Production, selection, and maturation of thymocytes with high surface density of TCR

The main steps in intrathymic T cell differentiation have been defined using bromodeoxyuridine as a postmitotic cell tracer. Thymocytes with a high surface expression of the TCR are generated in the first 24 h after DNA synthesis. The phenotype of these TCR(high) cells was studied during 10 days by using pairs of surface markers associated with BrdUrd. During the first 2 days, TCR(high) cells were of the CD4+CD8+HSA(high) phenotype, transiently expressed the early activation marker CD69, and contained a high percentage of cycling cells. This activation step preceded the transition from CD4+CD8+ to CD4+CD8- and then to CD4-CD8+ cells, followed by progressive HSA down regulation and increase in the expression of H-2K, Qa-2, and CD45RB. The phenotypic maturation was completed in 9 days. In Mls-1a mice, negative selection of V beta 6+ cells was observed at the earliest step of TCR(high) cell generation, and positive selection of V beta 8.2+ and V beta 14+ cells took place later and was correlated to the activation step. These data suggest that high TCR expression and cell activation are necessary for positive selection and subsequent T cell maturation.

[Familial thymoma and translocation t (14;20) (q24;p13)]

A familial lympho-epithelial thymoma with constitutional chromosomal translocation t (14;20) (q24;p13) is presented: the thymoma and its particular translocation are present in the mother and the two sons of her offspring. The small number of cases do not allow establishing any relation between thymoma and this particular translocation. Concerning genetic counseling, an annual thoracic radiography is necessary for all the other family members, carriers or not of the translocation.

Normal sequence of phenotypic transitions in one cohort of 5-bromo-2'-deoxyuridine-pulse-labeled thymocytes. Correlation with T cell receptor expression

"In vivo" kinetics of T cell differentiation and TCR expression in the normal murine thymus were re-evaluated using a new technique for simultaneous detection of bromodeoxyuridine and two surface markers. The transition from CD4-8- precursors to CD4+8+ immature cells was directly observed during cell proliferation, and shown to proceed through transitory intermediates expressing no or low amounts of CD4. CD3-TCR expression also started during this transition and resulted in the production of a majority of TCRlo cells but also of a significant number (1 to 2 x 10(6) of TCRhi immature (heat-stable Ag+) thymocytes. After cessation of proliferation, the maturational transition from CD4+8+ to CD4+8- and CD4-8+ (in this order) was restricted to TCRhi cells produced during CD4+8+ cell generation. The acquisition of the single positive phenotype preceded HSA down-regulation, suggesting that maturation of TCRhi thymocytes proceeds in two separate steps. The major TCRloCD4+8+ subset appeared a dead end subset and showed no up-regulation of TCR expression at any time.

Normal sequence of phenotypic transitions in one cohort of 5-bromo-2'-deoxyuridine-pulse-labeled thymocytes. Correlation with T cell receptor expression

"In vivo" kinetics of T cell differentiation and TCR expression in the normal murine thymus were re-evaluated using a new technique for simultaneous detection of bromodeoxyuridine and two surface markers. The transition from CD4-8- precursors to CD4+8+ immature cells was directly observed during cell proliferation, and shown to proceed through transitory intermediates expressing no or low amounts of CD4. CD3-TCR expression also started during this transition and resulted in the production of a majority of TCRlo cells but also of a significant number (1 to 2 x 10(6) of TCRhi immature (heat-stable Ag+) thymocytes. After cessation of proliferation, the maturational transition from CD4+8+ to CD4+8- and CD4-8+ (in this order) was restricted to TCRhi cells produced during CD4+8+ cell generation. The acquisition of the single positive phenotype preceded HSA down-regulation, suggesting that maturation of TCRhi thymocytes proceeds in two separate steps. The major TCRloCD4+8+ subset appeared a dead end subset and showed no up-regulation of TCR expression at any time.

Phenotype analysis of cycling and postcycling thymocytes: evaluation of detection methods for BrdUrd and surface proteins

We present a comparison of two different methods for simultaneous detection of bromodeoxyuridine and cell surface markers. Both methods use enzymatic generation of single-strand DNA with nuclease. The biological system used is the murine thymus, in which in vivo DNA synthetizing cells were labeled by injection of BrdUrd and analyzed at different time points after the nucleoside pulse. The surface proteins detected were CD4 and CD8 differentiation markers and the T-cell receptor. Extraction of DNA-associated proteins with 0.1N HCl and detergent is necessary for the action of EcoR1 and Exonuclease III, but this treatment destroys phycocyanins and induces cell aggregation, as shown using the doublet-discrimination module. For DNAse I action, cells could be treated with paraformaldehyde and a low concentration of Tween 20, and this treatment was adequate for surface staining preservation (even with phycocyanins) and BrdUrd detection. Both methods were adequate for cell cycle studies, but only 7-amino-actinomycin D could be used as total DNA dye after DNAse action, and good results needed long (48-72 h) incubation in the fixative-detergent mixture. The DNAse I method now allows three-color staining (two surface markers and Brd-Urd), analyzed in a one laser-cytometer for the study of the phenotype of cycling cells, and of their progeny, in vivo and in cell cultures. It also allows the quantitative analysis of cell surface receptor densities in conditions similar to fresh cells.

A novel CD45RA+CD4+ transient thymic subpopulation in MRL-lpr/lpr mice: its relation to non-proliferating CD4-CD8-CD45RA+ tumor cells

MRL-lpr/lpr mice have hypertrophied lymph nodes comprising CD4-CD8- T cells. In addition, they contain CD4+CD8- T cells co-expressing the CD45RA marker. The correlation between these two subpopulations has been difficult to assess. We analyzed the expression of CD45RA (with the RA3-2C2 antibody) in various thymic and peripheral T cell subsets, using three-color immunofluorescence. We showed that in lpr mice (i) a transient CD4+CD8- thymic subset co-expresses CD45RA during the course of the disease, and (ii) thymic as well as peripheral CD4-CD8- and CD4+CD8- T cells brightly express CD45RA; furthermore (iii) in the lymph nodes, during lymphadenopathy, CD4+CD8-CD45RA+ T cells show a broad range of the CD4 fluorescence intensity, and (iv) the increase in MHC class II expression is restricted to CD45RA-T cells of the thymus and lymph nodes of lpr mice. Taken together, these data suggest that the CD4+CD8-CD45RA+ population might generate the CD4-CD8- tumor cells. In addition, using the bromodeoxyuridine labeling technique, we demonstrate that these cells are not the result of increased proliferation.

Thy-1 modulation and cell proliferation at early steps of intrathymic bone marrow cell differentiation

Intrathymic (IT) transfer of bone marrow (BM) precursor cells in sublethally irradiated hosts has been widely used to study T cell differentiation and maturation. In this report we have used double congenic mice Ly 5.1 Thy 1.1 (host) and Ly 5.2 Thy 1.2 (donor) and detected cycling Ly 5.2+ BM cells by in vivo bromodeoxyuridine incorporation, before induction of the Thy 1.2 antigen. Until Day 9 post-transfer, some donor type cells express a high level of Thy 1.2 together with macrophage and granulocyte markers. A few days later, a Thy 1.2low population transiently B220+ was detected. Thereafter, donor type cells expressed an intermediate Thy 1.2 brightness; this population then persisted and surpassed the other subsets. Our findings permitted to establish a relationship between cell cycle and Thy 1 fluorescence intensity according to the sequence: Thy 1low resting, Thy 1low cycling, Thy 1high cycling, Thy 1high resting. Moreover, we have shown that cells from the myeloïd and B lineages can, in vivo, transiently express the Thy 1 antigen, develop and differentiate within the thymus microenvironment.

Routine cytogenetic prenatal diagnosis using dynamic banding (RBG-GBG): a highly reproducible method for amniocytes, fetal cord blood, and chorionic villus investigations

Dynamic banding (RBG-GBG) using pulse 5-bromodeoxyuridine (5-BrdU) incorporation during part of the last S-phase before harvesting has been used in prenatal investigations. This method has already been routinely applied in 1344 cytogenetic investigations. GBG and RBG bandings produced almost identical patterns to classical G- and R-banding methods except for heterochromatic portions and some euchromatic segments. Nevertheless, these discordances may be somewhat helpful for cytogenetic diagnosis (i.e., X numerical abnormalities). The results showed particularly good contrast and staining; 5-BrdU incorporation did not prevent additional staining. Likewise, previous RBG or GBG disclosure allowed further chromosomal identification with C-banding or nucleolar organizer staining. Simplicity and reproducibility were very helpful in cases with a low mitotic index. 5-BrdU had no significant effect on in-vitro damage because only 0.31 percent of cells were affected; so, we believe that dynamic banding should be used more extensively in cytogenetic investigations. Moreover, the staining and contrast qualities were very suitable for automatic methods of analysis now in use: i.e., metaphase finding and computer-assisted karyogram creation.

Prenatal diagnosis of PIBIDS

In a well-documented PIBIDS family, two investigations of DNA excision repair showed a severe defect in lymphocytes from the index case (residual repair activities were 10.6-12.1 per cent). The values for the mother, father, and sister were within the normal range when compared with a healthy control. In the pregnant mother, a prenatal diagnosis of PIBIDS was made by measuring UV-induced unscheduled DNA synthesis in cultivated amniotic fluid cells. Results ranged between 12.5 and 26.1 per cent depending on the UV doses applied and were consistent with an affected fetus. The parents opted for a termination of pregnancy. Following a therapeutic abortion, fetal skin fibroblasts were tested and showed a severe DNA excision-repair defect of 9.2-13.5 per cent of residual activity.

Trisomy 16q23----qter arising from a maternal t(13;16)(p12;q23): case report and evidence of the reciprocal balanced maternal rearrangement by the Ag-NOR technique

We describe a female new-born with partial trisomy of the long arm of chromosome 16. The chromosome anomaly was the result of an unbalanced segregation of a maternal translocation t(13;16)(p12;q23). Dynamic (RBG, GBG) banding and the Ag-NOR technique ascertained the reciprocal balanced maternal translocation between the 16q23----qter and 13q12----pter segments because nucleolar organizers were present on the tip of long arms of the derivative 16 maternal chromosome. As monosomy 13p has little or no deleterious effect we consider our case as exhibiting the phenotype of trisomy 16q23----qter free from any monosomic feature. Clinical effects are of less consequence as compared with previously published cases of partial trisomy 16q.

Accumulation of bromodeoxyuridine-labeled cells in central and peripheral lymphoid organs: minimal estimates of production and turnover rates of mature lymphocytes

Daily lymphocyte production in both central and peripheral lymphoid organs was evaluated by associating in vivo incorporation of bromodeoxyuridine (BrdUrd) with cell surface labeling and multi-parameter flow analysis. At least 10% of mature T and B lymphocytes are generated every 24 h. The kinetic behavior of these cell populations differs, however, in that mature B cells are generated predominantly in the precursor compartments of the bone marrow, while most mature T cell generation occurs at the periphery. Therefore, peripheral expansion is the major mechanism of mature T cell production in the adult mouse. By following the accumulation of BrdUrd-labeled cells in peripheral lymphoid organs we found that the progeny of the daily lymphocyte production was sufficient to renew 30%-40% of all peripheral T and B cells every 48 h, demonstrating a high turnover rate of mature lymphocytes. We also examined the conditions of BrdUrd labeling of cycling cells in vivo. We found that while greater than 90% of bone marrow and thymus cells in S phase were labeled with a single injection of BrdUrd, in peripheral lymphoid compartments 70% of T and B cells in S failed to incorporate BrdUrd. Particular schedules of BrdUrd administration were required to overcome the low labeling efficiency of mature cells in vivo. Prolonged BrdUrd administration, however, had toxic effects on resident cells. The low labeling efficiency of BrdUrd incorporation by mature cells, as well as its potential toxicity during prolonged administration, may explain controversial results obtained by the different strategies used to study lymphocyte population dynamics.

Cell proliferation and differentiation in the fetal and early postnatal mouse thymus

The relationships between cell proliferation and cell differentiation during thymus ontogeny were studied by labeling DNA-synthesizing thymocytes with bromodeoxyuridine and staining with antibodies against CD4, CD8, J11d, phagocytic glycoprotein 1, TCR V beta 8 chain, Thy-1, and IL-2R surface proteins. The development of the thymus was discontinuous, with two well defined growth periods from 13 days to 18 days of fetal life and from 3 days to 6 days after birth, and more progressive growth from day 8 to 2 wk. Cell proliferation started on fetal day 12, 1 day after the arrival of hemopoietic stem cells in the third branchial pouch. These cells were phagocytic glycoprotein 1-positive but IL-2R and Thy-1 negative. Thus, cell proliferation preceded IL-2R expression. Until day 15, CD4-8- thymocytes expanded without differentiation. Then CD4-8+ and CD4+8+ cells appeared; this induction was proliferation dependent and occurred on cells which had already lost IL-2R, but just after maximum expression of this receptor. During several days, the thymus remained of constant size (around 10(7) cells) and behaved like the steady state thymus. On day 3 after birth, expansion started again and was correlated with an increase in CD4-8- proliferation index and IL-2R expression. At the same time, the thymic subset capable of expansion without differentiation was again, transiently, detectable. These results suggest that the inflow of precursor cells into the thymus is permanent but transiently increased at several times during ontogeny. Moreover, the behavior of fetal CD4-8- cells does not appear radically different from that of adult precursors, but the actual difference resides in the variation of the relative proportion of CD4-8- cells at different maturation stages, as revealed by striking variations of IL-2R expression by cycling cells.

Cell proliferation and differentiation in the fetal and early postnatal mouse thymus

The relationships between cell proliferation and cell differentiation during thymus ontogeny were studied by labeling DNA-synthesizing thymocytes with bromodeoxyuridine and staining with antibodies against CD4, CD8, J11d, phagocytic glycoprotein 1, TCR V beta 8 chain, Thy-1, and IL-2R surface proteins. The development of the thymus was discontinuous, with two well defined growth periods from 13 days to 18 days of fetal life and from 3 days to 6 days after birth, and more progressive growth from day 8 to 2 wk. Cell proliferation started on fetal day 12, 1 day after the arrival of hemopoietic stem cells in the third branchial pouch. These cells were phagocytic glycoprotein 1-positive but IL-2R and Thy-1 negative. Thus, cell proliferation preceded IL-2R expression. Until day 15, CD4-8- thymocytes expanded without differentiation. Then CD4-8+ and CD4+8+ cells appeared; this induction was proliferation dependent and occurred on cells which had already lost IL-2R, but just after maximum expression of this receptor. During several days, the thymus remained of constant size (around 10(7) cells) and behaved like the steady state thymus. On day 3 after birth, expansion started again and was correlated with an increase in CD4-8- proliferation index and IL-2R expression. At the same time, the thymic subset capable of expansion without differentiation was again, transiently, detectable. These results suggest that the inflow of precursor cells into the thymus is permanent but transiently increased at several times during ontogeny. Moreover, the behavior of fetal CD4-8- cells does not appear radically different from that of adult precursors, but the actual difference resides in the variation of the relative proportion of CD4-8- cells at different maturation stages, as revealed by striking variations of IL-2R expression by cycling cells.

In vivo dynamics of CD4-8- thymocytes. Proliferation, renewal and differentiation of different cell subsets studied by DNA biosynthetic labeling and surface antigen detection

The proliferative status of CD4-8- thymocyte subsets was determined by in vivo or in vitro labeling with bromodeoxyuridine (BrdUrd), a nonreutilized thymidine analogue detectable with a monoclonal antibody, simultaneously with relevant surface proteins. An actively cycling subset [J11d+, interleukin 2 receptor-positive (IL 2R+)] was defined, besides a relatively resting one (J11d-, Pgp1+, T cell receptor-positive). Continuous per os administration of BrdUrd showed that 85% only of CD4-8- thymocytes were labeled in 6 days confirming the existence of a relatively long-term resting subset. By contrast, CD4+8+ thymocytes were all labeled in 3-4 days. Observation of labeled CD4-8- cells after pulse labeling showed an immediate decrease of their absolute number per thymus, confirming their low autorenewal capacity. However, a small number of labeled cells which were hydroxyurea or colchicine resistant remained CD4-8- for several days and progressively acquired surface expression of IL 2R. IL 2R expression by cycling CD4-8- cells during thymus regeneration after antimitogenic drug treatment was rapid, but very transient. According to these results most CD4-8- thymocytes appear as largely engaged in a proliferation-dependent differentiative process, and do not behave as true stem cells. Consequently, this subset is principally renewed by thymic immigration of exogenously produced resting cells. However, a tenfold expansion of CD4-8- cells was found in the fetal and regenerating thymus, suggesting two proliferative phases during intrathymic CD4-8- cell maturation, the first one yielding to cell expansion and the second to cell differentiation. A tentative evaluation of daily cell immigration is proposed starting with the determination of the number of cells beginning DNA synthesis each day. A global model is finally discussed by confronting our kinetic results with the known reconstitution capacities of CD4-8- thymocyte subsets.

Sequential events in thymocyte differentiation and thymus regeneration revealed by a combination of bromodeoxyuridine DNA labeling and antimitotic drug treatment

The proliferative status of thymocyte cell subsets in vivo was assessed by observing the effect of two antimitotic drugs, hydroxyurea (HU) and demecolcine. Both drugs had the greatest effect on the double-positive (DP) subset followed by the L3T4+ single-positive (SP) subset. However, the decrease in the latter type was delayed by several days, showing that their precursors rather than the cells themselves were killed by HU. Double-negative (DN) cells were less affected, indicating that they contain a resting subset and that they are renewed by emigration rather than by autonomous in situ proliferation. After drug treatment all cycling cells were eliminated from the thymus but, as shown by in vivo and in vitro bromodeoxyuridine incorporation, new cells rapidly reentered in cycle, starting from DN cells and Lyt-2+ SP cells and followed by DP cells. Lyt-2+ SP cycling cells represent an intermediary stage between DN and DP cells, and they are very transient. Injection of HU 24 h after in vivo BrdUrd labeling eliminated most labeled DN cells, but did not prevent the emergence of L3T4+ SP-labeled cells on day 3 as observed in control thymuses. These results suggest that these L3T4+ SP cells are generated from DP cells in the absence of proliferation. Cycling cells in the regenerating thymus were first located at the corticomedullary junction and then in the subcapsular region, suggesting a reverse migration process to that observed after cessation of proliferation. A model is proposed to summarize these sequential events.

Sequential events in thymocyte differentiation and thymus regeneration revealed by a combination of bromodeoxyuridine DNA labeling and antimitotic drug treatment

The proliferative status of thymocyte cell subsets in vivo was assessed by observing the effect of two antimitotic drugs, hydroxyurea (HU) and demecolcine. Both drugs had the greatest effect on the double-positive (DP) subset followed by the L3T4+ single-positive (SP) subset. However, the decrease in the latter type was delayed by several days, showing that their precursors rather than the cells themselves were killed by HU. Double-negative (DN) cells were less affected, indicating that they contain a resting subset and that they are renewed by emigration rather than by autonomous in situ proliferation. After drug treatment all cycling cells were eliminated from the thymus but, as shown by in vivo and in vitro bromodeoxyuridine incorporation, new cells rapidly reentered in cycle, starting from DN cells and Lyt-2+ SP cells and followed by DP cells. Lyt-2+ SP cycling cells represent an intermediary stage between DN and DP cells, and they are very transient. Injection of HU 24 h after in vivo BrdUrd labeling eliminated most labeled DN cells, but did not prevent the emergence of L3T4+ SP-labeled cells on day 3 as observed in control thymuses. These results suggest that these L3T4+ SP cells are generated from DP cells in the absence of proliferation. Cycling cells in the regenerating thymus were first located at the corticomedullary junction and then in the subcapsular region, suggesting a reverse migration process to that observed after cessation of proliferation. A model is proposed to summarize these sequential events.

[Role of RNA in the inactivation of chromosomes during the metaphase]

Unfixed, isolated metaphase chromosomes were used as template in an in vitro RNA synthesis assay. In these conditions, no RNA synthesis was observed by autoradiography. Transcription was effective after treatment with methanol-acetic acid, HCl 0,2 N, NaCl 0,35 M or pancreatic RNase. Transcription is the most important after treatment with RNase. This result points out the problem of the role of RNA in inhibition of chromosome during mitosis.

The respective roles of gallium 67 citrate scanning and diagnostic ultrasound in detecting suppurations in renal allograft recipients

The authors report their experiments relative to the advantage of using gallium 67 scanning in the diagnosis of suppurative lesions in renal allograft recipients. Nineteen cases suggesting abscess were analyzed. In 7 cases in which abnormal isotope uptake was noted, a suppuration was detected in the area where the gallium 67 had accumulated. In 2 cases, the abnormal image corresponded to the location of a healing drained abscess, and, in 1 case of pathological uptake at the level of the graft, it was determined that the cause was chronic rejection without suppurative lesion. In 9 cases in which no abnormal focus of uptake was noted, the symptomatology suggesting abscess was eventually attributed to nonsuppurative causes (rejection, urinary fistula, etc.). It is concluded that gallium 67 scanning is a useful means of detecting suppurations in immunodepressed patients undergoing treatment with steroids which prevent the usual signs of suppuration from appearing. Generally, it can be said that diagnostic ultrasound, performed with respect to the area of abnormal gallium 67 uptake, permits optimum determination of the possibilities of an abscess existing.

[Ultrasonography and radiocholesterol scintigraphy in the topographic diagnosis of a pheochromocytoma (author's transl)]

Topographic diagnosis of adrenal pheochromocytoma were determined by ultrasonography in all 6 cases studied and by radiocholesterol scintigraphy in 6 out of 7 cases studied. It would appear that ultrasonography is preferable in the localization of an abdominal pheochromocytoma, whether adrenal or extra-adrenal. Intravenous urography along with rapid sequence nephrotomography and radiocholesterol scintigraphy, play a complementary role in confirming the topographic diagnosis. In case these methods prove unsuccessful or provide conflicting results, it is then possible to consider computed tomography, angiography and caval catheterization.