Mouse macrophage development in the absence of the common γ chain: defining receptor complexes responsible for IL-4 and IL-13 signaling

The common γ chain (γ_c) forms a critical component of the receptors for interleukins (IL)-2, IL-4, IL-7, IL-9, and IL-15. We analyzed γ_c-deficient mice to define a role for γ_c signaling in the development and function of the macrophage lineage. No major differences in absolute cell numbers, cell surface phenotype, or in vitro function of γ^?_c compared to γ⁺_c macrophages were observed. We therefore conclude that signaling through the γ_c chain is not essential for the differentiation of mouse macrophages. Although B and T cells require γ_c for IL-4 responses, IL-4 up-regulated major histocompatibility class II molecules and inhibited nitric oxide production from γ^?_c macrophages following stimulation with lipopolysaccharide and interferon-γ. γ^?_c macrophages could also respond to IL-13, consistent with the model of a type II IL-4 receptor α/IL-13R which can function in the absence of γ_c. Both IL-4 and IL-13 responses could be completely inhibited with the mouse IL-4 antagonist QY, suggesting that all of the observed IL-13 responses pass through the type II receptor, making it the primary signaling receptor complex for IL-13 in mouse macrophages.     

Activation and internalization of p56lck upon CD45 triggering of Jurkat cells

Relationships between CD45 and p56^Ick have been suggested by co-immunoprecipitation of both proteins and by dephosphorylation of the p56^lck regulatory site, Tyr 505, by CD45 in vitro. We investigated whether the kinase activity of p56^lck is modulated in T cells triggered via CD45. We showed that incubation of Jurkat cells with a combination of two anti-CD45 monoclonal antibodies (mAb) (MC5/2 + D3/9) induced an increase in p56^lck kinase activity, while a single mAb did not. Under these conditions, p56^lck underwent two consecutive waves of activation. This was accompanied by internalization of the kinase and by a time-dependent increased accessibility of CD45 phosphatase at the plasma membrane. Similarly, activation and internalization of p56^lck were observed using a combination of anti-CD45 (MC5/2) and anti-CD2(T11₂) mAb, suggesting that a functional complex consisting of CD45, CD2 and p56^lck was formed upon cell triggering. Taken together, these results suggests that: (i) CD45 participates in the regulation of p56^lck kinase activity in vivo and that (ii) CD45 could play a mediator role in the stimulation and endocytosis of p56^lck through the CD2 pathway.     

Release of acetylcholine in the ventral striatum is influenced by histamine receptors

To investigate whether histamine receptor ligands influence thein vivo-release of acetylcholine in the ventral striatum, this brain region was superfused with histamine receptor agonists or antagonists through a push-pull cannula and drug effects on the release of acetylcholine were investigated.

Histamine, the H₁ receptor agonist 2-thiazolyl-ethylamine and the H₃ receptor antagonist thioperamide enhanced acetylcholine release, while the H₃ receptor agonist (R)-α-methylhistamine was ineffective. The results indicate that H₁ receptors and H₃ receptors modulate acetylcholine release.

The thioperamide-induced increase of acetylcholine release might be exerted via H₃-receptors located on cholinergic terminals. Alternatively, thioperamide might enhance acetylcholine release by incresing endogenous histamine release via H₃ autoreceptors.

It is concluded that, via stimulation of striatal H₁- and H₃ receptors, histaminergic neurons are involved in the regulation of cholinergic neuronal activity in the ventral striatum.

     

Calcitonin gene products and the kidney

Summary Calcitonin gene-related peptide (CGRP) is localized in capsaicin-sensitive nerve fibres in the kidney and urogenital tract whereas calcitonin reaches the kidney through the general circulation. Systemic infusion of CGRP and perfusion of isolated rat kidney reduces vascular resistance, and increases renal blood flow and glomerular filtration. CGRP stimulates renin secretion in vivo and in vitro and inhibits contraction of isolated rat mesangial cells by angiotensin II. Calcitonin does not affect vascular resistance, renal blood flow and glomerular filtration, and is less potent in stimulating renin secretion, and does not alter contraction of isolated rat mesangial cells by angiotensin II. CGRP also exerts renal tubular effects brought about probably through interaction with calcitonin receptors. To this end, increased excretion of sodium and chloride, and stimulation of urinary flow are less pronounced with CGRP than with calcitonin. Calcitonin, moreover, stimulates the fractional urinary excretion of calcium and phosphate.     

Molecular orientation of ultrahigh molecular weight polyethylene induced by various sliding motions

Wear and wear debris of ultrahigh molecular weight polyethylene (UHMWPE) in joint replacements have been recognized as one of the major contributors to the failure of orthopedic implants. The detailed wear mechanism of polyethylene under biomechanic motions is not well understood. In simulation wear bench tests, it was found that unidirectional sliding produces the least amount of wear, reciprocating motion increases wear significantly, and cross-shear motion (similar to hip and knee joint motion in the human body) produces the highest amount of wear. Conventional wear theories are inadequate to explain this observation. This study utilizes resonant absorption of linearly polarized soft X-rays at a synchrotron radiation beam line to measure the molecular orientation of a UHMWPE surface layer subjected to different wear motions. Carbon-K-edge partial-electron-yield X-ray absorption measurements were done on the worn UHMWPE samples. X-ray absorption measurements show conclusively that the molecular chains of UHMWPE align preferentially parallel to the direction of sliding. Examination under various wear motions showed that unidirectional shear produced the maximum chain orientation, whereas cross-shear wear motions produced the least amount of orientation. When polymeric chains align, the surface layer tends to be more brittle and hard, thus resisting wear. When they do not align, loose chains may be subjected to both Mode I and Mode II fracture, hence increasing the wear rate. This molecular alignment observation may offer an explanation of why different wear motions have different wear characteristics.     

Helicobacter pylori gastritis and primary gastric non-Hodgkin's lymphomas.

AIMS--To evaluate further the relation between gastric malignant lymphoma of the mucosa associated lymphoid tissue (MALT) and Helicobacter pylori. METHODS--One hundred and sixty two surgical specimens of MALT lymphoma were retrospectively investigated to determine tumour type and inflammatory patterns. In 121 cases biopsy specimens obtained before surgery were available and stained with haematoxylin and eosin, periodic acid Schiff, Giemsa and Warthin-Starry stains. RESULTS--Residual lymphoid follicles were found less often in high grade malignant than in low grade malignant MALT lymphomas. Chronic active gastritis was shown within the mucosa at some distance from the tumours in 143 of 146 specimens. In all the cases for which biopsy specimens could be evaluated, colonisation of the mucosa by H pylori had occurred. Lymphoid follicles and lymphoid aggregates were detected in 82.7% of the antral, and in 85% of the body mucosa specimens. CONCLUSIONS--These data support the hypothesis that H pylori has an important role in the development of MALT lymphomas. Furthermore, the chronic inflammation preceding malignant transformation might enhance the probability of malignant transformation via chronic stimulation of the lymphoid tissue. This might in part indicate why MALT lymphomas occur most often in the stomach.     

Pathogenesis and diagnosis of human meningococcal disease using immunohistochemical and PCR assays

Neisseria meningitidis remains the leading cause of fatal sepsis. Cultures may not be available in fulminant fatal cases. An immunohistochemical assay for N meningitidis was applied to formalin-fixed samples from 14 patients with meningococcal disease. Histopathologic findings in 12 fatal cases included interstitial pneumonitis, hemorrhagic adrenal glands, myocarditis, meningitis, and thrombi in the glomeruli and choroid plexus. Meningeal inflammation was observed in 6 patients. Skin biopsies of 2 surviving patients showed leukocytoclastic vasculitis and cellulitis. By using immunohistochemical analysis, meningococci and granular meningococcal antigens were observed inside monocytes, neutrophils, and endothelial cells or extracellularly. By using real-time polymerase chain reaction (PCR) on formalin-fixed tissue samples, meningococcal serogroup determination was possible in 11 of 14 cases (8 serogroup C, 2 Y, and 1 B). Diagnosis and serogrouping of N meningitidis can be performed using immunohistochemical analysis and PCR on formalin-fixed tissue samples. Immunohistochemical analysis determined the distribution of meningococci and meningococcal antigens in tissue samples, allowing better insights into N meningitidis pathogenesis.