Immunologic abnormalities in myelofibrosis with activation of the complement system

Eighteen patients with agnogenic myeloid metaplasia with myelofibrosis were studied for clinical and laboratory evidence of immunologic dysfunction. Clinical findings included the presence of arthritis, vasculitis, and erythema nodosum. Laboratory abnormalities included the presence of circulating immune complexes, antinuclear antibodies, positive direct Coombs tests, elevated latex fixations, and a circulating lupus type anticoagulant. Total hemolytic complement was markedly depressed in four patients. Analysis of complement (C) components C1-C9 and factor B demonstrated significant reduction of only C3 and factor B. By crossed-immunoelectrophoresis, both C3 and factor B, but not C4, were cleaved, indicating that C activation was occurring predominantly via the alternative pathway. The control proteins beta 1H and C3b inactivator were decreased in three of four patients with hypocomplementemia. These data suggest that immunologic mechanisms associated with activation of the complement system play an important role in the disease process of some patients with agnogenic myeloid metaplasia with myelofibrosis.     

Ovarian haemangioma

Although ovaries have a very rich vasculature, haemangiomas of the ovary are extremely rare. There are only another 39 cases of ovarian haemangioma recorded in the literature. We describe an 11-year-old girl with an ovarian haemangioma who presented clinically with an acute abdomen. The patient has been well without complications for a year.     

Mac-1 (CD11b/CD18) and the urokinase receptor (CD87) form a functional unit on monocytic cells

The leukocyte integrin Mac-1 (CD11b/CD18) and the urokinase receptor (uPAR, CD87) mediate complementary functions in myelomonocytic cells. Both receptors promote degradation of fibrin(ogen) and also confer adhesive properties on cells because Mac-1 and uPAR bind fibrin and vitronectin, respectively. Staining of lung biopsy specimens from patients with acute lung injury indicated that fibrin and vitronectin colocalize at exudative sites in which macrophages bearing these receptors accumulate. Because of the parallel roles and physical proximity of Mac-1 and uPAR, the capacity of these receptors to functionally interact was explored. Induction of Mac-1 and uPAR expression on monocytic cell lines by transforming growth factor- beta 1 and 1.25-(OH)2 vitamin D3 conferred urokinase and uPAR-dependent adhesion to vitronectin, which was further promoted by engagement of Mac-1. Vitronectin attachment promoted subsequent Mac-1-mediated fibrinogen degradation threefold to fourfold. In contrast, enhancement of uPAR occupancy by exogenous urokinase or receptor binding fragments thereof inhibited Mac-1 function. Addition of urokinase progressively inhibited Mac-1-mediated fibrinogen binding and degradation (maximal inhibition, 91% +/- 14% and 72% +/- 15%, respectively). Saturation of uPAR with urokinase also inhibited binding of the procoagulant Mac-1 ligand, Factor X. These inhibitory effects of uPAR were reproduced in fresh monocytes, cultured monocytic cells, and in Chinese hamster ovary (CHO) cells transfected with both human Mac-1 and human uPAR. These data show that the procoagulant and fibrinolytic potential of monocytic cells is co-ordinately regulated by ligand binding to both Mac-1 and uPAR and identify uPAR as a regulator of integrin function. Vitronectin- enhanced fibrin(ogen) turnover by Mac-1 may operate as a salvage pathway in the setting of urokinase and plasmin inhibitors to promote clearance of the provisional matrix and subsequent healing.     

Effects of parenteral recombinant human macrophage colony-stimulating factor on monocyte number, phenotype, and antitumor cytotoxicity in nonhuman primates

Recombinant human macrophage colony-stimulating factor (rhM-CSF) was given to cynomolgus monkeys by continuous intravenous infusion or subcutaneous injection, at a dose of 50 to 100 micrograms/kg/d in repetitive 14-day cycles. Starting within 24 to 48 hours of initiation of rhM-CSF, there was a progressive increase in the number of circulating monocytes, from a baseline of 811 +/- 253 cells/microL to a peak of 3,495 +/- 712 cells/microL on day 5 to 7. Many of these cells were large, granular, and extensively vacuolated. The expanded cell population expressed HLA-DR, LFA3, CD11b (904), and CD14 (MY4), and was 77% CD16 (FcRIII) positive by two-color cytofluorometry. In functional assays, fresh monocytes showed little cytotoxicity against cultured human melanoma cells (SKMel-1), with or without prior rhM-CSF treatment. However, after 3 days of in vitro culture in rhM-CSF, monocytes from treated animals mediated efficient antibody-dependent cytotoxicity (ADCC) against SKMel-1 using the murine monoclonal antibody 3F8 (IgG3, anti-ganglioside GD2). Under the same conditions, monocytes from control animals showed little ADCC (17% versus 82%, P less than .05). Antitumor cytotoxicity in the absence of antibody was less efficient and was not significantly different between the two groups. There was a mild decrease in platelet count during rhM-CSF treatment, without clinical symptoms. No abnormalities of serum biochemical parameters were seen. We conclude that parenteral rhM-CSF increases the number of circulating monocytes in nonhuman primates, and that these monocytes mediate increased antitumor ADCC after a brief period of in vitro differentiation. This study has implications for the design of possible future clinical trials combining antitumor monoclonal antibodies and rhM-CSF.     

Summer-type relapsing fever (hypersensitivity pneumonitis) secondary to Cladosporium herbarum in the domestic environment

‘Summer-type relapsing fever’ is the most prevalent form of hypersensitivity pneumonitis in Japan. It is usually caused by hypersensitivity to Trichosporon cutaneum – a seasonal mould which thrives in homes with damp, decayed wood, damp mats and bedclothes. The disease has been rarely described outside Japan. We report the first documented case of summer-type hypersensitivity pneumonitis in Europe – in this case caused by hypersensitivity to the mould Cladosporium herbarum.     

Inhibition of lysosomal enzyme activities by proton pump inhibitors

Background

Proton pump inhibitors (PPIs) are pro-drugs requiring an acidic pH for activation. The specificity of PPI toward the proton pump is mainly due to the extremely low pH at the parietal cell canalicular membrane where the pump is located. Reactivity of PPIs was also observed in moderately acidic environments like the renal collecting duct. But no PPI effect on lysosomal enzymes has been observed possibly because the previous studies were performed with liver tissue, where PPIs are metabolized.

Methods

The reactivity of PPIs (omeprazole, lansoprazole and pantoprazole) with a cysteine-containing peptide was analyzed by mass spectrometry, and the impact of PPIs on lysosomal enzymes was evaluated in cultured cells and mice. The effect of PPIs on the immune system was examined with a mouse tumor immunotherapy model.

Results

Incubation of a cysteine-containing peptide with PPIs at pH5 led to the conversion of most of the peptide into PPI-peptide adducts. Dose dependent inhibition of lysosomal enzyme activities by PPIs was observed in cultured cells and mouse spleen. Further, PPI counteracted the tumor immunotherapy in a mouse model.

Conclusions

Our data support the hypothesis that many of the PPI adverse effects are caused by systematically compromised immunity, a result of PPI inhibition of the lysosomal enzymes. This novel mechanism complements the existing mechanisms in explaining the increased incidence of tumorigenesis and infectious diseases among PPI users and underlie the ongoing concern about the overuse of PPIs in adult and pediatric populations.