The role of tumor rejection antigens in host antitumor defense mechanisms

BACKGROUND

Normal cells undergo contact inhibition of growth when their surface molecules interact. Tumor cells, however, have undergone a mutation that prevents this arrest of growth upon contact inhibition and allows constant growth. Thus, growth inhibition fails to occur despite the interaction of surface molecules. In recent years a subgroup of these surface molecules has been of interest to cancer investigators. This subgroup has been termed the tumor rejection antigens (TRAs). As the name implies, these are specific to the tumor of origin and may direct the immune system of the host to target the tumor cells and kill them.

METHODS

A literature search was carried out on TRAs to ascertain the current thinking on the subject.

RESULTS

Initial studies of TRAs have revealed that some of them may be heat shock proteins (HSPs). In particular, grp96, a number of the HSP90 family, has been implicated. More recent studies, however, have shown that HSPs alone may not be immunogenic but may act as carrier proteins for tumor specific peptides.

CONCLUSION

Such findings have led to speculation that HSPs or their associated peptides may have a role in the diagnosis and/or treatment of specific cancers. Immunotherapy and bispecific antibodies in particular are areas in which HSPs may prove to be useful.

Antigen presentation in protein-energy malnutrition

Protein-energy malnutrition is associated with intrinsic defects in macrophage (MO) microbicidal function, but effects on MO-CD4+ cell interaction are unclear. This study examined the effect of protein-energy malnutrition on components of Ag presentation (AP) by peritoneal macrophages (PMO) and splenocyte responses (MLR) in the naive (resident) and infected state (mycobacterium-BCG), and assessed the potential role of prostaglandin (PGE2) and L-arginine-derived nitric oxide (NO) as regulatory mechanisms in these immune interactions. Mice were randomized to receive either a control (24% casein, RD) or low-protein (2.5% casein, LPD) diets for 8 weeks. PMO and splenocytes were harvested and AP function and MLR assessed +/- NG-mono-methyl-L-arginine (NMMA; competitive inhibitor of NO. synthesis) or indomethacin (PGE2 inhibitor). PMO components of AP were evaluated, including phagocytic function, MHC-class II (Ia) expression, and interleukin-1 (IL-1) and interleukin-6 (IL-6) production. PGE2 production and NO. (measured as NO-2) synthesis were also assessed. AP and MLR were preserved in protein-energy malnutrition in both resident and activated states. BCG infection in RD was associated with PMO activation as measured by increased O-2 and NO-2 release, but impaired AP and MLR responses. NMMA and indomethacin enhanced AP and MLR in RD groups only. Individual components of PMO AP (phagocytosis, IL-1 and IL-6 production) were defective during protein-energy malnutrition, as were NO-2 and PGE2 production. Thus, AP and MLR were preserved in LPD groups which may be related to a loss of prostaglandin- and L-arginine-mediated suppressor mechanisms.

Failure of macrophage activation in experimental obstructive jaundice: association with bacterial translocation

Bacterial translocation from the gastrointestinal tract and macrophage activation are central to current theories of sepsis. The relevance of both in obstructive jaundice is unclear. The effect of bile duct ligation for 7 days on bacterial translocation to mesenteric lymph nodes and on macrophage activation in a rat model was examined. Compared with an incidence of zero in sham-ligated controls, bile-duct ligated rats had a 67 per cent incidence of Gram-negative colonization of mesenteric lymph nodes. This was associated with a significant (P < 0.001) decrease in macrophage tumour necrosis factor, superoxide anion and nitric oxide production compared with that in sham controls. Spontaneous bacterial translocation occurs in experimental obstructive jaundice and is associated with marked suppression of macrophage activation. This suggests a mechanism whereby jaundiced patients may be more susceptible to persistent infection but relatively protected against uncontrolled sepsis.

Immune function in patients undergoing open vs laparoscopic cholecystectomy

BACKGROUND

Abnormal release of inflammatory mediators following surgical injury is associated with immunological alteration, which may predispose to sepsis. Laparoscopic surgery is associated with reduced postoperative complications, but mechanisms are unclear. We hypothesized that early recovery following laparoscopic surgery may relate to minimal impairment of immune function.

DESIGN

Analysis of the temporal immune responses in two similar groups of patients randomized to open (n = 22) vs laparoscopic (n = 22) cholecystectomy. Patients were matched for age, height, weight, and operation time. Immune parameters, including monocyte superoxide anion (O2-) and tumor necrosis factor release, neutrophil O2- levels and chemotaxis, total white blood cell counts, partial arterial oxygen pressure, and serum cortisol and C-reactive protein levels were assessed preoperatively and on postoperative days 1 and 3.

RESULTS

There were significant increases (P < .001) in monocyte release of O2- and tumor necrosis factor, neutrophil release of O2- and chemotaxis, and white blood cell count in the open vs laparoscopic cholecystectomy study groups, with a concommitant decrease in partial arterial oxygen pressure. These findings correlated with significantly higher postoperative septic complications in the open cholecystectomy group (P < .05). There were no significant differences in either plasma cortisol or C-reactive protein levels between groups. All measurements were carried out in a blinded fashion.

CONCLUSIONS

This study demonstrates that laparoscopic surgery appears to be associated with similar metabolic responses compared with open surgery, while immune parameters vary greatly between groups. The beneficial effects of laparoscopic surgery may relate, in part, to preservation of immune function in the postoperative period.

Laparoscopic excision of a patent urachus

We report the case of a patent urachus presenting as an umbilical discharge. The urachus was visualised laparoscopically, divided at either extremity, and successfully removed with subsequent abrogation of symptoms.

Nitric oxide (endothelium-derived relaxing factor) attenuates revascularization-induced lung injury

Aortic occlusion and revascularization (I-R) may lead to lung injury dependent on activated neutrophil adherence. Nitric oxide (NO) inhibits neutrophil adherence to endothelial cells. We studied the effect of increasing or decreasing NO levels with sodium nitroprusside (SNP) or N-nitro-L-arginine methyl ester (L-NAME) in an I-R lung injury model of 30 min ischemia followed by 120 min reperfusion. Sprague-Dawley rats (10/group) were randomized to controls, I-R, I-R treated with L-NAME (10 mg/ml/hr), and I-R treated with SNP (0.2 mg/ml/hr). Myeloperoxidase activity (MPO) was used as a measure of pulmonary neutrophil influx. Pulmonary endothelial permeability was measured by wet:dry weight ratio and bronchoalveolar lavage protein (BAL prot) and neutrophil counts (BAL PMN). Aortic occlusion and revascularization led to significant increases in pulmonary neutrophil influx (6.1 +/- 0.1 MPO u/g vs 3.05 +/- 0.4 MPO u/g in the control group, P < 0.001) and microvascular leakage; BAL prot (347 +/- 32 mg/ml in controls vs 454 +/- 16 mg/ml in the I-R group, P < 0.05); and BAL PMN (0.7 +/- 0.05 in controls vs 1.8 +/- 0.07 PMN/ml in the I-R group, P < 0.001). These changes were exacerbated further by administration of L-NAME (MPO = 8.9 +/- 0.7; BAL prot = 581 +/- 40 mg/ml; BAL PMN = 2.7 +/- 0.16 PMN/ml). Sodium nitroprusside therapy attenuated the I-R-induced lung injury (3.5 +/- 0.4 MPO u/g, P < 0.05 vs I-R; BAL prot = 330 +/- 61 mg/ml; BAL PMN = 0.9 +/- 0.1 PMN/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Role of endotoxin in mononuclear phagocyte-mediated inflammatory responses

Lipopolysaccharide (LPS), which is derived from the cell wall of gram-negative and some gram-positive bacteria, plays a major role is the pathogenesis of septic shock. Initiation of these responses depends on LPS interaction with a number of immune cells, not least the mononuclear phagocyte (MP). Mononuclear phagocytes bind the LPS/lipopolysaccharide-binding protein complex through the CD14 receptor and thus mediate the release of a wide range of inflammatory mediators. Release of these mediators is teleologically beneficial but under certain circumstances may be detrimental, resulting in the systemic inflammatory response syndrome. The development of this syndrome is not clearly understood but appears, in part, to be dependent on the ability of the host to respond to these mediators. This review evaluates the mechanisms of LPS-MP interaction and the therapeutic strategies aimed at inhibiting this interaction.

Beneficial effects of taurolidine in experimental pancreatitis

Taurolidine has potent antiendotoxin and antimicrobial effects in vitro. This study assessed the effect of taurolidine in a well-described model of acute pancreatitis. Ninety-five male Wistar rats (250 g) were studied. Pancreatitis was induced by intraductal injection of 50 microliters of a 4% sodium taurocholate solution at a pressure of 25 cm water. Animals were randomly allocated to 1 of 10 groups: 4 groups were used to characterize the model and there were 6 treatment groups. Taurolidine (100 mg/kg) or saline was administered intravenously at Time 1, 4 hr, or 4 and 24 hr following induction of pancreatitis. Serum amylase, endotoxin levels, and blood cultures were assessed at 4 and 24 hr. Survival was documented at 1 week. Serum amylase levels were elevated in animals in whom acute pancreatitis was induced; however, there was no difference in serum amylase between animals treated with taurolidine and those treated with saline. Positive blood cultures were more numerous in saline-treated groups. Treatment with taurolidine was associated with significantly (P < 0.01) lower endotoxin levels (14 +/- 8 pg/ml) compared with saline-treated animals (350 +/- 87 pg/ml). Taurolidine administration significantly improved survival compared with controls, when given at 4, 24, and 4/24 hr postinduction of pancreatitis (P < 0.05). Taurolidine was beneficial in this model of acute pancreatitis.

Granulocyte-macrophage colony-stimulating factor inhibits tumour growth

The effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on murine antitumour responses was examined. Sixty mice received Lewis lung carcinoma implants and were then randomized to receive GM-CSF 1 microgram/day, GM-CSF 0.5 microgram/day or saline for 10 days and studied with regard to tumour volume, carcass weight and food intake. Macrophage antitumour mechanisms including oxygen free radical production and nitric oxide release were studied in peritoneal macrophages after co-culture with GM-CSF in vitro and in vivo. GM-CSF 1 microgram/day decreased tumour growth after 5 days (mean(s.e.m.) 0.62(0.14) versus 1.24(0.19) cm3, P = 0.017). GM-CSF upregulated macrophage antitumour mechanisms by enhancing the in vivo production of superoxide radicals (mean(s.e.m.) 0.69(0.06) versus 0.45(0.10) nmol, P < 0.05) and nitric oxide (mean(s.e.m.) 48(3) versus 24(4) mumol, P < 0.01). GM-CSF functions through the enhancement of macrophage tumoricidal activity, suggesting a therapeutic potential for this cytokine in the tumour-bearing host.

Safety of double-stapled anastomosis in low anterior resection

Clinical leakage of the anastomosis follows low anterior resection for rectal carcinoma in 5-10 per cent of patients despite standard stapling techniques. A modification of this method has obviated the need for a distal purse string. A flexible transverse stapling instrument (Roticulator 55) is applied across the rectum below the tumour, and a double-staggered row of staples is inserted as a substitute for the distal purse string. End-to-end stapled anastomosis is then performed with peranal insertion of a Premium CEEA stapling instrument. In 111 patients the indications for operation were colorectal carcinoma (96 patients), diverticulosis (ten), megarectum (four) and ulcerative proctocolitis (one). Three patients had clinical evidence of anastomotic leakage; all survived. The incidence of radiological leakage on Gastrografin enema 10-12 days after operation was 9 per cent. The perioperative mortality rate was 2 per cent; all deaths were from cardiovascular causes. Local recurrence of tumour occurred in eight patients (7 per cent) after a mean follow-up of 40 months. In conclusion, double-stapled end-to-end anastomosis has made low anterior resection for rectal carcinoma a safe procedure with a low mortality rate, an acceptable local recurrence rate and minimal (clinical) anastomotic leakage.

Splenectomy predisposes to fungal sepsis through defective phagosome formation

Postsplenectomy septic sequelae may be fatal, but the mechanisms are unclear. We hypothesized that peritoneal macrophage (PM phi) antimicrobial function is abnormal following splenectomy and that this may predispose to increased mortality from the fungal pathogen Candida albicans. Study 1 (in vivo): female CD-1 mice were randomized into control (C), laparotomy (L), or laparotomy+splenectomy (L + S) and inoculated with C. albicans (10(7) organisms, ip) and were studied for mortality. Study 2 (in vitro): mice were randomized to C, L, or L + S groups. Twenty-four hours later, PM phi were harvested and studied for their antifungal activity, including percentage PM phi ingestion of C. albicans and vacuolar sealing of C. albicans within PM phi, percentage C. albicans killing, and superoxide anion (O2-) generation, the mechanism by which candida are killed. Results showed decreased phagocytosis and killing of C. albicans in the L + S group (P < 0.05 vs C) and reduced vacuolar sealing (P < 0.05 vs C) but significantly higher O2- release compared to that in other groups (P < 0.05). Mortality in the L + S group from C. albicans sepsis was significantly higher than that in the other groups (60% compared to 20% in the L group and 13% in C, P < 0.02). This may have resulted from L + S-induced defective phagocytosis of C. albicans and depressed C. albicans killing but increased O2- release in response to candida. This discrepancy between decreased killing and increased O2- may result from increased leakage of O2- from more unsealed vacuoles in the L + S group. Thus, L + S may predispose to candida-induced mortality through defective PM phi intracellular candida killing while enhancing the release of O2- extracellularly from unsealed vacuoles, causing tissue injury.

Macrophage-dependent candidacidal mechanisms in the murine system. Comparison of murine Kupffer cell and peritoneal macrophage candidacidal mechanisms

Candida albicans infection is common in immunocompromised patients. The role of fixed tissue macrophages (M phi), including Kupffer cells (KC) and peritoneal macrophages (PM phi), in host defense against C. albicans is unclear. This study examined murine M phi candidacidal mechanisms and evaluated the in vitro role of the macrophage-activating factor IFN-gamma in augmenting these mechanisms. The effect of in vivo administration of IFN-gamma on survival after lethal C. albicans challenge in the murine system was also assessed. Percent PM phi and KC ingestion of C. albicans were similar. Prior opsonization of Candida increased the percentage of M phi ingestion of this pathogen. PM phi and KC phagocytic function was similar for both nonopsonized and opsonized C. albicans, but KC demonstrated markedly decreased ability to kill this pathogen (O2-, Candida killing). IFN-gamma enhanced KC and PM phi candidacidal activity. PM phi and KC Ag presentation was increased in early Candida infection, but diminished in established infection, when the majority of animals died. C. albicans failed to elicit significant amounts of either IL-1 or TNF compared with LPS stimulation of PM phi and KC in vitro. IFN-gamma treatment in vivo was associated with significantly improved survival (p &lt; 0.01).

Macrophage-dependent candidacidal mechanisms in the murine system. Comparison of murine Kupffer cell and peritoneal macrophage candidacidal mechanisms

Candida albicans infection is common in immunocompromised patients. The role of fixed tissue macrophages (M phi), including Kupffer cells (KC) and peritoneal macrophages (PM phi), in host defense against C. albicans is unclear. This study examined murine M phi candidacidal mechanisms and evaluated the in vitro role of the macrophage-activating factor IFN-gamma in augmenting these mechanisms. The effect of in vivo administration of IFN-gamma on survival after lethal C. albicans challenge in the murine system was also assessed. Percent PM phi and KC ingestion of C. albicans were similar. Prior opsonization of Candida increased the percentage of M phi ingestion of this pathogen. PM phi and KC phagocytic function was similar for both nonopsonized and opsonized C. albicans, but KC demonstrated markedly decreased ability to kill this pathogen (O2-, Candida killing). IFN-gamma enhanced KC and PM phi candidacidal activity. PM phi and KC Ag presentation was increased in early Candida infection, but diminished in established infection, when the majority of animals died. C. albicans failed to elicit significant amounts of either IL-1 or TNF compared with LPS stimulation of PM phi and KC in vitro. IFN-gamma treatment in vivo was associated with significantly improved survival (p < 0.01).

Let the finger linger

Retrorectal masses are rare and of insidious onset. We report a consecutive series of six such cases (males = 4, females = 2). The main presenting complaint was back pain and the most reliable physical sign was a palpable mass posteriorly on rectal examination (all cases). C T scan was the most radiologically informative investigation. Surgical intervention was undertaken using both anterior (trans-abdominal) and posterior (retrorectal) approaches. The majority of the masses excised were benign and all patients, to date, remain well.

Perioperative nutrition in cancer patients

Cancer patients have the highest incidence of protein-calorie malnutrition seen in hospitalized patients, with significant malnutrition occurring in more than 30% of cancer patients undergoing major upper gastrointestinal procedures. Clinically significant malnutrition occurs as a result of diminished nutrient intake, increased nutrient losses, and tumor-induced derangements in host metabolism. In the absence of adequate exogenous nutrients, the body utilizes endogenous substrates to satisfy the ongoing requirements of both host and tumor for energy and protein. In those patients with malignant obstruction of the gastrointestinal tract, the tumor itself may induce diminished nutrient intake. Present day treatment modalities including gastrointestinal resection, chemotherapy, and radiotherapy compound these metabolic derangements, further increasing the risk of postoperative morbidity and death. The presence of malnutrition in cancer patients has prognostic importance. In a review of more than 3000 cancer patients, DeWys and colleagues identified significantly improved survival in those patients without weight loss compared with those had lost 6% of their body weight (Am J Med 69:491-497, 1980). Other investigators have noted increased postoperative morbidity and mortality associated with malnutrition. Early hypotheses suggested that reversal of weight loss would improve survival. The development and refinements of enteral and parenteral nutrition have provided the opportunity for studying the relationship between nutritional supplementation and postoperative prognosis. Nutrition support is therefore often instituted to improve nutritional status and thereby reduce the risks of postoperative complications. This article addresses the beneficial role of preoperative nutrition therapy in cancer patients.

Cytokines in tumour therapy

Cytokines are low molecular weight proteins released by cells of the immune system that have therapeutic potential in cancer. They include the interleukins, the interferons, tumour necrosis factor and the colony-stimulating factors. Cytokines are capable of producing significant and sustained responses against a number of tumours. Clinically, the highest response rates to cytokine immunotherapy have been seen in melanoma and renal cell cancer. Current efforts aim to reduce treatment-related toxicity while maintaining the efficacy of cytokines. The therapeutic potential of these agents may be increased with genetic manipulation by introducing genes encoding cytokines into tumour-infiltrating lymphocytes and certain tumour cells. However, immunotherapy remains time consuming and expensive, and further developments are necessary before it can have a definitive role in tumour management.

Effects of laparotomy on systemic macrophage function

Surgical trauma induces immunosuppression that may adversely influence survival. This study examined the effect of laparotomy on two different macrophage populations, peritoneal macrophages (PM phi) and Kupffer cells. Female, 6- to 8-week old, CFW/C3H-HeN mice (n = 160) were randomly allocated to one of three study groups: control, ether anesthetic only, or ether anesthetic and laparotomy. On postoperative days 1 and 3, PM phis and Kupffer cells were harvested and assayed for superoxide anion production (O2-), percent macrophage phagocytosis of Candida albicans (CAP), percent C. albicans killed by macrophages (CAK), percent major histocompatibility complex (MHC)-class II antigen expression, and antigen presentation. Macrophages isolated on postoperative day 1 were also cocultured with 100 units/10(6) cells/ml interferon-gamma (IFN-gamma). Laparotomy significantly impaired microbicidal activity (O2-, percent CAP, and percent CAK) and antigen presentation on postoperative day 1. On postoperative day 3, O2- and antigen presentation were increased significantly (p less than 0.05) over control values, indicating a rebound phenomenon. Kupffer cell microbicidal function was unchanged on postoperative days 1 and 3. The initial immune impairment (PM phis: O2-, CAP, and CAK) was abrogated by IFN-gamma treatment. In immunosuppressed hosts after injury, administration of macrophage-activating factors such as IFN-gamma could be of therapeutic benefit.

Anti-neoplastic effects of interleukin-4

Interleukin-4 (IL-4) is a cytokine, with potential anti-neoplastic effects. This study examined the effects of IL-4 on host anti-tumor responses in a murine model. C57/B16 mice (n = 40) were randomized to receive Lewis lung carcinoma (10(6) cells: right flank; sc) or saline, and sacrificed 10 days postinoculation for assessment of peritoneal macrophage (PMO) anti-tumor mechanisms [superoxide anion generation (O2-), tumor necrosis factor (TNF), and TNF-independent (P815) cytotoxicity], splenocyte mixed lymphocyte response (MLR) (Balb/c stimulator), and cytotoxic lymphocyte generation (CTL against P815). Cells were cultured +/- IL-4 (100 U/ml). In a second study, 20 mice received Lewis lung implants (sc) and were randomized on Day 21 to receive daily IL-4 (1000 U/mouse; ip) or saline. Tumor volumes and median survival were assessed. Tumor necrosis factor-independent cytotoxicity (O2-, MLR and CTL) was impaired in the tumor-bearing (TB) study group. Interleukin-4 administered to cultured cells from TB mice enhanced O2-, as well as MLR and CTL (P less than 0.01), and decreased TNF release but did not alter PM phi TNF-independent anti-tumor responses (P815). In vivo administration of IL-4 significantly decreased tumor growth (P less than 0.05) after 10 days of treatment and significantly prolonged median host survival (P less than 0.05). These findings indicate the therapeutic potential of IL-4 in the TB host which may function through downregulation of TNF production while potentiating certain T cell-dependent and independent anti-tumor immune mechanisms.

Interleukin 1 and its relationship to endotoxin tolerance

Endotoxin (lipopolysaccharide [LPS])-induced cytokine release has been implicated in the pathogenesis of sepsis. Sublethal doses of LPS induce tolerance to a septic insult. This study evaluated pretreatment with interleukin 1 (IL-1) against an LPS challenge and examined its relationship to endotoxin tolerance. C3H/HeN mice (N = 100) were injected intraperitoneally with phosphate-buffered saline (control group), IL-1 (200 micrograms/kg), or LPS (1 mg/kg) for 3 days. On day 5, peritoneal macrophages were harvested and assayed for antimicrobial activity (superoxide anion production and Candida albicans phagocytosis). Serum cytokine levels and survival after an LPS challenge on day 5 were also assessed. Pretreatment with IL-1 or LPS significantly increased superoxide anion production, C albicans phagocytosis, and survival compared with pretreatment with phosphate-buffered solution. Interleukin 6 levels significantly decreased in the IL-1 and LPS groups. Peak levels of tumor necrosis factor significantly decreased only in the LPS group. Thus, pretreatment with IL-1 or low doses of LPS may exert protective effects by decreasing levels of interleukin 6 while increasing antimicrobial activity. Mice pretreated with IL-1 were protected from endotoxin despite elevated peak levels of tumor necrosis factor, suggesting a different mechanism for endotoxin tolerance than for tolerance to tumor necrosis factor.

Impairment of macrophage activation and granuloma formation by protein deprivation in mice

Protein-calorie malnutrition predisposes to infection by intracellular pathogens, but the basis for this predisposition is unclear. We studied the effect of protein deprivation on mouse peritoneal macrophage function and on granuloma formation during infection by bacille Calmette-Gueŕin (BCG). Injection of lipopolysaccharide (LPS) to induce inflammation elicited fewer peritoneal cells from mice fed a 2.5% protein diet than from mice fed an isocaloric chow in which protein calories constituted 24% of the total. LPS-elicited macrophages from protein-deprived mice demonstrated a reduction in spreading, total cell protein, cell lactate dehydrogenase, and release of superoxide anion (O2-) in response to stimulation. Priming in vitro by interferon (IFN)-gamma for enhanced release of O2- was also significantly impaired in protein-deprived mice. This defect was reversible by repletion with 24% protein diet for 10 days. Impairment of macrophage function in protein-deprived mice was further evidenced by an impaired capacity to express Ia antigen in response to IFN-gamma and by reduced production of IL-1 activity in response to LPS. Infection by BCG in protein-deprived mice was characterized by impaired granuloma development in liver, lungs, and spleen. Thus, in this model, protein deprivation significantly impaired macrophage activation, as assessed by morphologic, metabolic, and functional criteria. This impairment might compromise immune effector mechanisms dependent on macrophage activation, including rejection of intracellular pathogens.

Enhancement of interleukin-2 immunotherapy with L-arginine

Nutrient substrates have been shown to enhance cell-mediated immunity, but their role as adjuvants to immunotherapy has not been previously determined. This study evaluated L-arginine as an essential substrate for optimal generation of lymphokine-activated killer (LAK) cells. This experiment also assessed supplemental dietary L-arginine as a means to potentiate the host antitumor response to interleukin-2 (IL-2) in a murine neuroblastoma (NRB) model. A/J mice received 1% arginine or isonitrogenous 1.7% glycine in addition to a regular diet 14 days before subcutaneous inoculation with C1300 NRB cells. Twenty-four hours later, animals received low (1 x 10(6) U/kg three times a day) or high (3 x 10(6) U/kg three times a day) doses of IL-2 or saline intraperitoneally for 4 days. On days 4 and 10 post-C1300 NRB inoculation, mice were killed for assessment of natural killer cell and tumor specific cytotoxicity. Remaining animals were followed for tumor incidence, tumor growth, and duration of host survival. Interleukin-2 therapy in mice receiving dietary arginine compared with those receiving glycine resulted in significantly augmented natural killer cell cytotoxicity (day 4) and generation of specific tumoricidal mechanisms (day 10). The addition of dietary arginine to low-dose IL-2 therapy significantly diminished C1300 NRB engraftment (p less than 0.05) and growth (p less than 0.001) and prolonged the duration of host survival (p less than 0.05) compared with the glycine treatment group. In vitro studies demonstrated that L-arginine is an essential substrate for optimal generation of LAK cells. Thus, supplemental dietary L-arginine enhances lymphocyte cytotoxic mechanisms and potentiates IL-2 immunotherapy.

Inhibition of macrophage-activating cytokines is beneficial in the acute septic response

Interferon-gamma and other cytokines enhance macrophage (M phi) antimicrobial function and have been considered for therapeutic use in sepsis. Systemic sequelae of macrophage activation, however, are unclear. This study examined the effects of M phi activating cytokines (interferon-gamma [IFN-gamma] and interleukin-4 [IL-4]) and monoclonal antibodies directed against these cytokines in modulating the acute septic response. CFW/Swiss Webster mice (n = 345) received endotoxin (lipopolysaccharide [LPS]: 60 mg/kg body weight intraperitoneally) and were randomized to five treatment groups: IFN-gamma (10(4) units), IL-4 (10(4) units), IgG1 isotype antibody (TRFK5: 200 micrograms), anti-IFN-gamma (200 micrograms), or anti-IL-4 (200 micrograms) monoclonal antibodies (MAbs) given simultaneously or 2 hours after LPS. Animals were divided into two groups and studied for mortality or measurement of peritoneal M phi superoxide anion release (O2-), tumor necrosis factor (TNF), and IL-6 production 6 hours after administration of LPS +/- experimental regimens. Serum TNF and IL-6 also were assessed at 2 and 4 hours after LPS, respectively. Administration of LPS resulted in a 27% survival compared with 10% in the IFN-gamma and 13% in the IL-4 groups. Treatment with anti-IFN-gamma offered protection against LPS lethality (93%-100% survival, p less than 0.001 vs. other groups) when given either simultaneously or 2 hours after LPS. Anti-IFN-gamma also significantly decreased PM phi O-2 and TNF release. Thus anti-IFN-gamma may have an important role in the modulation of the acute septic response.

Harry M. Vars Research Award. Arginine supplementation improves histone and acute-phase protein synthesis during gram-negative sepsis in the rat

Mechanisms of nutrient alteration of hepatic protein synthesis during sepsis are unclear. In vitro, arginine downregulates endotoxin-stimulated hepatocyte protein synthesis but in vivo effects are unknown. This study evaluated the effects of supplemental arginine or glycine on fibrinogen (acute-phase protein), histone, albumin, and liver protein synthesis after Gram-negative sepsis in the rat. Adult rats (225 g, n = 36) were randomized to receive isonitrogenous isocaloric total parenteral nutrition supplemented with 264 mg of N per kilogram per day as either arginine or glycine. On day 5, each group was further randomized to control or sepsis. Sepsis was induced by injection of 8 x 10(7) Escherichia coli per 100 g body weight, and then a continuous infusion of [1-14C]leucine was started. The rats were sacrificed 4 hours later. The fractional protein synthesis rates (percent per day) of histone, fibrinogen, albumin, and liver were determined. Supplemental arginine led to significantly increased histone (p less than 0.05, analysis of variance) and fibrinogen (p less than 0.01, analysis of variance) synthesis in the septic rats compared with all other groups. Histone and albumin synthesis were also significantly increased (p less than 0.05) in the arginine-supplemented control group compared with the glycine-supplemented control group. Arginine supplementation during sepsis significantly increased (p less than 0.05) albumin and liver protein synthesis compared with controls. Histones which are involved in DNA synthesis and are rich in arginine may play a role in the host response to stress and sepsis. These in vivo results appear to contradict hepatocyte-Kupffer cell coculture studies perhaps because of the hormonal and cytokine responses to nutrient substrate and acute septicemia.

Arginine supplementation improves histone and acute-phase protein synthesis during gram-negative sepsis in the rat

Mechanisms of nutrient alteration of hepatic protein synthesis during sepsis are unclear. In vitro, arginine downregulates endotoxin-stimulated hepatocyte protein synthesis but in vivo effects are unknown. This study evaluated the effects of supplemental arginine or glycine on fibrinogen (acute-phase protein), histone, albumin, and liver protein synthesis after Gram-negative sepsis in the rat. Adult rats (225 g, n=36) were randomized to receive isonitrogenous isocaloric total parenteral nutrition supplemented with 264 mg of N per kilogram per day as either arginine or glycine. On day 5, each group was further randomized to control or sepsis. Sepsis was induced by injection of 8 x 10(7) Escherichia coli per 100 g body weight, and then a continuous infusion of [1-14C] leucine was started. The rats were sacrificed 4 hours later. The fractional protein synthesis rates (percent per day) of histone, fibrinogen, albumin, and liver were determined. Supplemental arginine led to significantly increased histone (p < 0.05, analysis of variance) and fibrinogen (p < 0.01, analysis of variance) synthesis in the septic rats compared with all other groups. Histone and albumin synthesis were also significantly increased (p < 0.05) in the arginine-supplemented control group compared with the glycine-supplemented control group. Arginine supplementation during sepsis significantly increased (p < 0.05) albumin and liver protein synthesis compared with controls. Histones which are involved in DNA synthesis and are rich in arginine may play a role in the host response to stress and sepsis. These in vivo results appear to contradict hepatocyte-Kupffer cell coculture studies perhaps because of the hormonal and cytokine responses to nutrient substrate and acute septicemia.

Elemental diet alters macrophage function in mice

Administration of a chemically defined liquid elemental diet (ED) induces spontaneous bacterial translocation to mesenteric lymph nodes (MLN) in animal models. The influence of this process on host immunity is unclear. This study evaluated the effects of ED on peritoneal macrophage (PM phi) antimicrobial functions. Conventional C57/BL6 mice and endotoxin-resistant C3H/HeJ mice (n = 60) were randomized to be pair-fed either an ED or regular chow diet (RD) for 14 days. Blood, spleen, liver, and MLN were cultured for bacteria. PM phi were harvested for: percentage Candida albicans (CA) phagocytosis, percentage killing of CA, PM phi superoxide anion (O2-) production, and TNF-dependent macrophage cytotoxicity. Enteral feeding of ED in conventional C57/BL6 mice caused significant bacterial translocation to MLN but not other organs. Significant impairment of CA killing by PM phi occurred in the ED group and was associated with reduced O2- production. Tumor necrosis factor (TNF)-dependent cytotoxicity of PM phi was also decreased. In endotoxin-resistant C3H/HeJ mice, bacterial translocation was not observed and PM phi antifungal functions remained similar in both RD and ED groups. Thus, enteral feeding of an elemental diet downregulates host oxidative and antimicrobial mechanisms and TNF-dependent cytotoxicity in conventional mice which may be secondary to elemental diet-induced bacterial translocation.

Immunosuppressive mechanisms in protein-calorie malnutrition

Protein-calorie malnutrition (PCM) induces immunosuppression leading to increased mortality rates. Impaired macrophage respiratory burst activity (superoxide anion [O2-] generation) occurs in PCM, but cellular mechanisms are unclear. The major pathway resulting in O2- production involves inositol lipid-dependent signal transduction. This study examined the effect of mild versus severe PCM on macrophage O2- generating signal transduction pathways specific for responses to Candida albicans. Mice (CFW/Swiss Webster: n = 300) were randomized to either control or low protein diets for 3 or 8 weeks. Peritoneal macrophages were harvested for O2- production, mannose-fucose receptor (MFR) expression, membrane phospholipid analysis, arachidonic acid (AA) content, prostaglandin E2 (PGE2) production, and protein kinase C levels. O2- release was impaired in both mild and severe PCM. MFR expression was also decreased at these time points. Inositol lipid content was significantly lower at the 8-week time point only, although PGE2 and AA were significantly higher in the low protein diet group at 3 weeks. Protein kinase C levels were unchanged by PCM. Thus, mild PCM significantly increases macrophage-PGE2 production secondary to increased AA phospholipid content, with subsequent inhibition of O2- and MFR expression. Severe PCM inhibits macrophage (O2-) through depletion of critical membrane phospholipid components with subsequent impairment in signal transduction.

Protein-calorie malnutrition impairs host defense against Candida albicans

Protein-calorie malnutrition (PCM) impairs immune responsiveness predisposing to Candida albicans sepsis, but mechanisms are unclear. This study examined the effect of PCM on enteric-derived C. albicans intestinal translocation and the ability of in vivo interferon-gamma (IFN-gamma) to upregulate macrophage (MO) candidacidal mechanisms in PCM mice. Control (24% casein) and low protein (2.5%) diets were given for 4 weeks. Mice (n = 160) were fed C. albicans in their drinking water for 3 days and C. albicans translocation (mean colony-forming units (CFU)/g tissue +/- SEM) to the GI tract, liver, spleen, and kidney was assessed at 1 and 5 days following endotoxin challenge of 1, 5, and 10 mg/kg body wt. In a separate study (n = 100 mice), IFN-gamma (1000-10,000 U/day ip) vs saline was given for 3 days prior to harvesting peritoneal macrophages for assay of superoxide anion (O2-), percentage macrophage phagocytosis of C. albicans, and percentage killing of C. albicans. On Day 1, fungal translocation to the intestinal wall and systemic organs in the PCM group was significantly higher. On Day 5, mean CFU were significantly higher in the PCM group, indicating impaired organ clearance. Mean O2-, phagocytosis, and killing were significantly impaired in the PCM group (P less than 0.05), but IFN-gamma improved all functions. PCM significantly depressed host responses to C. albicans. IFN-gamma treatment enhanced candidacidal mechanisms, suggesting a therapeutic role in the malnourished host predisposed to C. albicans sepsis.

Nutritional support of patients with cancer of the gastrointestinal tract

Malnutrition is extremely common in patients with malignant disease. Whereas the causes are multifactorial, the predominant factor is the imbalance between nutrient intake and host nutrient requirements. Furthermore, the evidence suggests that cachexia is related to abnormal changes in host intermediary metabolism induced by host-tumor interactions, and endogenous peptides such as TNF may be important mediators. The role of nutritional therapy in cancer patients remains to be defined. Clearly, patients with severe malnutrition benefit from nutritional intervention. However, the benefit of nutritional therapy in less severe cases of malnutrition as an adjuvant to oncologic therapy has yet to be established.

Dietary manipulation of methotrexate-induced enterocolitis

Administration of chemotherapy is limited by host toxicity, which is often manifested by severe enterocolitis. This study evaluated the effects of a liquid, elemental, chemically defined diet (ED) supplemented with 2% glutamine (Glu-ED) compared with a polypeptide diet (PPD) on the morbidity and mortality after methotrexate (MTX) administration. Fischer 344 rats (n = 80) were fed either a regular rat chow diet (RD), a 2% glycine supplemented elemental diet (Gly-ED), a 2% glutamine-supplemented elemental diet (GLU-ED), and a glycine-supplemented polypeptide diet(Gly-PPD) for 7 days prior to administration of MTX (20 mg/kg, ip). After 72 hours, eight rats per group were killed; portal vein and vena cava blood, mesenteric lymph nodes (MLN), liver, small intestine, and cecum were sampled for bacterial culture. Remaining animals were followed to calculate survival. One hundred percent of the Gly-PPD and 25% of the Glu-ED animals survived compared with 0% of the Gly-ED animals. Our data showed that ED resulted in an increased quantity of intestinal Gram-negative bacteria and diminished intestinal mucosal height and mucosal DNA/protein content. The polypeptide diet prevented intestinal mucosal atrophy, avoided MTX-induced enterocolitis and significantly improved animal survival compared with an elemental diet with or without glutamine supplementation.

Impaired macrophage function in severe protein-energy malnutrition

Protein-energy malnutrition induces immunosuppression that predisposes to sepsis, but the mechanisms are unclear. This study examines the role of the macrophage in host defense in the malnourished state. Swiss-Webster mice (N = 300) were randomly allocated to control (24% casein) or low-protein (2.5% casein) diets for 8 weeks. We studied the ability of two populations of macrophages, peritoneal macrophages, and Kupffer cells to produce superoxide anion after in vivo administration of endotoxin or mycobacterium (bacille Calmette-Guérin). Phorbol diester and Candida albicans were used as stimuli. In another group of mice, we evaluated the ability of interferon gamma to up-regulate superoxide anion release and Candida phagocytosis and killing. Mice under protein-energy malnutrition demonstrated decreased mean body weights, serum protein levels, and cell yields. Superoxide anion production in resident and activated (lipopolysaccharide, interferon gamma, bacille Calmette-Guérin infection) peritoneal macrophages was significantly reduced in the malnourished group. Candida phagocytosis and killing were also both depressed in malnourished mice. Kupffer cells failed to generate superoxide anion in all groups. We conclude that severe protein-energy malnutrition significantly impairs macrophage function, which could diminish response to acute and chronic septic challenges. Interferon gamma up regulated peritoneal macrophage and Kupffer cell microbicidal function, which suggests a therapeutic role for this lymphokine in the malnourished septic host.

Comparison of acute and chronic protein-energy malnutrition on host antitumor immune mechanisms

Protein-calorie malnutrition (PCM) is prevalent in cancer patients. However, the effect of PCM on anti-tumor immunity is unclear and critically important in an era of improving results with adoptive immunotherapy. This study examined the effect of short- and long-term PCM on tumor-specific and natural immune effector mechanisms in a murine neuroblastoma (C1300 NRB) model. A/J mice received an isocaloric 2.5% or 24% casein diet for 3 or 8 weeks before inoculation with tumor. Three weeks later lymphocytes from tumor-bearing mice were harvested for determination of cytotoxic T lymphocyte (CTL) generation and natural killer (NK) cell cytotoxicity. Both 3 and 8 weeks of PCM significantly reduced mean total body weight by 25% (p less than 0.001) and 41% (p less than 0.001), respectively, compared with regularly nourished mice. Short-term PCM did not inhibit CTL or NK cytotoxicity, whereas long-term PCM significantly diminished CTL generation (p less than 0.001) but preserved NK cytotoxic function. These results indicate that CTL development against autologous tumor, in contrast to basal NK function, is dependent on host nutritional status. Mean tumor growth, determined by tumor-weight to carcass-weight ratio, was unchanged for both short- and long-term protein-energy deprived groups compared with results in regularly nourished mice. These findings suggest that NK function is the predominant effector mechanism inhibiting C1300 NRB growth and that NK tumoricidal capacity is preserved during PCM.

Surgical management of adrenal disease

This study reviews the surgical management of adrenal disease over a 23 year period in a Dublin teaching hospital. Nineteen patients were diagnosed as having either Medullary or Cortical disease. Ultrasound and CAT Scan proved highly accurate in pre-operative tumour localisation. This analysis highlights the atypical presentation of phaeochromocytoma, the accuracy of Ultrasound and CAT Scan in tumour localisation and the importance of peri-operative monitoring.

Surgical anatomy of the human spleen

Post-splenectomy sequelae are now well recognized, and conservative splenic surgery is widely advocated. However, controversies exist regarding splenic surgical anatomy. We studied 127 human spleens using anatomical dissection and a sequential injection method involving both radiology and corrosion casting, with the primary aim of examining segmental splenic anatomy and blood supply. The existence of well-defined splenic segments was confirmed and these ranged in number from 3 to 7 with a mean of 4.3. Each segment had its own arterial supply and venous drainage. The segments were separated from each other by avascular planes. Subsegments with independent blood supply were also identified. The splenic artery was found to divide into two branches; in all cases these further divided into segmental arteries supplying the central segments of the spleen. The polar segments were supplied by segmental vessels of highly variable origin and size. This study aims to highlight the importance of identifying these segmental vessels at operation when splenic conservation is considered.

Radiological assessment of atlanto-axial injuries

Injury to the cervical spine is a potentially lethal condition, and the accurate detection of such injury is essential. Plain cervical radiography remains the first line of investigation, despite well documented difficulty with interpretation. There have been many studies demonstrating unreliability of plain cervical radiography in detecting atlanto-axial injuries. We report a group of patients in which false-positive interpretation of such injuries occurred.

A non-invasive method in the assessment of surgically created arteriovenous fistulae for uraemia

Subcutaneous arteriovenous fistulae are constructed regularly for haemodialysis in uraemia. However there is little available data on fistula blood flow patterns. Twenty-eight radio-cephalic fistulae constructed for 18 patients were examined over a 3-month-period using range gated pulsed Doppler ultrasound. Contralateral arms were also examined. The parameters measured were mean arterial and venous diameter, mean volume flow and mean velocity flow. The values obtained from successful and failed fistulae were compared. There was no statistical difference between either arterial or venous diameter in the two groups. Mean velocity flow and mean volume flow in the successful group however did differ significantly from those that failed. Unless the values obtained at 48 h are significantly higher than the contralateral arm, then the fistula seems unlikely to succeed. It would also seem that a simple Doppler flow meter which gives reliable mean velocity flow values is sufficient for these investigations and may even be used preoperatively, resulting in fewer re-operations.