropic MuLV gp70 by me/me spleen and lymph node cells provides further evidence for lymphoid cell activation. In preliminary studies, me/me T cells appeared to be phenotypically and functionally less affected by the me gene. The distribution of Thy 1.2 on the surface of spleen and lymph node T cells varied from low to normal and the mitogenic responses to Con A and PHA were depressed. It remains to be determined what the basic deficiency in me/me mice is and whether it affects primarily B cells or all lymphoid cells.