Analysis of candidate human blood stem cells in "humanized" immune-deficiency SCID mice

Immune deficient SCID mice support the hematopoietic development of surgically implanted human fetal thymus and bone. The usability of the resulting SCID-hu hematolymphoid chimaera as an assay system for human candidate blood stem cells was suggested by the observation that allogeneic CD34+ cells sorted from fetal liver and bone marrow can engraft and differentiate in the transplanted human thymus and bone marrow. The SCID-hu mouse has been further used, in combination with a mouse bone marrow stromal cell line that supports human myeloid and B lymphoid differentiation in vitro, to identify a minor subset of fetal CD34-expressing cells that exhibit multilineage hematopoietic potentialities.

Cloning and characterization of cyclophilin C-associated protein: a candidate natural cellular ligand for cyclophilin C

We report the protein purification and the cloning and characterization of a cDNA encoding the proteins that bind with high affinity to cyclophilin C (Cyp-C) in the absence of cyclosporin A. Transfection of this cDNA into COS cells directs the production of a glycoprotein of 77 kDa that binds to Cyp-C in the absence, but not the presence, of cyclosporin A. Homology comparisons reveal that this protein and gene, termed CyCAP for Cyp-C-associated protein, possess a cysteine-rich domain (scavenger receptor cysteine-rich domain) found in a variety of cell-surface molecules; the rest of the sequence is apparently specific. This result raises the possibility that Cyp-C serves as a mediator or regulator of an as-yet-unidentified signal or cellular process initiated via the Cyp-C-associated protein.

Characterization of posttransplant lymphomas that express T-cell-associated markers: immunophenotypes, molecular genetics, cytogenetics, and heterotransplantation in severe combined immunodeficient mice

Immunosuppressed individuals are at high risk for the development of hematologic malignancies. The typical lymphomas arising in organ transplant recipients are B-cell non-Hodgkin's lymphomas that contain Epstein-Barr virus (EBV) DNA sequences. We investigated the characteristics of posttransplant lymphomas that lacked expression of the usual markers associated with EBV transformation. We describe four large-cell lymphomas seen recently at our institution. Two of these four cases were CD4+, one was CD8+, and in one staining for CD4 and CD8 expression was not performed. One CD4+ lymphoma was a CD30+, EBV- large-cell lymphoma from a 65-year-old kidney transplant recipient, the second was an EBV+ large-cell lymphoma from a 25-year-old heart transplant patient. Two T-cell lymphomas were EBV+ and had clonal T-cell receptor beta gene rearrangements. The other two lymphomas expressed T-cell markers CD4 and CD43, and lacked expression of B-cell markers CD19, CD20, CD21, CD22, CD23, and surface Ig. Both CD4+ lymphomas were tumorigenic after their heterotransplantation into severe combined immunodeficient (SCID) mice. Cytogenetics, immunophenotyping, and genotyping of the secondary tumors from SCID mice showed their clonality and identity with the patients' primary tumors. Novel CD4+ lymphoma cell lines, LH521/4 and LK418/4, were established from tumors that had been passaged in SCID mice. An immunodeficient environment may facilitate the growth of these T-cell or biphenotypic lymphomas; the etiology of their genesis can include transformation with EBV and other, as yet unidentified mechanisms.

Cystic kidney dysplasia and polydactyly in 3 sibs with Bardet-Biedl syndrome

Two infants with cystic kidney dysplasia and polydactyly were born to consanguineous parents. One infant died at age 2 months, and the other is currently 3.5 years old. A third pregnancy was terminated following ultrasonographic visualization of large echo-dense fetal kidneys and polydactyly. Although none had apparent brain anomalies, they were considered to represent the Meckel syndrome. Extinguished responses on electroretinography in our 3.5-year-old patient has led to the diagnosis of Bardet-Biedl syndrome. This observation offers an opportunity to revisit the Bardet-Biedl syndrome and provides further evidence that structural renal abnormalities are characteristic of the syndrome. We wish to alert the clinician to the diagnosis of Bardet-Biedl syndrome in patients with infantile cystic kidney dysplasia.

The in vitro response of phenotypically defined mouse stem cells and myeloerythroid progenitors to single or multiple growth factors

Pluripotential stem cells (Thylo Lin- Sca+; referred to as Sca+) and primitive myeloerythroid progenitor cells (Thylo Lin- Sca-; referred to as Sca-), defined by their in vivo repopulating properties, have been purified from mouse bone marrow. In this study, the growth factor requirements of these two subsets were compared in colony-forming assays. Sca- progenitor cells grew well in interleukin (IL) 3 alone and showed maximum growth when two factors, IL-3 plus IL-1 or IL-3 plus IL-6, were combined. In contrast, Sca+ stem cells were generally not responsive to any single factor tested. Some colony formation was found when IL-3 was paired with either IL-1 or IL-6, and this was significantly enhanced as additional factors were included. A remarkable frequency of as much as 1 colony per 1.7 input Sca+ cells was achieved when IL-1, IL-3, IL-6, and colony-stimulating factors were used together. These differences in factor requirements presumably reflect the need for multiple factor signaling in the more primitive stem cell population. In most other aspects of colony formation, Sca+ and Sca- cells were very similar. They generated colonies that had equivalent distributions in size and cellular composition. One notable difference was found in the kinetics of their response. Whereas nearly all Sca- cells formed colonies within 7 days, a significant fraction of Sca+ cells delayed colony formation for greater than 1 week. During this quiescent period, cell survival was absolutely dependent on the presence of factors in the medium.

Two cytoplasmic candidates for immunophilin action are revealed by affinity for a new cyclophilin: one in the presence and one in the absence of CsA

We report the cloning and characterization of a new binding protein for the immunosuppressive drug cyclosporin A (CsA). This new cyclophilin, cyclophilin C (cyp C), shows extensive homology with all previously identified cyclophilins. Cyp C mRNA is expressed in a restricted subset of tissues relative to cyclophilins A and B, but is present in those tissues reported to be most affected by CsA therapy. A cyp C fusion protein has peptidyl-prolyl isomerase activity, and CsA inhibits this activity. Using the cyp C fusion protein as an affinity ligand to probe cellular extracts, we find that the cyp C fusion protein binds specifically to a 77 kd protein in the absence of CsA, while in the presence of CsA it instead binds specifically to a 55 kd protein. We propose that the p77 is involved in cyp C native function and that the p55 is involved in signal transduction events blocked by treatment with immunosuppressive levels of CsA.

Calcineurin is a common target of cyclophilin-cyclosporin A and FKBP-FK506 complexes

Although the immediate receptors (immunophilins) of the immunosuppressants cyclosporin A (CsA) and FK506 are distinct, their similar mechanisms of inhibition of cell signaling suggest that their associated immunophilin complexes interact with a common target. We report here that the complexes cyclophilin-CsA and FKBP-FK506 (but not cyclophilin, FKBP, FKBP-rapamycin, or FKBP-506BD) competitively bind to and inhibit the Ca(2+)- and calmodulin-dependent phosphatase calcineurin, although the binding and inhibition of calcineurin do not require calmodulin. These results suggest that calcineurin is involved in a common step associated with T cell receptor and IgE receptor signaling pathways and that cyclophilin and FKBP mediate the actions of CsA and FK506, respectively, by forming drug-dependent complexes with and altering the activity of calcineurin-calmodulin.

Culture of phenotypically defined hematopoietic stem cells and other progenitors at limiting dilution on Dexter monolayers

Highly enriched, phenotypically defined hematopoietic stem, Thy-1loLin-Sca-1+, and progenitor cell populations from mouse bone marrow (BM) were tested at limiting dilution for their ability to reconstitute Dexter monolayers. Several classes of BM cells can reconstitute Dexter cultures, first forming discrete "cobblestone" areas which then mature into colonies consisting primarily of maturing myeloid and erythroid cells. Most such colonies have a limited lifespan in culture. Only the Thy-1loLin-Sca-1+ cell fraction gives rise to colonies that survive longer than 3 weeks, which suggests that a limiting-dilution analysis for long-term reconstitution of Dexter cultures can serve as a quantitative measure of stem cell activity. Additional experiments were performed to assess the formation of new progenitor cells in reconstituted Dexter cultures. Again, only cultures seeded with the stem cell-enriched fraction contained expanded numbers of replatable WEHI-3 CM responsive colony-forming cells (CFU-GM). Quantitative analysis indicates that 97% of the replatable CFU-GM of whole BM is contributed by the Thy-1loLin-Sca-1+ cell fraction, again suggesting a potential stem cell-specific assay. Such quantitative in vitro assays might prove useful in characterization and isolation of human stem cells where in vivo assays are lacking.

Most CD8+ cells in skin lesions of CD3+ CD4+ mycosis fungoides are CD3+ T cells that lack CD11b, CD16, CD56, CD57, and human Hanukah factor mRNA

To define further the characteristics of CD8+ cells in skin lesions of CD3+ CD4+ mycosis fungoides (MF), the authors used single- and double-label immunohistologic techniques and in situ hybridization to detect antigens and transcripts associated with certain types of cytotoxic or suppressor function. The cytotoxic markers included CD16, CD56, CD57, and an anti-sense probe for human Hanukah factor (HuHf) mRNA. Analysis of 23 cases demonstrated that lesional CD8+ cells were CD3+ T cells that generally lacked expression of any of the cytotoxic markers studied. Analysis of another 10 cases confirmed the CD3+ T-cell lineage of lesional CD8+ cells and demonstrated that these cells also lacked expression of the suppressor-associated marker, CD11b. In aggregate, these results indicate that most CD8+ cells in CD3+ CD4+ MF skin lesions are of T-cell rather than NK-cell differentiation. Their overall phenotype suggests that they may be major histocompatibility complex (MHC)-restricted cytotoxic T cells lacking appreciable levels of HuHF serine protease. Because the induction of CD8+ suppressor T cells is mediated by CD4+ T cells expressing the CD45RA+ RO- phenotype, CD45 epitope expression was studied in 15 MF cases. The vast majority (13/15) contained CD3+ CD4+ tumor cells that were CD45+ RA- RB+ RO+ 2B11+. This phenotype is consistent with memory T cells rather than suppressor-inducer T cells, and correlates with the paucity of phenotypically defined suppressor T cells in CD3+ CD4+ MF skin lesions.

Granzyme A and perforin as markers for rejection in cardiac transplantation

The use of granzyme A and perforin as markers for rejection after cardiac transplantation has been investigated. Using in situ hybridization we have detected lymphocytes expressing granzyme A and perforin RNA that are infiltrating the donor heart after transplantation. A total of 29 different biopsies from 17 different patients who had undergone cardiac transplantation were examined. Twelve biopsies classified by conventional histological criteria as showing evidence of rejection were found to contain lymphocytes expressing granzyme A and perforin. Seven biopsies classified as showing no histological evidence of rejection infiltrating lymphocytes were found not to be expressing granzyme A or perforin. However, in 10 other biopsies from 5 different patients that had been classified as showing no evidence of rejection by the conventional grading system, lymphocytes expressing granzyme A and perforin were detected. In six of these cases the patient was found to have undergone a subsequent rejection episode. In the other four cases the biopsies were either taken at a very early stage after transplantation and the high doses of immunosuppression used routinely at that stage are likely to have averted any rejection episodes, or it was not possible to follow subsequent rejection episodes. These results, which are statistically significant (p = 0.06), demonstrate that granzyme A- and perforin-expressing lymphocytes can be identified in rejecting biopsies before histological damage is seen. The identification of perforin and granzyme A expression in vivo suggest a possible role for these proteins in the cytolysis that occurs during transplantation rejection. Furthermore, the data presented here suggest that it may be possible to use granzyme A and perforin as early predictive markers of transplantation rejection.

IgH enhancer deregulated expression of L-myc: abnormal T lymphocyte development and T cell lymphomagenesis

Transgenic constructs containing the murine L-myc gene under the control of the immunoglobulin transcriptional enhancer element (Emu) are expressed at unexpectedly high levels in thymocytes and proliferating T cells compared with cells from bone marrow and proliferating B cells. In contrast, double transgenic animals bearing constructs containing the L- and N-myc genes similarly linked to the Emu element maintain preferential L-myc expression in T cells but express the N-myc transgene preferentially in B cells. These results indicate that the L-myc gene contains elements that act in concert with the Emu element to allow preferential expression in T lineage cells. In correspondence to the expression pattern, Emu-L-myc transgenic mice show expanded thymic cortices and irregularly formed splenic follicles with expanded T cell areas. Moreover, the percentage of thymocytes positive for the surface marker 1C11, which defines thymic progenitor cells, activated T cells and preleukemic T cells, is dramatically raised in transgenic mice compared with normal littermates. Emu-L-myc transgenic animals are predisposed to clonal lymphoid tumors, most of which are T cell lymphomas. The relative incidence, latency period, and degree of malignancy of Emu-L-myc tumors compared with Emu-N- or c-myc tumors is consistent with a lower oncogenic potential of the L-myc gene. However, the Emu-L-myc tumors do not express detectable levels of endogenous myc family genes indicating that the L-myc protein can substitute for c- or N-myc in the generation and growth of lymphoid neoplasms.

A new method for stoichiometric analysis of proteins in complex mixture--reevaluation of the stoichiometry of E. coli ribosomal proteins

A novel way is presented for determination of the stoichiometry of ribosomal proteins in the ribosome. The 70S E. coli r-proteins, completely separated on a two-dimensional gel system, were used throughout our experiments. The method is based on our previous observation that the amount of Coomassie R bound to a protein molecule is directly proportional to the number of positive charges on that protein. By plotting the amount of bound Coomassie as a function of the number of positive charges of each r-protein, and relating the experimental amount of the dye bound to each r-protein to the value obtained from the linear regression line based on all (a total of some 50 proteins), one can obtain the molar concentration of every protein in the ribosome. A parallel experiment can be carried out, which relates the radioactivity contributed by 3H-labeled amino acid in each r-protein to its amino acid content in that molecule. The two sets of data, which are completely independent of each other, are well correlated. Further verification of the validity of our procedure is provided by the fact that we found the known proportions of four copies of L7/L12 and one copy of S6 per ribosome. The rationale behind the present study was our finding that recalculation of Hardy's data (Hardy, S.J.S. (1975) Mol. Gen. Genet. 140, 253-274), with the accurate molecular weight value of the r-proteins provided by Giri et al. (Adv. Protein Chem. (1984) 36, 1-78), raises some doubt with regard to his experimental results, although we agree with his final conclusion that E. coli ribosome is homogeneous with respect to its proteins.

Concentric and eccentric torque variations of the quadriceps femoris in patellofemoral pain syndrome

The purpose of this study was to investigate the extent of torque reduction in the quadriceps femoris in subjects complaining of patellofemoral pain syndrome compared to subjects with sound knees. Fifty-five patients (21 women and 34 men) and 30 healthy subjects (15 women and 15 men) took part in this study. Using the KINCOM isokinetic dynamometer, quadriceps torque was assessed at 30°/s, 60°/s, and 120°/s, both in the concentric and eccentric modes. Findings demonstrated a significant (P < 0·01) reduction of between 30% and 40% in the patients when compared with the control group. This reduction was not speed or mode-specific. Men were stronger than women by a margin of 22% and 14% for the concentric and eccentric modes in the control group. Parallel figures for the patellofemoral pain syndrome group were 25% and 17%. Good to high correlations were found between peak and average torque in both groups. There were no significant differences between the muscles referring to the dominant versus the non-dominant legs of the control group.

B cell infiltration of the thymic medulla in New Zealand black, New Zealand white, and (New Zealand black x New Zealand white)F1 mice. Effect of total lymphoid irradiation

Thymuses from female (New Zealand black x New Zealand white)F1 [( NZB x NZW]F1), New Zealand black, and New Zealand white mice of different ages were examined by immunohistochemical and flow cytometric analysis. Two-and-a-half-month-old (NZB x NZW)F1 mice showed infiltration of the thymus with B cells, and by 6-8 months of age, showed a disruption of the entire medullary area. More than 80% of the thymic B cells had the phenotypic characteristics of conventional B cells (IgM+, IgD+, Ly-1-). Total lymphoid irradiation induced a marked depletion of medullary B cells and a restoration of the thymic architecture.

Role of interleukin-4 in T-cell ontogeny: changes in cell surface phenotype and lymphokine production of immature thymocytes after culture with interleukin-4 and phorbol ester

We have analyzed the phenotype and functional capabilities of adult and fetal CD4 8 thymocytes after 4 d of culture in IL-4 and PMA. Both adult and day 14 fetal CD4 8 thymocytes failed to acquire CD4 or CD8 antigens following culture. However, changes in expression of other antigens typical of immature thymocytes were observed. For example, the frequency with which cells expressed high levels of J11d or IL-2-R was greatly decreased following culture, whereas the frequency with which high levels of MEL-14, the lymph node homing receptor were expressed were greatly increased. This phenomenon may be due to direct induction by IL-4 and PMA of MEL-14 expression on purified MEL-14lo CD4-8- thymocytes. The frequency of cells expressing CD3, Ly-1 and Pgp-1 changed only slightly. Functionally, the cultured cells produced large amounts of interferon gamma but very little IL-2 or IL-4, although freshly isolated CD4-8- thymocytes produced all three lymphokines. These results suggest that in addition to a proliferative stimulus, culture in IL-4/PMA alters the expression of several early thymocyte antigens, the functional capabilities of CD4-8- progenitor thymocytes, and may act as a selective differentiation stimulus to MEL-14lo CD4-8- thymocytes.

Nonocclusive ischaemic bowel disease in patients on chronic haemodialysis

Six patients with chronic renal failure on longstanding haemodialysis are presented, in whom nonocclusive bowel ischaemia occurred as a rare complication of their underlying disorder. Factors implicated in the development of bowel ischaemia in these patients are chronic constipation resulting in increased intraluminal pressure on the bowel wall, premature and progressive arterial disease and bouts of hypotension accompanying the haemodialysis procedure. Contrast studies of the bowel and computed tomography examination can suggest the diagnosis, but angiography alone provides the exact answer in demonstrating nonocclusive mesenteric ischaemia. In patients with chronic renal failure and longstanding dialysis presenting with abdominal symptoms this diagnosis should be considered.

Total lymphoid irradiation leads to transient depletion of the mouse thymic medulla and persistent abnormalities among medullary stromal cells

Mice given multiple doses of sublethal irradiation to both the thymus and the peripheral lymphoid tissues showed major transient, and some persistent disruptions in general thymic architecture and in thymic stromal components. At 2 wk after total lymphoid irradiation (TLI), the thymus lacked identifiable medullary regions by immunohistochemical analyses. Medullary stromal cells expression MHC Ag or a medullary epithelial cell Ag, as well as medullary macrophages, were undetectable. Instead, the processes of cortical epithelial cells were observed throughout the entire thymus. Strikingly, thymocyte subsets with mature phenotypes (CD4+CD8- and CD4-CD8+) were present in the apparent absence of a medulla. This early, gross effect was rapidly reversed such that by 1 to 2 mo after TLI, medullary areas with MHC Ag-positive cells were evident. However, abnormalities in a subset of medullary stromal cells appeared to be more persistent. Medullary epithelial cells, identified by the MD1 mAb, were greatly reduced in number and abnormally organized for at least 4 mo after TLI. In addition, macrophages containing endogenous peroxidase activity, normally abundant in medullary regions, were undetectable at all times examined after TLI. Therefore, this irradiation regimen induced both transient and long term effects in the thymus, primarily in medullary regions. These results suggest that TLI may be used as an experimental tool for studying the impact of selective depletion of medullary stromal cells on the development of specific T cell functions.

Total lymphoid irradiation leads to transient depletion of the mouse thymic medulla and persistent abnormalities among medullary stromal cells

Mice given multiple doses of sublethal irradiation to both the thymus and the peripheral lymphoid tissues showed major transient, and some persistent disruptions in general thymic architecture and in thymic stromal components. At 2 wk after total lymphoid irradiation (TLI), the thymus lacked identifiable medullary regions by immunohistochemical analyses. Medullary stromal cells expression MHC Ag or a medullary epithelial cell Ag, as well as medullary macrophages, were undetectable. Instead, the processes of cortical epithelial cells were observed throughout the entire thymus. Strikingly, thymocyte subsets with mature phenotypes (CD4+CD8- and CD4-CD8+) were present in the apparent absence of a medulla. This early, gross effect was rapidly reversed such that by 1 to 2 mo after TLI, medullary areas with MHC Ag-positive cells were evident. However, abnormalities in a subset of medullary stromal cells appeared to be more persistent. Medullary epithelial cells, identified by the MD1 mAb, were greatly reduced in number and abnormally organized for at least 4 mo after TLI. In addition, macrophages containing endogenous peroxidase activity, normally abundant in medullary regions, were undetectable at all times examined after TLI. Therefore, this irradiation regimen induced both transient and long term effects in the thymus, primarily in medullary regions. These results suggest that TLI may be used as an experimental tool for studying the impact of selective depletion of medullary stromal cells on the development of specific T cell functions.

Approaches to an understanding of pathogenetic mechanisms in AIDS

AIDS, presumably caused by the human retrovirus, human immunodeficiency virus (HIV), is a disease with multiple pathologies, most of which are the consequence of a profound immunodeficiency. The first two sections of this review focus primarily on the normal development and function of the cells of the immune system and the known abnormalities that occur in this system in AIDS patients. Very little is known of the pathogenesis, in humans, of the four major clinical manifestations of AIDS--immunodeficiency, encephalopathy, Kaposi's sarcoma, and lymphoma. Because most pathologic studies derive from autopsy findings in terminal AIDS patients, it has been difficult to track the course of HIV infection from the time of initial contact with the virus through the evolution of the disease. Therefore, the final section of this review focuses on actual and potential animal models of AIDS and how such models might be valuable for studies on the pathogenesis of the disease, the development of relevant vaccines, and the testing of potential therapies.

The phenotype of thymocytes derived from a single clonogenic precursor

Clonogenic repopulation of the thymus of thymus-homing bone marrow cells leads to intrathymic populations representing all four major Lyt-2- and L3T4-defined phenotypes. Although all four phenotypes may be represented in a single clone, quite often a striking bias in the proportion of L3T4 single positive to Lyt-2 single positive cells may exist within a clone, but not in the host thymocytes in general. Because at any one time these clones may be located in specific subregions of the thymus (specifically cortex only, medulla only, or cortex and medulla), we propose the hypothesis that different microenvironments in the thymus might, in fact, be responsible for the predominant maturation of different single positive mature thymic subsets.

The phenotype of thymocytes derived from a single clonogenic precursor

Clonogenic repopulation of the thymus of thymus-homing bone marrow cells leads to intrathymic populations representing all four major Lyt-2- and L3T4-defined phenotypes. Although all four phenotypes may be represented in a single clone, quite often a striking bias in the proportion of L3T4 single positive to Lyt-2 single positive cells may exist within a clone, but not in the host thymocytes in general. Because at any one time these clones may be located in specific subregions of the thymus (specifically cortex only, medulla only, or cortex and medulla), we propose the hypothesis that different microenvironments in the thymus might, in fact, be responsible for the predominant maturation of different single positive mature thymic subsets.

Papular acrodermatitis with cytomegalovirus hepatitis

The syndrome of papular acrodermatitis of childhood with hepatitis (Gianotti-Crosti syndrome) is classically considered to be associated with hepatitis B surface antigen (HBsAg) infection. We report an infant with the syndrome, but with serological evidence of infection by cytomegalovirus.

Immunoglobulin gene rearrangements in normal mouse B cells

We have analyzed the structure of rearranged mu heavy-chain genes obtained from the genomic DNA of normal BALB/c mouse spleen cells expressing surface immunoglobulin M. Examples were found of two types of nonproductive rearrangements, which may be responsible for allelic exclusion in normal B cells. In one of these rearrangements, a germ line D gene segment has joined to the JH4 gene segment but no V/D joining has occurred. We present evidence that D gene segments lie as a cluster between V and J gene segments in the germ line. A comparison of conserved sequences in V and D gene segments suggests that the D gene segments, which are found only in the heavy-chain gene family, may have evolved from V gene segments similar to the Vk family.

Abnormal migration of T lymphocyte clones

Several in vitro T cell clones were markedly deficient in their ability to home to peripheral lymphoid tissue. This was found for an alloreactive noncytolytic clone, a soluble antigen- (KLH)specific line, and cytotoxic clones specific for allogeneic cells and for Abelson virus-induced lymphoma cells. This abnormal circulation pattern was probably caused by the lack of the receptors of the lymphocytes for high endothelial venules (HEV), as implied by the lack of binding of these T cells to HEV in frozen sections of mouse lymph node and Peyer's patches. The loss of surface receptors that are necessary for normal lymphocyte migration may thereby alter the in vivo function of adoptively transferred T cells.

Abnormal migration of T lymphocyte clones

Several in vitro T cell clones were markedly deficient in their ability to home to peripheral lymphoid tissue. This was found for an alloreactive noncytolytic clone, a soluble antigen- (KLH)specific line, and cytotoxic clones specific for allogeneic cells and for Abelson virus-induced lymphoma cells. This abnormal circulation pattern was probably caused by the lack of the receptors of the lymphocytes for high endothelial venules (HEV), as implied by the lack of binding of these T cells to HEV in frozen sections of mouse lymph node and Peyer's patches. The loss of surface receptors that are necessary for normal lymphocyte migration may thereby alter the in vivo function of adoptively transferred T cells.

Expression of IgD may use both DNA rearrangement and RNA splicing mechanisms

From a library of mouse sperm DNA, we have isolated two overlapping clones which contain the C(delta) gene. One of these clones also contains the C(mu) gene. The C(delta) gene is separated from the C(mu) membrane exons by approximately 2 kilobases (kb) of DAN. The C(delta) gene was identified by (a) hybridization to poly(A)(+)RNA prepared from the IgD-producing rat plasma cell tumor IR731, and (b) homology of a translated nucleotide sequence to the amino acid sequence of the human delta chain. The C(delta) gene spans 8 kb of DNA in the germ line. Plasmid subclones of the C(delta) gene were used as probes in Southern and RNA blot experiments. RNA blot analysis of cytoplasmic poly(A)(+)RNA from IR731 and a mu(+)delta(+) B-cell hybridoma revealed 1.6- and 2.7-kb delta mRNA species with different 3' ends, which presumably encode the secreted and membrane-bound forms, respectively, of the delta chain. Southern blot analysis of DNA from two mu(+)delta(+) lymphomas revealed that the C(delta) gene is in the germ-line configuration in each case. Restriction map analysis of C(mu) and C(delta) genomic clones isolated from a library of normal mu(+)delta(+) B-cell DNA also gave no evidence for DNA rearrangement in the region between the C(mu) and C(delta) genes. Taken together, these data suggest that IgD expression in mu(+)delta(+) B cells does not involve a V(H)-to-C(delta) DNA switch rearrangement. We propose that simultaneous expression of C(delta) and C(delta) with a single V(H) gene is mediated by two alternative routes of RNA processing of a primary nuclear transcript which contains the V(H), C(mu), and C(delta) genes. In contrast, analogous experiments with myeloma IR731 DNA revealed that the C(mu) gene has been deleted from the myeloma DNA and that the C(delta) gene has undergone DNA rearrangement, presumably including a switch recombination of the V(H) gene from the C(mu) to the C(delta) gene. These results indicate that two alternative mechanisms may be used in the expression of IgD molecules-RNA splicing in B cells and DNA rearrangement in plasma cells.

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 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.

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.