Direct fluorescent labeling of cells with fluorescein or rhodamine isothiocyanate. II. Potential application to studies of lymphocyte migration and maturation

The effect of direct cell labeling with fluorescein or tetramethyl rhodamine isothiocyanate on lymphocyte migration is examined. In vitro conditions of labeling are defined which (1) do not significantly affect immediate or long term viability of lymphocytes (up to 2 weeks after transfer in vivo), (2) do not alter normal lymphocyte migration, (3) do not affect expression or detectability of surface antigens, and (4) permit direct visualization and counter-staining with fluorescent antibody reagents for days after intravenous injection. The potential application of this method to studies of lymphocyte migration and maturation is discussed.

Distribution of H-2 microenvironments in the mouse thymus. Immunoelectron microscopic identification of I-A and H-2K bearing cells

Antigens coded for by the major histocompatibility complex (MHC) are differentially expressed in the mouse thymus. Immunoperoxidase studies of frozen thymus sections incubated with monoclonal (hybridoma) anti-I-Ak antibodies revealed a dendritic straining pattern in the cortex and a confluent staining pattern in the medulla. Serial sections incubated with monoclonal anti-H-2Kk antibodies showed that H-2Kk antigens were only present at detectable levels in the medulla. Microenvironments expressing H-2Kk antigens also expressed I-Ak antigens. In cortico-medullary regions, relatively large MHC-negative areas were found. These areas appeared to connect to perivascular spaces surrounding blood vessels. Using a new postfixation labeling method for the detection of cell surface associated antigens on cells of the lymphoid system in situ, we have characterized the nature of MHC positive cell types at the ultrastructural level. These studies show that epithelial-reticular cells are the major MHC positive elements in the thymus. Lymphocytes in the medulla and in cortico-medullary bounderies are also MHC positive, however, lymphocytes in the cortex were not detectably labeled. These findings support the contention that epithelial-reticular cells are involved in the H2-restriction process during T cell maturation.

Direct fluorescent labeling of cells with fluorescein or rhodamine isothiocyanate. I. Technical aspects

A rapid and simple method of cell labeling by stable conjugation with fluorescein or rhodamine is described. Viable cells are incubated under benign conditions (near physiologic pH in normal media) with free fluorescein or tetramethyl rhodamine isothiocyanate, and are adequately separated from unreacted fluorochrome by washing or centrifugation through fetal calf serum. The effects of the pH, the time and temperature of incubation, and the concentration of cells, fluorochrome, and free protein in the media are described. The method labels all cell types, although to different degrees. Fluorescence microscopy reveals fluorescence throughout the cell, although chromatin appears relatively spared. Cellular fluorescence is fairly stable at 4 and 25 degrees C, decays rapidly at 37 degrees C, but is nonetheless visible for days even at this temperature. In the case of lymphocytes, intense fluorescence is obtained without affecting cell viability, and without alteration of the ability to mount a graft versus host response.

Blocking effect of lyt-2 antibodies on T cell functions

Monoclonal anti-Lyt-2 antibodies blocked effector function of cytotoxic thymus-derived (T) cells in the absence of added complement. Cytolysis of both allogeneic cells and syngeneic lymphoma or sarcoma target cells was inhibited at the level of the effector lymphocytes. Anti-Lyt-1 and anti-Thy-1 antibodies did not block killer cells. Proliferation of T cells in mixed lymphocyte culture was also inhibited by anti-Lyt-2, but not affected by anti-Lyt-1 or anti-Thy-1 antibodies. Although Lyt-1+ lymphocytes were required in the mixed lymphocyte reaction as helper cells for proliferation of Lyt-2+ lymphocytes, their helper function was not affected by the presence of Lyt-1 antibodies. Thus, although anti-Lyt-1, anti-Lyt-2 and anti-Thy-1 were of the same gamma 2A immunoglobulin class, had high titers, and interacted with T cells to the same extent, only anti-Lyt-2 blocked T cell functions. Polyclonal activation of T lymphocytes by concanavalin A, in contrast to activation by alloantigens, was not inhibited by Lyt-2 antibodies, suggesting that Lyt-2 antibodies interfere with T cell function at the level of the T cell antigen-receptor. The role which Lyt-2 molecules may play in T cell function is discussed.

Organ specificity of lymphocyte migration: mediation by highly selective lymphocyte interaction with organ-specific determinants on high endothelial venules

Evidence is presented that the organ specificity of lymphocyte migration is determined by selective interaction of lymphocytes with specialized endothelial cells. Mouse Peyer's patch and lymph node lymphocytes bind preferentially to high endothelial venules (HEV) in frozen sections of Peyer's patches and peripheral nodes, respectively, and this in vitro binding preference accurately predicts their differential segregation in vivo 30 min after i.v. injection. Both in vivo and in vitro, about 1.4 times as many as many Peyer's patch as lymph node lymphocytes bind HEV in Peyer's patches, and, conversely, twice as many lymph node cells interact with HEV in nonmesenteric lymph nodes. Even greater specificity is shown by certain homogeneous lymphocyte populations, i.e. thymic lymphomas. Some lymphomas bind with remarkable selectivity to HEV in Peyer's patches, and others interact almost exclusively with those in lymph nodes indicating that the mechanisms mediating selective recognition of HEV are capable of nearly absolute discrimination. Mesenteric node HEV are unique in that they allow both Peyer's patch- and lymph node-specific cells to bind. It is proposed that lymphocyte surface receptors specific for organ-restricted endothelial cell determinants mediate the antigen-independent organ specificity of lymphocyte migration. According to this model, there are at least 2 sets of complementary lymphocyte and endothelial cell receptors, one mediating lymphocyte-HEV adherence in Peyer's patches, the other in lymph nodes.

T cell maturation: thymocyte and thymus migrant subpopulations defined with monoclonal antibodies to MHC region antigens

The maturation sequences of thymocytes is known to some extent: A generative layer of subcapsular large lymphoblasts gives rise to a major population of small cortical thymocytes and a minor population of midsize medullary thymocytes. The relative contribution of these three populations to the peripheral T cell populations is not yet known. In this study, subcapsular lymphoblasts, cortical small cells, medullary cells, and thymic emigrant cells have all been analyzed by immunofluorescence for expression of the antigens H-2D, I-A, H-2K, and TL. H-2D is expressed brightly on all subcapsular large cells, dimly on cortical small cells, and brightly on all migrants, cortisone-resistant thymocytes (CRT), and peripheral T cells. I-A can be detected at low levels on 30 to 50% of cells in all the thymic subpopulations, and on 30 to 50% of migrants and peripheral T cells. Fifty to 80% of small cortical cells do not express detectable H-2K, but all the other subpopulations, both inside and outside the thymus, stain uniformly quite brightly. TL3 is expressed on 70 to 80% of subcapsular and cortical thymocytes, 30 to 40% of CRT, is undetectable on migrants but can be seen at low levels on 10 to 20% of spleen and lymph node T cells. The possibility that some or all of these antigens represent stable markers of separate lineages rather than unstable, stage-specific markers is discussed.

T cell maturation: thymocyte and thymus migrant subpopulations defined with monoclonal antibodies to the antigens Lyt-1, Lyt-2, and ThB1

The phenotypes of thymus cells for the antigens Lyt-1, Lyt-2 and ThB have been analyzed by using immunofluorescence techniques. Cells throughout the intrathymic maturation sequence have been tested, including the primitive subcapsular lymphoblasts, all size classes of cortical and medullary thymocytes, and thymus cell emigrants. ThB antigen is not detectable on migrant cells, but all subpopulations in the thymus are subdivided into two categories, bright and dull. Thus, it is possible that the bright and dull phenotypes represent a lineage specific rather than a stage-specific marker, at least inside the thymus. The Lyt-defined thymocyte subclasses Lyt1+2+-(Lyt-1) and Lyt 1+2+ (lyt-1,2) are also both represented in all subpopulations, including subcapsular lymphoblasts. This suggests that they may represent two separate lineages, and that the Lyt-12(3) class is not a precursor of the Lyt-1 class, although the possibility of a very early Lyt-(12(3) cell precursor common to both lines cannot be ruled out.

T cell maturation: thymocyte and thymus migrant subpopulations defined with monoclonal antibodies to the antigens Lyt-1, Lyt-2, and ThB1

The phenotypes of thymus cells for the antigens Lyt-1, Lyt-2 and ThB have been analyzed by using immunofluorescence techniques. Cells throughout the intrathymic maturation sequence have been tested, including the primitive subcapsular lymphoblasts, all size classes of cortical and medullary thymocytes, and thymus cell emigrants. ThB antigen is not detectable on migrant cells, but all subpopulations in the thymus are subdivided into two categories, bright and dull. Thus, it is possible that the bright and dull phenotypes represent a lineage specific rather than a stage-specific marker, at least inside the thymus. The Lyt-defined thymocyte subclasses Lyt1+2+-(Lyt-1) and Lyt 1+2+ (lyt-1,2) are also both represented in all subpopulations, including subcapsular lymphoblasts. This suggests that they may represent two separate lineages, and that the Lyt-12(3) class is not a precursor of the Lyt-1 class, although the possibility of a very early Lyt-(12(3) cell precursor common to both lines cannot be ruled out.

T cell maturation: thymocyte and thymus migrant subpopulations defined with monoclonal antibodies to MHC region antigens

The maturation sequences of thymocytes is known to some extent: A generative layer of subcapsular large lymphoblasts gives rise to a major population of small cortical thymocytes and a minor population of midsize medullary thymocytes. The relative contribution of these three populations to the peripheral T cell populations is not yet known. In this study, subcapsular lymphoblasts, cortical small cells, medullary cells, and thymic emigrant cells have all been analyzed by immunofluorescence for expression of the antigens H-2D, I-A, H-2K, and TL. H-2D is expressed brightly on all subcapsular large cells, dimly on cortical small cells, and brightly on all migrants, cortisone-resistant thymocytes (CRT), and peripheral T cells. I-A can be detected at low levels on 30 to 50% of cells in all the thymic subpopulations, and on 30 to 50% of migrants and peripheral T cells. Fifty to 80% of small cortical cells do not express detectable H-2K, but all the other subpopulations, both inside and outside the thymus, stain uniformly quite brightly. TL3 is expressed on 70 to 80% of subcapsular and cortical thymocytes, 30 to 40% of CRT, is undetectable on migrants but can be seen at low levels on 10 to 20% of spleen and lymph node T cells. The possibility that some or all of these antigens represent stable markers of separate lineages rather than unstable, stage-specific markers is discussed.

Murine leukaemogenesis: monoclonal antibodies to T-cell determinants arrest T-lymphoma cell proliferation

We have proposed a receptor-mediated leukaemogenesis hypothesis wherein T lymphomas would be clones of T cells bearing mitogen-linked surface receptors specific for the envelope determinants of the inducing MuLV. A prediction of the hypothesis is that T-lymphoma proliferation is dependent on continued presentation of MuLV envelope determinants to these cell-surface receptors, and that substances which interfere with receptor-virus interactions should inhibit T-lymphoma proliferation. Rat monoclonal antibodies were raised to the AKR mouse T lymphoma KKT-2, and these antibodies were screened independently for blockade of virus-binding and for cytostatic activity on KKT-2 cells. We report here that those monoclonal antibodies which block virus binding inhibit growth of KKT-2 cells in vitro, whereas monoclonal antibodies which bind to these cells but do not block virus binding are not cytostatic. Three of the four cytostatic antibodies detect determinants on the Thy-1 molecule, while none of the other (noncytostatic) antibodies detect Thy-1. Antibody inhibition of KKT-2 cell growth is precluded by saturation of KKT-2 virus receptors with the inducing leukaemia virus.

Immunoelectron microscopy of cell surface antigens: a quantitative analysis of antibody binding after different fixation protocols

The effect of different fixation solutions on the denaturation of membrane-associated antigens in murine lymphoid cells was determined quantitatively using microfluorometric analysis and a radioimmunoassay. Paraformaldehyde and periodate-lysine-paraformaldehyde solutions preserved the antigenicity of cell surface-associated immunoglobulin (S-Ig) antigens when used in concentrations ranging from 0.01 to 4%. However, glutaraldehyde destroyed the antigenicity of S-Ig and Thy 1.2 molecules at concentrations higher than 0.1%. Electron microscopic analysis of the different fixed cell suspensions, after labelling of the cells with a rabbit anti-mouse immunoglobulin-horseradish peroxidase conjugate (RaM-Ig-HRP) showed that prefixation of the sample with 0.1% glutaraldehyde was optimal for immunoelectron microscopical studies, since this concentration preserved both the antigenicity of membrane-associated antigens as well as the ultrastructure of the cells under study. Prolonged fixation periods affected antibody binding. However, S-Ig molecules denatured at a slower rate than Thy 1.2 molecules. A preparation method for the immunoelectron microscopical localization of lymphoid and non-lymphoid cell types in lymphoid organs is reported.

V-J joining of immunoglobulin kappa genes only occurs on one homologous chromosome

In general, heterozygous animal cells express both alleles at a particular locus. The only exceptions are cells of XX genotype after inactivation of one X chromosome, and immunoglobulin-producing cells; in each case only one of the two alleles is expressed in differentiated cells and their progeny. This phenomenon, termed allelic exclusion, has been described for several mammalian species including man and mouse. It has been shown that the variable (V) and constant (C) region genes of immunoglobulins undergo a rearrangement during ontogeny. We wished to test whether allelic exclusion in B cells could be the consequence of V- and C-region rearrangement on one of the two homologous chromosomes only. For that reason we chose to analyse the rearrangement of immunoglobulin light chain genes in normal B lymphocytes isolated on the fluorescence-activated cell sorter. We now present evidence that during normal B-lymphocyte differentiation V-C rearrangement occurs only on one chromosome.

Thymus cell migration. Quantitative aspects of cellular traffic from the thymus to the periphery in mice

We have used intrathymic injection of fluorescein isothiocyanate to label thymocytes in situ. The method gives random labeling of the thymocyte population and so can be used to quantitate the extent of migration of cells from the thymus to the periphery. Migrant cells can be visualized in frozen sections or cell suspensions of peripheral organs by their fluorescence. Our data show that in young adults, about 1% of thymocytes leave the thymus per day. Since the bulk of thymocytes turn over every 5 to 7 days, this indicates that the vast majority (95%) of thymocytes die within the thymus. Cells that do leave the thymus, go mainly to the T areas of lymph nodes, spleen and Peyer's patches. Migrants are extremely rare in bone marrow, gut and liver. Migration is about the same in neonates as in adults relative to the size of the thymus, but is considerably lower in older animals where it is only about 0.1% of thymocytes per day at the age of six months.

An immunoglobulin heavy-chain gene is formed by at least two recombinational events

The events of B-cell differentiation can be reconstructed in part through an analysis of the organisation of heavy-chain gene segments in differentiated B cells. A mouse immunoglobulin alpha heavy-chain gene is composed of at least three noncontiguous germ-line DNA segments--a VH gene segment, a JH gene segment associated with the Cmu gene segment, and the C alpha gene segment. These gene segments are joined together by two distinct types of DNA rearrangements--a V-J joining and a CH switch.

Organization of kappa light chain genes in germ-line and somatic tissue

We studied the organization of the kappa light chain genes in germ-line (sperm) and somatic (embryo) tissues. We constructed a plasmid containing a DNA insert coding for the kappa chain MOPC 167 and used the Southern blotting technique to determine the organization of kappa variable and constant region genes. In the haploid genome of the mouse there is only one constant region gene detectable and it has the same organization in sperm and embryo DNAs. There are several variable region genes in sperm and embryo that are related to the Vk167 gene. The organization of the V genes in sperm and embryo DNAs is identical. These results show that there is no rearrangement of variable region genes (or "minigenes") during early embryogenesis.

The pathology and homing of a transplantable murine B cell leukemia (BCL1)

The pathology and homing characteristics of a murine B cell leukemia are described. Experiments utilizing autoradiography to determine the early homing pattern of the leukemic cells revealed a pronounced localization of the labeled cells to the spleen. The cells that were seen in the white pulp showed preferential localization to the follicles or B cell domains. Tissue section immunofluorescence with antibodies to kappa- and lambda-light chains was used to study the initial mouse with this disease as well as to study the mice that were injected with in vivo passaged cells. These mice also showed predominant involvement of the spleen. Although the initial mouse with this disease had 200,000 lambda-bearing B lymphocytes per mm3 in the peripheral blood and closely resembled a human chronic lymphocytic leukemia patient, the studies described suggest that this murine B cell neoplasm is a lymphoma with a striking predilection for splenic involvement. The other organs including the bone marrow as well as the peripheral blood appeared to be involved secondarily. This unusual spontaneously occurring murine B cell disease provides a useful model for the investigation of certain commonly occurring human lymphomas and leukemias.

Allogeneic cytolysis of reconstituted membrane vesicles

The successful use of lipid bilayer model membranes as targets for cytotoxic lymphocytes is described. Lipid vesicles were made from a mixture of dipalmitoyl lecithin, dimyristoyl lecithin, and cholesterol. Membrane proteins of LSTRA or EL4 tumor cells (as source of H-2 antigens), human eye muscle membrane proteins (as supporting proteins), and 51Cr marker were inserted into the lipid vesicles. Incubation of the reconstituted vesicles with lymphocytes sensitized in mixed lymphocyte cultures against allogeneic cells resulted in the specific release of intravesicular 51Cr. Vesicle damage was mediated by thymus-derived lymphocytes. H-2 antigens could be incorporated into vesicles without eye muscle proteins. However, immune damage of the vesicles could not be demonstrated when vesicles inserted with H-2 antigens in the absence of eye muscle proteins were used as targets.

A serologic comparison of Moloney lymphoma cell surface and Moloney oncornavirus antigens

Moloney lymphomas and Moloney sarcomas share strong tumor antigens. In this report we analyze the cell-surface antigens on a Balb/c Moloney lymphoma, LSTRA, using hyperimmune sarcoma regressor sera (alphaMo) as a primary reagent. We also use heterologous anti-viral p30 and gp70 sera for a direct analysis of virion protein antigens on the LSTRA surface. Using radiolabeled alphaMo-binding assays, we demonstrate that LSTRA tumor antigens detected by these sera are all Moloney viral antigens; approximately 1/3 of these antigenic determinants are expressed on the intact virus, and the other determinants are revealed by detergent lysis of the virus. The major viral antigens expressed on the LSTRA cell surface are viral env gene products, whereas gag gene products are only sparsely represented. We conclude that alphaMo sera detect almost exclusively viral antigens on LSTRA cells, and these antigens are almost exclusively virion env gene products.

Expression of MHC antigens by mouse thymic dendritic cells

Thymic epithelial cells express MHC antigens in several different patterns. I-A is present throughout the thymic cortex on dendritic cells. The remainder of the I region and H-2K/D are expressed on dendritic cells apparently only variably in the cortex (at least in some haplotypes). All MHC antigens tested are present in the medulla on epithelial cells; expression on medullary lymphocytes cannot be evaluated. Monoclonal anti-MHC antibodies confirm these results. The significance of these findings to T cell maturation is discussed.

AKR leukemogenesis: identification and biological significance of thymic lymphoma receptors for AKR retroviruses

We have previously demonstrated that in vitro cell lines of mouse thymic lymphomas express surface receptors specific for the retrovirus that induced them. This study extends these observations to an analysis of receptor-bearing cells in the preleukemic and leukemic phases of spontaneous AKR thymic lymphomagenesis. AKR mice regularly begin expressing N-tropic retroviruses (as assayed on NIH fibroblasts by the XC plaque assay) in several tissues early in life; thymic lymphocytes also express these viruses, but are not autonomously transformed. Later thymic lymphomas emerge which are capable of metastasizing in the host of origin or transplanting leukemias into syngeneic hosts. Just prior to the appearance of thymic lymphomas, these mice also begin producing xenotropic retroviruses [as assayed in xenogeneic (For example, mink) fibroblasts], and concomitant with the appearance of the leukemias is the appearance of "recombinant" retroviruses which cause mink fibroblast foci (MCF); these viruses express elements of both N- and X-tropic virus envelopes and N-tropic viral gene products in their cores. Spontaneous AKR leukemias also produce other retroviruses which do not cause XC plaques or mink fibroblast foci; these are called SL viruses. The subject of this study was to test whether in vivo thymocytes in the preleukemic and leukemic periods also bear receptors specific for N-tropic, recombinant MCF and SL AKR retroviruses. We demonstrated that each spontaneous thymic lymphoma does bear receptors that bind viruses produced by the lymphomas and MCF-247 to a high degree and that bind N-ecotropic AKR retroviruses less well. Thymic lymphocytes predominating in the preleukemic period do not express detectable levels of receptors for either of the viruses. In some mice, receptor-positive cells co-exist with receptor-negative cells; only the receptor-positive cells are capable of transplanting leukemia to syngeneic hosts. We conclude that the presence of specific cell surface receptors for lymphoma cell-produced and recombinant AKR retroviruses is a marker for leukemia in these hosts.

Specificity of cell surface virus receptors on radiation leukemia virus and radiation-induced thymic lymphomas

We have developed a system for analysis of murine leukemic virus (MuLV) receptors on the surface of thymic lymphoma cells utilizing the fluorescence-activated cell sorter. The binding of fluoresceinated or rhodaminated MuLV to target cells showed saturation kinetics and was blocked by homologous MuLV, and bound MuLV had a polypeptide profile identical to that of input MuLV. Thymic lymphomas bound specifically the MuLV which induced them, whereas only 0.5 to 2% of normal thymocytes showed equivalent MuLV binding. Simultaneous binding of excess fluoresceinated RadLV and rhodaminated MCF-247 AKR virus to radiation leukemia virus-induced or spontaneous AKR thymic lymphomas demonstrated that even in the presence of both viruses the cells bound preferentially the inducing MuLV. Examination of the C57BL/Ka endogenous viruses showed that radiation leukemia virus-induced thymic lymphomas bind only thymotropic-leukemogenic radiation leukemia virus and not eco- or xenofibrotropic MuLV's. Thus, virus binding in this system involves only leukemogenic isolates of these retroviruses and implies a central role of this receptor-ligand interaction in the processes of leukemic transformation.

Retrovirus purification: method that conserves envelope glycoprotein and maximizes infectivity

A Sepharose 4B chromatographic method for purification of retroviruses is described which was less time consuming, increased purified virus yields, conserved viral glycoprotein, and increased recovery of biological infectivity in comparison with conventional sucrose gradient ultracentrifugation techniques.

The lymphoid system. Its normal architecture and the potential for understanding the system through the study of lymphoproliferative diseases

This article presents a view of lymphoid tissue architecture as defined by the traffic of defined lymphoid cell classes. The compartmentalization of lymphocytes is discussed in reference to specific cell-cell interactions that occur in antigen-driven immune responses. Finally, the distribution of normal and neoplastic lymphocytes in humans is defined and compared with animal model systems.

Evidence that MuLV-induced thymic lymphoma cells possess specific cell membrane binding sites for MuLV

Cell-surface binding sites specific for thymotropic murine leukemia viruses were found in high concentrations on thymic lymphoma cell lines induced by this class of virus, but were detectable in much lower concentrations (if at all) in several non-T leukemias, plasmacytomas, and normal thymocytes or spleen cells. By specific comparison, Moloney leukemia virus (M-MuLV) binds to a lymphoma induced by M-MuLV, but not to a thymic lymphoma induced by Gross leukemia virus (G-MuLV); and G-MuLV binds to an AKR lymphoma but not to the M-MuLV-induced lymphoma. The material which binds to these T-lymphoma membrane sites is input virus, rather than a contaminant which copurifies with virus. Autoradiographic analysis demonstrates that a high proportion of T-lymphoma cells possess binding sites, whereas only a rare cell in the thymus binds murine leukemia virus to the same degree. We raise and discuss the hypothesis that each T lymphoma induced by thymotropic leukemia viruses may represent the clonal descendants of the few rate cells in the normal thymocyte population which also bind these viruses.

Focal infection and transformation in situ of thymus cell subclasses by a thymotropic murine leukemia virus

Studies on the maturational lineages of thymic lymphocytes have revealed several subclasses which are distinguishable on the basis of cell size, topographic distribution within the thymus, DNA synthetic and mitotic activity, migratory behavior, and other properties. Strain C57BL/Ka mice were inoculated with radiation leukemia virus at different concentrations, and tissues were removed at defined intervals. Sequential sections were analyzed for virus-specific cytoplasmic antigen expression, for morphological evidence of neoplastic transformation, and for alkaline phosphatase activity. The first detectable sign of MuLV infection was the focal appearance of cytoplasmic viral antigens in cells of the outer thymic cortex, followed by coalescence of such foci and, several weeks later, by the appearance of morphologically transformed and alkaline phosphatase-positive cells, again often focally distributed in the outer thymic cortex. These observations strongly suggest that the large, mitotically active cells of the outer thymic cortex are the principal source of target cells for both productive infection and subsequent lymphoma induction by the virus.

Evidence that uridine incorporation is not a selective marker for mouse lymphocyte subclasses

We demonstrate here that mouse T+ and Ig+ lymphocytes do not show the differential incorporation of 3H-uridine into acid precipitable cellular components described for these lymphocyte subpopulation in the rat.

In vitro cortisone sensitivity of in vivo cortisone-resistant thymocytes

Thymus cells from untreated or hydrocortisone-treated mice were cultured for 20 hr in the presence or absence of a water-soluble glucocorticoid, hydrocortisone sodium succinate. By two independent assays of cell viability or function, virtually all thymocytes from untreated hosts were inactivated by hydrocortisone sodium succinate, whereas most, but not all, thymocytes from hydrocortisone-treated hosts were inactivated. Thus, the thymocytes which survive after treatment of the animal with glucocorticoids are only partially resistant to the effects of glucocorticoids in vitro.

EEG in ulcerative colitis

Electroencephalographic tracings of 50 patients with ulcerative colitis (UC) were compared with those of 75 controls. In the UC patients a 24% incidence of abnormal tracings was found as compared with an 8% incidence in the controls. A higher incidence of abnormal electroencephalograms was found among active cases of UC than among those in remission. The meaning of these results is not yet clear.