FK506 and cyclosporin A each inhibit antigen-specific signaling in the T cell line 171 in the absence of a calcium signal

Antigen-specific signal transduction leading to IL2 induction and secretion in the T cell line 171 is augmented by association of p56lck with CD4. Although no change in cytoplasmic calcium level ([Ca2+]i) was detectable during antigen-specific signal transduction of 171-CD4+ cells, IL2 induction was inhibited by FK506 and CsA. Since these drugs are thought to act selectively by inhibiting calcineurin, a calcium-calmodulin-dependent protein phosphatase associated with activation of the IL2 promoter, we considered the possibility that calcineurin is constitutively active in 171 cells. However, we found no evidence for this because PMA failed to supplement any putatively active calcineurin to induce IL2 secretion. We suggest that IL2 secretion induced by antigen presentation to TCR/CD4/p56lck requires an FK506 and cyclosporin A-sensitive step which may be independent of calcium signaling. Rapamycin did not inhibit IL2 secretion induced by TCR/CD4/p56lck, emphasizing the specific action of FK506 and cyclosporin A.

Rat liver blood flow after ischemia and reperfusion. The effects of the platelet-activating factor antagonist WEB-2170 and of removing circulating leukocytes

The inflammatory response to trauma induces release of platelet activating factor (PAF), which promotes leukocyte adherence to the vascular endothelium. Ischemia and reperfusion induces inflammatory reactions that play a role in reperfusion injury, and here we investigate the role of both PAF and of leukocytes in damage to reperfused rat liver. The experimental procedure consisted of the temporary interruption of blood flow to the left lateral and medial lobes of the rat liver in vivo, and subsequent reperfusion after defined periods. Rats were pretreated either with the PAF-antagonist WEB-2170 or with vinblastine to induce leukopenia, and compared with controls. The postischemic liver blood flow and liver oxyhemoglobin saturation were recorded using an He-Ne Laser doppler flowmeter and photometer. Reperfusion after 30 and 45 min of ischemia was associated with partial recovery to normal values and was inversely proportional to the duration of ischemia. In the WEB-2170-treated group, liver flow and hemoglobin saturation upon reperfusion did not show significant differences when compared with the untreated control groups, suggesting that inhibition of PAF activity did not protect against the microcirculatory disturbance induced by ischemia and reperfusion in the liver. In contrast, rats made leukopenic by treatment with vinblastine showed significantly better recovery of blood flow and hemoglobin saturation than the control group after 45 min of ischemia. Thus, we found that although PAF alone did not appear to have a pivotal role in the cascade of reperfusion injury, the effect of leukocytes is critical.

Serum PAF-acetylhydrolase in severe renal or hepatic disease in man: relationship to circulating levels of PAF and effects of nephrectomy or transplantation

(1) PAF-acetylhydrolases form a major pathway for the degradation of platelet-activating factor (PAF). Here we investigate the role of the kidney and the liver in the control of PAF-acetylhydrolase levels by comparing normal subjects to patients with abnormal liver or kidney function. These patients had either severe chronic liver disease, chronic renal failure or were anephric. In a few cases PAF was also measured. (2) In those patients where PAF was measured there was no evidence that circulating PAF levels determined PAF-acetylhydrolase release. (3) In anephric patients serum PAF-acetylhydrolase levels were normal or even raised. Therefore the kidney is unlikely to be the usual major source of serum PAF-acetylhydrolase in man. (4) Liver patients with chronic cholestasis had elevated serum PAF-acetylhydrolase especially in stage III or IV primary biliary cirrhosis, as well as in a patient with secondary biliary cirrhosis and one with cholangiocarcinoma. Since normalisation of liver function following liver transplantation was accompanied by a reduction to normal or near normal PAF-acetylhydrolase levels, it is likely that the liver can play an important role in regulating levels of this enzyme in serum.

Monoclonal antibodies that define canine homologues of human CD antigens: summary of the First International Canine Leukocyte Antigen Workshop (CLAW)

A panel of 127 monoclonal antibodies against canine leukocyte antigens, including controls, was distributed to 29 laboratories that performed a variety of experiments to identify groups of antibodies against the canine equivalents of some of the human CD antigens. Cluster analysis was performed centrally, using the submitted antibody binding data from immunofluorescence, ELISA and immuno-histology experiments. Immunoprecipitation for molecular weight determination was also performed centrally with T-cell blasts and a B-cell line as the sources of antigen. Clusters of three or more antibodies were found that defined the canine equivalents of the CD5, CD4, CD8 and Thy-1 antigens, and these could be used to label T-cell subsets from the peripheral blood. Other groups of monoclonal antibodies recognized the canine homologues of the CD11/18 group of antigens, CD44 and the CD45/CD45R antigen family: these should be useful in isolating functional subsets of CD4+ helper T cells. There was a cluster of four antibodies that bound strongly to platelets (probably CD41 antigen), three antibodies that were specific to B cells (including CD21) and two antibodies against a granulocyte antigen (possibly CD15). A number of reagents were found against canine MHC-II and immunoglobulin, with some of the latter able to distinguish between Ig subclasses. Properties of each of the canine antigens defined by these monoclonal antibodies are discussed and compared with other species. The availability of such a panel of reagents should allow rapid improvements in the immunological diagnosis of canine disease, and there might now be a potential for testing novel therapeutic strategies in a clinical veterinary setting.

Prodigiosin 25C: effect in in vitro models for T cell activation and T cell cycling and in vivo for rat heart allografts

Prodigiosin 25C inhibited both lymphocyte activation (concanavalin-A-activated mouse spleen cells) and constitutive cell cycling of T cells and fibroblasts. This suggests that prodigiosin 25C is not selective for activation of T lymphocytes as has been previously reported. Use of prodigiosin 25C to suppress allograft rejection of rat hearts (DA to PVG) showed that 1 mg/kg/day i.p. had no effect whilst 10 mg/kg/day i.p. was toxic as manifest by weight loss and diarrhoea at 3 days. Although this toxicity was reversible upon reversion to 1 mg/kg/day, no major prolongation in allograft survival was seen. Our data suggests that prodigiosin 25C has a low therapeutic index and may not be selective for T cell activation.

Inhibition of the serine/threonine protein phosphatases PP1 and PP2A in lymphocytes: effect on mRNA levels for interleukin-2, IL-2R alpha, krox-24, p53, hsc70 and cyclophilin

Lymphocyte activation requires signal transduction mediated by reversible phosphorylation. Changing profiles of phosphorylated intermediates relate to the progressive series of transduction pathways in cells moving from G0 to G1, and thereafter through the cell cycle. We have previously shown that transient inhibition of the serine/threonine protein phosphatases PP1 and PP2A by okadaic acid enhances early mitogenic stimulation. Thus target proteins of PP1/PP2A may be involved in regulation of early mitogenic signalling, with the phosphorylated form(s) being associated with signal enhancement. Later, pathways require dephosphorylation of these proteins, since continuous treatment with okadaic acid blocks lymphocyte progression through the cell cycle. Delayed addition of okadaic acid showed that this blockade occurs between 8 and 24 hr. Here we have furthered these observations to the level of gene induction by measuring messenger RNA (mRNA) levels for the following proteins: interleukin-2 (IL-2) and IL-2R alpha; p53, a tumour suppressor protein; the transcription factor krox-24; and two mediators of protein folding, namely cyclophilin and the heat-shock protein hsc70. An external standard was used to quantitate the mRNA levels per cell. We found that 24 hr exposure to okadaic acid has a general suppressive effect on concanavalin A (Con A)-stimulated gene induction. However, at 4 hr okadaic acid enhanced IL-2 mRNA levels induced by Con A. Moreover, in unstimulated lymphocytes, okadaic acid caused the induction of krox-24, indicating a role for PP1 and PP2A in the regulation of this gene in resting cells.

Tolerance in the mouse to major histocompatibility complex-mismatched heart allografts, and to rat heart xenografts, using monoclonal antibodies to CD4 and CD8

Mice given a single short course of anti-CD4 and anti-CD8 monoclonal antibodies (mAb) became tolerant of major histocompatibility complex (MHC)-incompatible vascularized heart allografts in a donor- and organ-specific manner. T cell depletion was not important, as blocking antibodies were equally effective. Anti-CD4 antibody therapy alone was sufficient to establish tolerance. Anti-CD8 mAb therapy alone was associated with poor recipient survival, although survivors were rendered tolerant. A second donor-type heart allograft to the neck was always accepted in recipients which had carried the first abdominal heart allograft for over 120 days, with the first heart also continuing to function. However, donor-type skin grafted at 100 days was sometimes rejected, albeit chronically. Those recipients that accepted the donor-type skin were able to reject third-party skin grafts mismatched at the MHC, or over multiple minor differences alone. Thus, the tolerance induced appeared to be donor and tissue specific, although spreading in some cases to tolerance of skin. Similarly donor-specific tolerance was found when xenogeneic PVG rat hearts were grafted into CBA/Ca mice using the same protocols of anti-CD4 plus anti-CD8 mAb. Resolution of the mechanisms underlying these forms of tolerance may permit the design of improved immunosuppressive protocols for human organ transplantation.

FK506 and rapamycin: differential sensitivity of human, baboon, cynomolgus monkey, dog and pig lymphocytes

It has recently been suggested that there are species differences in the sensitivity of T lymphocytes to the immunosuppressive effect of FK506. We explore this phenomenon further and compare FK506 with rapamycin in lymphocytes from dog, pig, baboon, cynomolgus monkey and man. We found that the relative sensitivity of T cells to FK506 did not necessarily correlate with their sensitivity to rapamycin, further emphasising the different mode of action of each drug. The serum may alter results of dose-response curves, and thus autologous serum may introduce an uncontrolled variable when different species are being compared in vitro. We conclude that the differences in sensitivity of lymphocytes from various species to FK506 and rapamycin are independent of each other, and these differences are likely to reflect variation in the overall interactive pathways involved in T-cell mitogenesis.

Serum levels of Mullerian inhibiting substance in boys with cryptorchidism

Serum levels of Mullerian inhibiting substance (MIS) were measured in boys with cryptorchidism (n = 104) and paired, age-matched controls (n = 104) using an enzyme immunoassay. Control MIS levels were high during the first year of life with a peak level at 4 to 12 months, subsequently diminishing with age. MIS levels in patients with undescended testes also declined with age, although a surge was not found in the first year. Mean MIS concentration of cryptorchid boys was significantly lower than controls (P less than .001). There was a significant reduction of the mean MIS level in children with bilateral cryptorchidism compared with those with unilateral undescended testis (P less than .05). These differences might support the hypothesis that MIS initiates transabdominal testicular descent. However, because most undescended testes are probably the result of anatomical or functional abnormalities during transinguinal testicular descent, differences in MIS levels more likely result from secondary testicular degeneration. In the future, MIS immunoassay should play an important role in the investigation of gonadal function in boys with various genital disorders, including cryptorchidism.

Phosphatases PP1 and PP2A act after the G0/G1 interface in lymphocyte activation

An understanding of the progressive events required for lymphocyte activation is a prerequisite to understanding the molecular mechanism of immunosuppressive reagents, and is of central relevance to autoimmunity and immune tolerance. Although reversible phosphorylation is a major control mechanism in T cell activation, few facts are known about phosphatases in T cells. It has recently become possible to block selectively the serine/threonine specific protein phosphatases PP1 and PP2A by okadaic acid, a C38 polyether fatty acid produced by dinoflagellates. Here we have used this new and powerful biochemical probe to identify and quantify the activities of PP1 and PP2A at various times during lymphocyte activation. The selected model was mouse T cell activation by concanavalin A because this gave a reproducible experimental system that allowed large scale experiments in defined, serum-free conditions. Our results show the following: (1) levels of PP1 and PP2A in lymphocytes appear to be unusually low, effects being measured at 10 nM okadaic acid compared to 1 microM reported for other cell types; (2) the okadaic acid effect was readily reversible; (3) okadaic acid stimulated mitogenesis when present in early G1 but inhibited mitogenesis in late G1; (4) levels of PP1 and PP2A remained relatively constant over the first 7 h following stimulation; (5) lymphocytes activated in the presence of okadaic acid became resistant to subsequent treatment with FK506; and (6) combined or consecutive treatment with okadaic acid and FK506 resulted in additive drug effects. We conclude that PP1 and PP2A are not involved in the G0-G1 transition as defined by the FK506-sensitive step.(ABSTRACT TRUNCATED AT 250 WORDS)

The nasopharynx and under-aeration of the middle-ear

This study compared nasopharyngeal sepsis with under-aeration ear disease. Nasopharyngeal sepsis was assessed by culture taken directly from the surface of removed adenoid tissue. 156 cases were studied; 100 showed varying degrees of middle-ear under-aeration and 56 had no active ear disease or history of it. In addition, an assessment of post-nasal obstruction was made and this too was compared with middle-ear status. The conclusions suggested that, whilst normal ears can exist in the presence of accepted nasal pathogens, diseased ears are rarely seen in the absence of nasal sepsis. The degree of post-nasal obstruction seemed irrelevant. The commonest nasopharyngeal pathogen was Haemophilus influenzae and when found alone this had a particularly detrimental affect on middle-ear aeration, causing a significant incidence of mucoid middle-ear effusion in this group.

Simple method of monitoring colonising microbial load in chronic bronchial sepsis: pilot comparison of reduction in colonising microbial load with antibiotics given intermittently and continuously

Aerobic and anaerobic culture of sputum on selective bacteriological media, combined with a new method of plating and plate reading, permitted rapid identification and quantitation of three genera of bacteria commonly associated with chronic bronchial sepsis (Haemophilus spp, Pseudomonas aeruginosa, and Staphylococcus aureus) and avoided time consuming serial dilution of sputum and subculture of organisms. The accuracy of this new technique was assessed in patients with chronic bronchial sepsis and was used to detect changes in the colonising microbial load of Haemophilus spp and Ps aeruginosa in patients with bronchiectasis receiving one of three different antibiotic regimens: intermittent seven day courses of amoxycillin for exacerbations; or a six month course of continuous oral or nebulised amoxycillin. The colonising microbial load of Haemophilus spp was reduced only temporarily (+++ to ++) after each intermittent course of antibiotic, but a sustained and greater reduction in the colonising microbial load of both Haemophilus spp (+++ to +) and antibiotic resistant P aeruginosa (+++ to +) was seen during both continuous treatments. Sputum purulence decreased in parallel with colonising microbial load, reflecting a reduction in host inflammatory response to the colonising microbial load.