CHD5, a brain-specific paralog of Mi2 chromatin remodeling enzymes, regulates expression of neuronal genes

CHD5 is frequently deleted in neuroblastoma and is a tumor suppressor gene. However, little is known about the role of CHD5 other than it is homologous to chromatin remodeling ATPases. We found CHD5 mRNA was restricted to the brain; by contrast, most remodeling ATPases were broadly expressed. CHD5 protein isolated from mouse brain was associated with HDAC2, p66ß, MTA3 and RbAp46 in a megadalton complex. CHD5 protein was detected in several rat brain regions and appeared to be enriched in neurons. CHD5 protein was predominantly nuclear in primary rat neurons and brain sections. Microarray analysis revealed genes that were upregulated and downregulated when CHD5 was depleted from primary neurons. CHD5 depletion altered expression of neuronal genes, transcription factors, and brain-specific subunits of the SWI/SNF remodeling enzyme. Expression of gene sets linked to aging and Alzheimer's disease were strongly altered by CHD5 depletion from primary neurons. Chromatin immunoprecipitation revealed CHD5 bound to these genes, suggesting the regulation was direct. Together, these results indicate that CHD5 protein is found in a NuRD-like multi-protein complex. CHD5 expression is restricted to the brain, unlike the closely related family members CHD3 and CHD4. CHD5 regulates expression of neuronal genes, cell cycle genes and remodeling genes. CHD5 is linked to regulation of genes implicated in aging and Alzheimer's disease.

Measurements of blood flow and histometry of the cellular infiltrate in tuberculin skin test responses of the typical Koch type and the non-turgid variant form (Listeria-type) in pulmonary tuberculosis patients and apparently healthy controls

The typical turgid Koch type and the non-turgid variant form (Listeria-type) of the tuberculin skin test responses were studied in 76 newly diagnosed pulmonary tuberculosis patients and 29 apparently healthy factory worker controls from Surabaya in Indonesia; in general, the patients had more intense responses than the controls. The blood flow velocity (RBCflux) at the centre of the reaction was similar in all groups, but central relative slowing (a presumed forme fruste of severe ischaemia) was much more common in the Koch-type reactions in tuberculosis patients. In both groups of subjects, the overall density of cellular infiltrate (and the major populations of inflammatory cells) was greater in the typical Koch-type reactions than in the non-turgid variant reactions. Thus the Koch-type reactions were indubitably more intense in inflammatory terms than the non-turgid variant form, but the results of this study do not exclude the possibility that there were underlying qualitative differences in pathogenesis between reactions of the two types as well as the obvious difference in severity.

Specificity of antibodies and tuberculin response after occupational exposure to tuberculosis

Specific antibody levels and delayed-type hypersensitivity skin responses to antigens of Mycobacterium tuberculosis in 39 hospital staff who were heavily exposed to tuberculosis (TB) were compared with those in 36 factory employees from Indonesia. Antibody levels to the TB68 epitope of the 14-kDa antigen were significantly greater, while titers to the TB23 (19-kDa) and TB72 (38-kDa) epitopes and lipoarabinomannan (LAM) were lower in exposed than in nonexposed subjects (all P less than .02). The intensity of tuberculin responses correlated positively with anti-LAM and negatively with anti-19-kDa antibody levels. Possible reasons for the selective humoral response of chronically exposed healthy subjects to the 14-kDa antigen, but not to other antigens immunogenic in patients with tuberculosis, are discussed.

Early delayed hypersensitivity responses in tuberculin skin tests after heavy occupational exposure to tuberculosis

The early (six hours) reaction to tuberculin skin testing was studied in 33 Indonesian hospital workers with frequent occupational exposure to M tuberculosis and compared with responses maximal at the usual time (48 hours) in factory workers, from the same locality but with only occasional occupational exposure, to determine the nature of the early reaction. The early reaction had the same general histopathological appearance as that seen in the conventional (48 hour) reaction, and both had an infiltrate consisting largely of T lymphocytes and macrophages. The cell densities were lower in the six hour reactions, but the relative concentration of macrophages was greater in the earlier response. These histometric measurements suggested that the six hour reaction was an accelerated delayed hypersensitivity reaction. Moreover, the absence of a specific IgE response or of particulate masses of Ig or complement, made it unlikely an anaphylactoid or Arthus-type reaction could have been responsible. It is concluded that those with frequent occupational exposure to M tuberculosis have larger numbers of circulating T cells reactive with mycobacterial antigens, so that the development of the skin test response to tuberculin is less dependent on "by-stander" cell infiltration to mediate the delayed hypersensitivity reaction than the reactions in those with less intense and less frequent natural exposure. The skin test response maximal at six hours is probably a hyperimmune reaction to an antigen recognised by T cells.

Histometric studies on cellular infiltrates of tuberculin tests in patients with sarcoidosis

The density and microanatomical location of CD4 and CD8 lymphocytes and of monocytes/macrophages at the site of a tuberculin test were measured in 13 patients with sarcoidosis, and the results were compared with those seen in a group of healthy controls. The cellular infiltrate was significantly reduced in the sarcoid subjects compared with the controls for all cell phenotypes studied; the ratio of CD4 positive:CD8 positive lymphocytes was significantly increased in the sarcoid group. Clinically negative reactions showed substantial numbers of infiltrating mononuclear cells, although not as great as in clinically apparent reactions. A clinically negative tuberculin reaction does not necessarily imply anergy to the test substance and should not be termed "negative".

Histometric studies on biopsies of tuberculin skin tests showing evidence of ischaemia and necrosis

In a study of tuberculin skin tests in 216 consecutive untreated pulmonary tuberculosis patients, one showed central necrosis at 48 h: there was no effective blood flow at the centre of this lesion, but the periphery was markedly hyperaemic. Many dermal capillaries and venules contained deposits of fibrin, but none was occluded completely: the surviving cells in the dermal infiltrate were almost all macrophages. Five patients with strongly positive reactions at 48 h showed slower blood flow at the centre of the reaction than at the periphery (central relative slowing, CRS), possibly indicating central ischaemia short of necrosis: no fibrin deposits were seen in the dermal vessels of these skin test sites. The cellular infiltrate in the dermis was similar in distribution, but more abundant than that seen in uncomplicated positive reactions of comparable clinical size and with blood flow velocity maximal at the centre. At 48 h, lymphocytes were more numerous than macrophages in both groups, CD8 lymphocytes were more abundant in CRS reactions, but CD4 and CD25 (activated) T-lymphocytes and macrophages had a similar density in both groups. Epidermal CD1 cells were less frequent in CRS reactions than in uncomplicated positive reactions. Although CRS reactions showed more intense inflammation than the uncomplicated controls, none of the histometric measurements correlated with the extent of CRS. Follow-up studies showed that CRS reactions reverted to a normal hyperaemic blood flow pattern 5 days after antigen injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Histometric studies on cellular infiltrates of tuberculin tests in patients with haemophilia

The number of microanatomical location of CD4 and CD8 lymphocytes, of cells bearing receptors for I12 and transferrin, and of monocyte/macrophages in the dermis at the site of a tuberculin test were measured in 13 patients with haemophilia (10 seronegative and three seropositive for human immunodeficiency virus (HIV]. The overall density of lymphocytes in the perivascular and diffuse parts of the infiltrate was similar to that reported in other groups of subjects without evidence of immunosuppression. The CD4:CD8 ratio of the infiltrating lymphocytes throughout the section showed an inverse relation with clotting factor consumption. There was no significant change in the CD4:CD8 ratio in the diffuse infiltrate at various levels into the dermis in tuberculin reactions in patients with haemophilia, unlike healthy controls and other groups with no evidence of immunosuppression, who have previously been shown to have increasing CD4:CD8 ratio with increasing depth into the dermis. The number of cells bearing receptors for I12 and transferrin and of monocyte/macrophages was related to total lymphocyte density in the infiltrate. There was no evidence of serious impairment of the cell mediated response to a long term recall antigen, but the relatively low preponderance of CD4 lymphocytes in the diffuse infiltrate, particularly in the deeper dermis, may be the earliest indicator of impending immunosuppression.

The relation between cutaneous blood flow and cell content in the tuberculin reaction

The relationship of velocity of blood flow to density and microanatomical distribution of inflammatory cells in the dermis was studied in 20 human tuberculin tests. Most positive reactions showed maximal blood flow velocities (measured as red blood cell (RBC) flux) at the centre of the reaction, but the two most intense responses showed 'central relative slowing' (CRS) with higher RBC flux at the periphery. Two of the four clinically negative reactions showed a considerable acceleration of blood flow, but the other two showed no such acceleration. The packing density of lymphocytes/monocytes in the perivascular zone was greater in the stronger positives than in the weaker reactions. The density of cells in the intervening dermis was markedly lower than in the foci: the lesions with CRS had the highest density of cells in the diffuse infiltrate of the reticular dermis. At the centre of the reaction, blood flow velocity was generally related to density of cellular infiltrate, except in those with CRS, which had a disproportionately lower blood flow velocity. The finding that the circulatory adaptation to a delayed hypersensitivity reaction can be inadequate may explain the dermal acidosis previously observed in intense skin test reactions, and may be the underlying mechanism of necrosis in hypersensitivity reactions.

Diversity in migration of CD4 and CD8 lymphocytes in different microanatomical compartments of the skin in the tuberculin reaction in man

The lymphocytes in the perivascular foci of tuberculin skin tests have a similar CD4:CD8 ratio to those in the peripheral blood, suggesting that these subsets do not show bias in their initial emigration. By contrast, the diffusely infiltrating lymphocytes show a relative preponderance of CD4 cells which is progressively greater in successive 250 micron layers into the dermis. A generally similar pattern is seen in healthy controls and in patients with untreated pulmonary tuberculosis, treated leprosy, haemophilia A and chronic obstructive lung disease (COLD) patients treated with prednisolone, but the gradient of increasing CD4:CD8 ratio with depth into the dermis is significantly less steep in patients with tuberculosis, haemophilia and prednisolone-treated COLD than in the healthy controls. Selective migration results in a relative preponderance of CD4 cells in the diffuse infiltrate and it is suggested that this is a mechanism likely to potentiate defensive reaction to Mycobacterium tuberculosis: any deficiency in selective migration may make immunological defences less effective and so contribute to the chronicity of the lesions of tuberculosis.

Blood flow velocity in cutaneous lesions of leprosy

The velocity of blood flow in the cutaneous lesions of leprosy was measured by the noninvasive technique of laser-Doppler velocimetry in nine male patients, all under treatment with World Health Organization multidrug regimens. In three patients with stable borderline tuberculoid (BT) lesions, the blood-flow velocity was slightly faster over the lesion than that in adjacent uninvolved skin. There was no substantial difference between different sites at the center and edge of individual lesions in each patient, but there was some variation between subjects. In one other BT patient with a reversal reaction, blood-flow velocity was 20-fold greater than in adjacent uninvolved skin. In four patients with stable borderline lepromatous/lepromatous (BL/LL) disease, the blood-flow velocity was 3 to 9 times faster over the plaques than in adjacent skin. There was relatively little difference between measurements over comparable points at the edge and center of individual plaques, or between plaques in the same patient, but there were considerable differences between patients. A fifth BL patient in reversal reaction showed generally similar results to those found in the stable BL/LL patients. Histometric study of the biopsies taken immediately after blood-flow measurement from two different plaques on each of four BL patients showed a clear relationship between the granuloma fraction measured by planimetry and the blood-flow velocity. This finding suggests that laser-Doppler velocimetry might prove to be a useful, clinically acceptable, noninvasive technique for monitoring the severity of hyperemia as an early indication of reversal reaction during chemotherapy trials in leprosy patients.

Changes in activation markers and cell membrane receptors on human peripheral blood T lymphocytes during cell cycle progression after PHA stimulation

Phytohaemagglutinin (PHA)-stimulated peripheral blood lymphocytes were examined sequentially for changes in volume, the appearance of cell membrane receptors and nucleic acid synthesis. The kinetics of appearance of activation antigens were compared with the progress of the cell through the separate events of volume growth and nucleic acid syntheses, to determine points at which regulation of receptors may control further progress through the cell cycle. In all samples tested there was a consistent pattern of response in the proportion of cells progressing through the cell cycle. Most of the T cells increased in size (mean 82% at 24 hr), fewer cells entered the Gla/Glb phase with the onset of RNA synthesis (mean 68% at 48 hr) and even fewer entered DNA synthesis (mean 42% at 72 hr). The time-course of appearance and the number of cells expressing IL-2 receptors were almost identical with that of cells responding by RNA synthesis. A similar correlation was observed between expression of the transferrin receptor and DNA synthesis. Addition of anti-Tac antibody temporarily suppressed the onset of RNA synthesis and antibodies to the transferrin receptor suppressed DNA synthesis. These linkages are further evidence that IL-2 and transferrin are the specific signals for cellular RNA and DNA synthesis. With optimal concentrations of PHA, addition of IL-2 did not increase the proportion of cells bearing activation antigens or undergoing nucleic acid synthesis. Suboptimal concentrations of PHA produced a small reduction in the number of cells expressing the IL-2 receptor, but a much greater reduction in the rate of entry into RNA synthesis. There was a consistent increase in all activation parameters tested with the addition of IL-2, but the proportion of cells expressing the transferrin receptor and entering DNA synthesis was consistently lower than that of cells that expressed the IL-2 receptor or entered RNA synthesis. This suggests that regulation of the IL-2 receptor is not responsible for the reduction in the number of cells that proceed to proliferation. The CD2 antigen (T11(1] showed increasing expression in a step-wise fashion after activation, the increases coinciding with the onset of RNA and DNA syntheses.

Characterization of a factor in leprosy serum that inhibits the growth of mitogen-stimulated normal human lymphocytes

A factor that inhibits the growth of mitogen-stimulated lymphocytes from normal donors has been detected in the sera of patients with chronic leprosy. The inhibitory activity was detected with similar frequency in patients with tuberculoid or lepromatous leprosy, although higher levels of activity were detected in the latter. The factor reduced the growth in volume of the lymphocytes in the first 24 hr after stimulation, the synthesis of RNA during the first 3 days of culture and the replication of DNA in 72-hr cultures. All the inhibitory activity co-purified with IgG on gel filtration, ammonium sulphate fractionation and ion exchange chromatography. The activity was stable to heating at 56 degrees but labile at 100 degrees and was absorbed from serum or from purified IgG preparations by staphylococcal protein A. On gel filtration of the sera on Sephadex G-200, none of the activity appeared in the void volume, indicating that it is not due to immune complexes. We conclude that the activity is due to an IgG antibody and suggest that it is an autoantibody since the sera inhibited the growth of all donor lymphocytes tested.

Mechanisms by which barbiturates suppress lymphocyte responses to phytohaemagglutinin stimulation

Certain barbiturates (the intermediate- and short-acting drugs) reduce the growth of PHA-stimulated peripheral blood mononuclear cells, but phenobarbitone (a long-acting drug) is ineffective: replicative growth is more sensitive than activation. This action is associated with a marked reduction in the density of interleukin-2 receptors on the cell membrane and of the numbers of cells expressing them, but the growth rate cannot be restored by supplementation of the tissue culture medium with exogenous interleukin-2. The affected cells show swelling of the mitochondria and cytoplasmic fat globules: the presence of residual bodies and myelin figures indicate an increase in the rate of degradation of organelles. There was no appreciable increase in the number of necrotic cells seen on electron microscopy of cultures exposed to high concentrations of thiopentone or other potent barbiturates, but the presence of debris in the DNA cytogram at 72 h indicated some increase in the death rate of cells exposed to the growth suppressing barbiturates. It would be inadvisable to administer these short- and intermediate-acting barbiturates over long periods, particularly at high dosage, because of the potential danger of iatrogenic immunosuppression.

Suppression of growth of PHA-stimulated human lymphocytes by a novel steroid (RU 28 362) lacking the 21-OH group

RU 28 362 is a novel synthetic steroid (lacking the 21-OH group) which reacts exclusively with the glucocorticoid receptor. It is therefore chemically different from the other natural and synthetic glucocorticoids in common use which also bind to a lesser extent to receptors for other classes of steroids. Aspects of the immunosuppressive effect of RU 28 362 were studied by comparing its suppressive effects on PHA-stimulated growth of human lymphocytes with those of hydrocortisone, betamethasone and the inactive analogue, 21-deoxyhydrocortisone. RU 28 362 was more potent than either hydrocortisone or betamethasone, but all three glucocorticoids had a parallel dose-response curve in suppression of the increase in cell volume that occurs with activation during the first day in culture. In studies on the time of appearance and density of IL-2 receptors during the first 3 days in culture, RU 28 362 was also somewhat more inhibitory and had a steeper dose-response curve than hydrocortisone or betamethasone. RU 28 362 was much more inhibitory and had a steeper dose-response curve than either hydrocortisone or betamethasone in inhibiting [3H]-TdR incorporation by 3-day PHA stimulated cultures. 21-deoxyhydrocortisone did not inhibit any aspect of PHA-stimulated lymphocyte growth.

Skin test responsiveness to four new tuberculins in patients with chronic obstructive airways disease receiving short term high doses of, or long term maintenance treatment with, prednisolone: clinical appearances and histometric studies

The response to skin testing with tuberculins extracted from various species of mycobacteria was studied in 49 patients from Dundee with chronic obstructive airways disease. Seventeen had never been treated with steroids (group 1), 17 were receiving short term high doses of prednisolone (group 2) and did not have impaired Synacthen tests; 15 were receiving long term maintenance treatment and did have impaired Synacthen tests (group 3). Erythematous and indurated reactions were seen in a few patients, more commonly to antigens from Mycobacterium tuberculosis than to the other species: neither of the latter treatment groups showed appreciable reduction in reactivity compared with that of the group 1 patients. The number and microanatomical distribution of the T4 and T8 lymphocytes and the M3 bearing monocytes and macrophages was studied immunocytochemically in cryostat sections of biopsy specimens from the antigen injection sites. The density of these cells was significantly less in clinically negative reactions than in those with erythema or induration, but was unrelated to the presence or absence of a history of treatment with prednisolone. The T4:T8 ratio in the section as a whole was similar to that of the peripheral blood, but T8 cells were relatively more common in the perivascular and periappendicular foci, and T4 lymphocytes were predominant in the diffuse component of the infiltrate. I12 receptor bearing lymphocytes were uncommon: such cells were least common in the clinically negative reactions, but the number and distribution were apparently unrelated to the presence or absence of prednisolone treatment. It was concluded that currently accepted regimens of treatment with prednisolone did not reduce the effector arm of type IV (delayed type hypersensitivity) responses and so are unlikely to compromise this aspect of protective immunity.

The cellular responses of tuberculosis and leprosy patients and of healthy controls in skin tests to 'new tuberculin' and leprosin A

The density and distribution of T4 and T8 lymphocytes and of monocyte/macrophages at the site of skin tests with mycobacterial antigens was studied in pulmonary tuberculosis and leprosy patients and in healthy controls. Most of the inflammatory cells were located in perivascular and periappendicular foci in the dermis: the percentage of the dermis occupied by focal infiltrate was unrelated to the clinical measurement of the area of induration. There was a less intense diffuse infiltrate in the dermis between the foci, most marked in the papillary dermis and lessening progressively in deeper layers. In patients, diffusely infiltrating lymphocytes were more numerous (mainly due to an excess of T8 cells) in relation to extracts of the pathogen causing their disease than to extracts of the other organism: T8 cells were particularly numerous in reactions to Leprosin A in three of four partly treated leprosy patients who had been classified as tuberculoid at the time of diagnosis. The density of diffusely infiltrating macrophages showed a similar density gradient and selective concentration in response to active disease pathogens. However these cells were less numerous in partly treated leprosy patients than in controls and most frequent in untreated pulmonary tuberculosis patients. Selective migration of monocyte/macrophages and, to a lesser extent T8 cells, appears to be a prominent feature in the reaction of patient with active mycobacterial disease to antigens derived from the causative organisms: this suggests that it might become possible to distinguish direct reactions from cross-reactions in human delayed hypersensitivity reactions by identification of these histological features.

T4 lymphopenia in patients with active pulmonary tuberculosis

The numbers of cells bearing the T3 (pan-T cell), the T4 (putative helper/inducer cells), the T8 (putative suppressor/cytotoxic cells) and B cell phenotypic markers were counted in venous blood samples from 26 newly diagnosed pulmonary tuberculosis patients and 29 healthy controls from East Java. The absolute T cell count was lower in the patients and T4 cells were fewer in patients (mean 748/mm3) than in controls (mean 1,043/mm3), but there were no significant differences in total T8 cell and B cell counts between patients and controls. The T4:T8 ratio was not disturbed in many patients, but it was less than 1.6 in 11 of 26 patients and in only three of 29 controls: this ratio was less than 1.2 (the lower limit of 'normal') in six patients but no controls. The intensity of the T4 lymphopenia was unrelated to the extent of the lesion seen radiologically or the size of the skin test reaction to PPD. Levels of interferon-alpha were not elevated in the serum of any of the patients or controls. It is suggested that the T4 lymphopenia was a reaction to the mycobacterial infection and not a manifestation of underlying secondary (acquired) immune deficiency.

Histometric study of the localisation of lymphocyte subsets and accessory cells in human Mantoux reactions

Intradermal injection of purified protein derivative produced typical delayed type hypersensitivity reactions in five healthy human subjects. The major subpopulations of lymphocytes and certain accessory cells were located in frozen sections of biopsies of the lesions with monoclonal antibodies and immunohistochemical staining. The densities (expressed as number/unit area for comparison) of the different types of cells were counted at various microanatomical locations in the tissue. The inflammatory cells were concentrated in narrow zones, initially (24 h) only surrounding small blood vessels but later (48-96 h) also around sweat ducts. Lymphocytes were the predominant cell type at these sites with T4 and T8 cells randomly intermixed at a ratio similar to that in the mononuclear cell fraction of the peripheral blood samples removed at the time of biopsy. There was also a scanty diffuse infiltrate in the intervening dermis, but here the T4:T8 ratio was significantly lower than that in the peripheral blood or perivascular cuffs. There was considerable intersubject variation in the relative preponderance of T8 cells in the diffuse infiltrate. The results suggest that there is no subset selection in the initial emigration of lymphocytes through vascular endothelium in the delayed hypersensitivity reaction, but that the subsets behave differently during the subsequent migration through the tissues. It remains to be determined whether the extent to which T8 cells migrate more rapidly than T4 cells through the tissues may influence the reaction at the site of entry of organisms or antigens into the body by altering the balance of the immunoregulatory lymphocyte subsets. This may underlie some of the differences in susceptibility to infection between subjects and determine the type of granuloma that develops in a particular patient.

The destruction of peripheral-blood lymphocytes by extracorporeal exposure to ultraviolet radiation

Venous blood from healthy adult human donors was circulated through a wholly extracorporeal circuit for periods up to 140 min without apparent damage to the lymphocytes. However, when the blood was exposed to short-wave ultraviolet radiation (UVC; lambda, 254 nm), separated mononuclear cells showed a depressed response to mitogen stimulation: the magnitude of this effect was related to the duration of exposure. This depression cannot be attributed to change in blood pH, partial pressures of oxygen and carbon dioxide, temperature of cell trauma. Plasma from irradiated blood was less satisfactory than non-irradiated plasma for the support of growth of phytohaemagglutinin-stimulated lymphocytes in culture, probably because of depletion of essential nutrients, and there was little evidence for the generation of growth-inhibitory humoral factors. The UVC-irradiated lymphocytes had normal ultrastructure when removed from the extracorporeal circuit, but underwent apoptosis and necrosis during the first day of tissue culture with or without mitogen stimulation.

Some tetracycline drugs suppress mitogen-stimulated lymphocyte growth but others do not

Eight tetracycline drugs were tested for inhibitory effect on phytohaemagglutinin (PHA) stimulated growth (measured by [3H]-TdR uptake) of peripheral blood mononuclear cells: at least 26 normal subjects were tested with each drug. Doxycycline reduced DNA synthesis appreciably at concentrations within and just above the therapeutic range of blood levels: it was the most potent inhibitor, but demeclocycline, methacycline and minocycline had similar, if less potent, effects. Tetracycline, oxytetracycline, chlortetracycline and clomocycline did not inhibit DNA synthesis of 3-day cultures even at concentrations five to ten times greater than the therapeutic blood level. Volume spectroscopy measurements showed that none of the eight tetracycline drugs interfered with the recruitment of cells into G1-phase growth of the first cell cycle after PHA stimulation.

In vitro effects of doxycycline and tetracycline on mitogen stimulated lymphocyte growth

Doxycycline and tetracycline were tested for inhibitory effect on PHA stimulated growth (measured by [3H]-TdR uptake) of peripheral blood mononuclear cells from 26 normal subjects. Doxycycline reduced DNA synthesis appreciably at concentrations within and just above the therapeutic range of blood levels: tetracycline did not inhibit DNA synthesis of 3 day cultures even at concentrations five-10 times greater than the therapeutic blood level. Detailed studies on the action of doxycycline by volume spectroscopy and RNA flow cytofluorimetry indicated that this drug did not influence the recruitment of cells into the first G1-phase. Cell counts, DNA flow cytofluorimetry and autoradiography after pulsed exposure to [3H]-TdR showed a reduction in the numbers of growing cells in 2 and 3 day cultures in the presence of doxycycline compared with those containing tetracycline at the same concentration.

The sensitivity of peripheral blood lymphocytes to growth inhibition by hydrocortisone is not determined by their OKT4:OKT8 ratio

Normal adult human subjects show considerable variation in sensitivity to depression of the activation phase of mitogen-induced lymphocyte growth by the natural glucocorticoid, hydrocortisone. In a study of 21 subjects, the slope of the log-dose response to hydrocortisone was unrelated to the relative numbers of cells in the two major T-cell subpopulations stained by the OKT4 and OKT8 monoclonal antibodies. It is concluded that the extent of the glucocorticoid-induced suppression of early mitogen-stimulated lymphocyte growth is probably not determined by relative numbers of the various immunoregulatory lymphocytes.

Effect of anaesthesia and surgery on the pre-S-phase cell cycle kinetics of mitogen-stimulated lymphocytes of previously healthy people

The influence of general anaesthesia, and of operative surgery, on immune responsiveness was studied in blood obtained from 26 women undergoing laparoscopic sterilization (minor operation group) and in 14 women undergoing abdominal hysterectomy (major operation group). Since immunity depends ultimately on clonal expansion of lymphocytes, the growth potential of peripheral blood lymphocytes was studied in tissue culture by mitogen stimulation. There was no evidence of any change in either the number of responding cells (those that have left the resting G0-phase and responded to mitogen stimulation by entering the G1-phase of the first cycle of growth) or in the rate at which cells grow in volume during the period of study. It was concluded that there was no evidence that anaesthesia, or surgery, impaired this aspect of the immune response in our patients, but the design of the experiments does not allow comment on other aspects of the immune response such as antigen presentation, immunoregulation and effector mechanisms, which are superimposed on the basic clonal expansion mechanisms studied in this investigation. Incidentally, we noted that the standard method for isolation of lymphocytes from peripheral blood frequently yielded highly contaminated preparations: if this fallacy was not appreciated, tests with contaminated lymphocytes could be misinterpreted as showing depression.

Mitogen-stimulated lymphocyte growth and chronic uraemia

Lymphocytes were isolated from venous blood by the Böyum method from 36 patients with chronic renal failure: the preparations were more frequently and more heavily contaminated with non-lymphoid cells than the equivalent preparations from normal controls. Volume spectroscopy measurements showed that, in the samples without gross contamination, lymphocytes from uraemic subjects react to mitogen stimulation with normal pre-S-phase cell-cycle kinetics. In other experiments, plasma from uraemic patients was shown to be more potent than serum in inhibiting the growth of mitogen-stimulated lymphocytes from normal subjects, both in the first G1-phase and in replicative growth. Thus humoral suppression appears to be more important than a cellular defect in explaining the depressed responses of uraemic blood to mitogen stimulation.

Mitogen stimulation of peripheral blood lymphocytes of duodenal ulcer patients during treatment with cimetidine or ranitidine

During a double-blind randomised clinical trial of cimetidine and ranitidine in the management of duodenal ulcer, the response of patients' peripheral blood lymphocytes to optimal mitogenic stimulation in vitro has been measured. Treatment with cimetidine, but not ranitidine, was associated with a significant increase in the proportion of peripheral blood lymphocytes responding to this optimal mitogenic stimulation. We conclude that these effects of cimetidine may not be mediated at classical histamine H2-receptors.

Mechanisms of phytohaemagglutinin (PHA) stimulation of normal human lymphocytes: 'trigger' 'push' or both?

The growth in volume of human peripheral blood lymphocytes after stimulation with various concentrations of PHA was measured with an electronic particle counter. The percentage of growing cells and averaged values describing their growth rates during the elapsed period of culture were estimated by fitting to the observed data the volume distributions derived from a mathematical model. With sub-optimal doses, the percentage of cells stimulated , and their incremental growth rate, increased with increasing dose of PHA, but the time-course of recruitment into the G1-phase was similar with all PHA concentrations studied. The results provide strong support for the 'trigger' hypothesis that there is a distribution of stimulation thresholds within the lymphocyte population: consequently, increasing mitogen concentration will be expected to result in increased numbers of responding cells within the suboptimal concentration range.

Serum inhibitory factor in lepromatous leprosy: its effect on the pre-S-phase cell-cycle kinetics of mitogen-stimulated normal human lymphocytes

The sera of ten Egyptian man with long-standing lepromatous leprosy (LL) (mean duration 17.4 years) that had failed to respond to dapsone treatment were shown to inhibit mitogen stimulation responses of normal human lymphocytes. When first tested, the sera partly inhibited the response to phytohaemagglutinin (PHA) and pokeweed mitogen and virtually abolished that to concanavalin A (Con A): after repeated freezing and thawing, the Con A inhibition had disappeared, whereas the PHA response was still partly inhibited. The inhibitory serum factor(s) had similar actions on lymphocytes from each of six normal donors. Although the sera varied in potency, they showed similar dose-response curves when tested against lymphocytes from a single donor. The principal action of the sera was to reduce the number of cells responding to mitogen, without modifying the kinetics of recruitment or rate of volume growth during G1-phase in those cells that were unaffected by the inhibitory substances(s). Study of PHA dose-response curves and of the effect of delayed addition of LL serum suggested that the serum factor(s) act by diminishing the responsiveness of the cells, rather than by reducing the concentrations of free mitogen or by blocking cell membrane mitogen receptors. The serum from one apparently healthy attendant, who had nursed leprosy patients for 30 years but who did not have leprosy or other chronic infective disease, inhibited completely stimulation by all three mitogens in a manner different from that of LL sera. Serum from the other 13 control patients did not modify the response of normal lymphocytes to stimulation by any of the three mitogens studied. It was concluded that the inhibitory factor(s) in the serum of patients with LL were a consequence of the disease and not of the environment in which the patients lived. Microscopy confirmed that the techniques used for recovery of the cultured cells did not introduce bias into the volume spectroscopy measurements.

The effect of strenuous physical exercise on circulating blood lymphocytes and serum cortisol levels

Venous blood was removed from healthy subjects immediately before and at intervals after exercise on a bicycle ergometer. Immediately after exercise, the subjects developed a lymphocytosis in which (a) the E-rosette percentage fell by 10% but their absolute number in the circulating blood rose by more than 70%, (b) the percentage of PHA-stimulated cells fell, but their absolute numbers increased considerably and (c) the absolute numbers of Con A- and PWM-responding cells increased. The numbers of lymphocytes in the various subpopulations had returned virtually to the pre-exercise levels 15 minutes after stopping exercise. During the response to exercise, the characteristics of the cells in the various subpopulations did not show any major changes, despite considerable and rapid fluctuations in numbers: it is suggested that exercise discharges intravascularly sequestered cells and that cortisol may be involved in re-sequestration of stress-released cells. It is recommended that, in clinical studies on circulating lymphocyte numbers and populations, the patient should be rested for at least 15 minutes before venesection.

A simple method for determining the extent of cellular contamination in peripheral blood lymphocyte preparations

A method is described for calculating, from the size distribution of the cells, the extent of cellular contamination of lymphocyte concentrates prepared from venous blood. The precision of this method was checked by direct comparison with differential leucocyte counts obtained by direct microscopy on 29 samples chosen because they showed a wide range of intensity of contamination. By virtue of its technical simplicity, the method has proved useful in a diagnostic service laboratory for checking the purity of lymphocyte preparations either before performing lymphocyte function tests or after a period of 24 h in tissue culture.

A new method for semi-automated quantitation of E-rosettes using a particle size analyser (Coulter Channelyzer)

Visual counts of the number of SRBC attached to individual lymphocytes in E-rosette preparations from 3 healthy young adults were made by 3 experienced observers: from these data the size distribution profile of particles in each E-rosette preparation was calculated. In parallel experiments the size distribution profile was measured directly with a particle size analyser (Coulter Counter and Channelyzer): in every case the observed profile lay within the 95% confidence band around the reconstructed profiles. It was concluded that the Coulter Channelyzer profile is an accurate measurement of the E-rosette size distribution and that particle sizing could provide a reasonable basis for semi-automated tests for E-rosettes. A mathematical model has been developed by which the percentage of lymphocytes forming E-rosettes, the distribution of number of attached SRBC and the average avidity of the lymphocyte receptor for SRBC could be deduced from the size-distribution profiles. The method has a high degree of precision, and a good correlation (P less than 0.01) was obtained when the percentage of E-rosettes (defined for this purpose as having three or more attached SRBC) obtained from the new method was compared with results from standard light microscopy.

A new method of testing for mitogen-induced lymphocyte stimulation: measurement of the percentage of growing cells and of some aspects of their cell kinetics with an electronic particle counter

Human lymphocytes were cultured with or without added PHA for periods not exceeding one day so that none of the cells had entered the first mitotic division. The size distribution of the cells was measured with an electronic particle counter and the results were collected in a multichannel analyser. An iterative stochastic model was developed to estimate the proportion of responding cells and their growth characteristics. This mathematical model was based on a few simple assumptions about the pattern of cell growth and was considered to fulfill basic requirements of plausibility and parsimony. The technique described in this paper makes measurement of the absolute percentage of responding cells and their average growth rate in mitogen-induced lymphocyte stimulation tests possible in routine diagnostic laboratories for the first time.

A method for standardised resuspension of lymphocyte E-rosettes

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T-cell lymphoma of the thyroid

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