Mixed erythrocyte chimerism: implications for tolerance of the donor immune system to recipient non-ABO system red cell antigens.

We report a case of a minor degree of ABO incompatibility in a BMT recipient, demonstrating mixed RBC chimerism, who, late in the post-transplant period, developed a warm autoimmune hemolytic anemia and subsequently developed antibodies with donor-anti-recipient specificities for non-ABO system RBC antigens. While this implies a lack of tolerance of the donor immune system for recipient non-ABO system RBC antigens, other factors may be operating and should be evaluated before such a conclusion is reached. Underscored is the importance of obtaining pretransplant RBC antigen phenotypes on both the recipient and donor.

Gamma-interferon inhibits Fc receptor II-mediated phagocytosis of tumor cells by human macrophages.

In vitro, monocyte-derived macrophages (MDM) are capable of efficient antibody-mediated phagocytosis of human nucleated tumor cells. These MDM express on their cell surface all three classes of Fc receptors for IgG (Fc gamma R). Fc gamma R specificity for murine antibody isotype allowed us to examine the phagocytic role of Fc gamma RII on control and gamma-interferon (IFN-gamma)-primed MDM. Monoclonal antibody 520C9 (IgG1) mediates phagocytosis through Fc gamma RII. This monoclonal antibody is directed against the HER-2/neu protooncogene product overexpressed on a variety of adenocarcinomas including the breast carcinoma cell line SK-BR-3. Our results showed that IFN-gamma treatment of differentiated MDM (days 8-12 in culture) inhibited Fc gamma RII-mediated phagocytosis in a dose-dependent manner with negative effects noted at doses as low as 0.1 units/ml. The percentage reduction in antibody-mediated phagocytosis observed following IFN-gamma priming (40 units/ml for 18 h) ranged from 23-89% of control. The inhibitory effect was evident when exposure to IFN-gamma was transient. Fc gamma RII expression was not altered by IFN-gamma treatment. In our model, IFN-gamma did not up-regulate or down-regulate HER-2/neu protein expression on our targets or affect the level of CD14 antigen expression on our MDM. Although IFN-gamma is a potent activator of monocytes/macrophages and can enhance certain tumoricidal mechanisms, our data show that antibody-dependent phagocytosis through the type II Fc receptor is inhibited by IFN-gamma priming. Nonspecific phagocytosis was not affected.

Effect of cortical-medullary gradient for ammonia on urinary excretion of ammonia.

Previous studies suggested that a portion of ammonia secreted into the proximal tubule may diffuse directly from Henle's loop into the medullary collecting duct. Since water is absorbed along the course of the descending portion of the loop, it was proposed that the concentration of ammonia increased in loop fluid, and that rapid diffusibility of the free base would facilitate the delivery of ammonia into medullary interstitium where a high level could be maintained by the countercurrent exchange process. In this schema it was proposed that there was an ammonia concentration gradient between medullary structures and cortex, and recovery of ammonia by the medullary collecting duct due to the low pH in tubule fluid at that site. The present study was designed to evaluate this hypothesis by estimating ammonia concentrations in medullary and cortical tissue, and by correlating medullary levels with secretion rate into the inner medullary collecting duct. In control animals the concentration of total ammonia (NH4+ + NH3+) in inner medullary vasa recta was 9.2 +/- 1.5 mumoles/ml, a level 100-fold higher than the cortical level of 0.10 +/- 0.01. During acute acidosis the medullary level rose to 22.5 +/- 2.7 mumoles/ml, but in acute acidosis during mannitol infusion the level fell to 8.0 +/- 1.2. The rate of ammonia secretion into inner medullary collecting duct fluid correlated directly with medullary vasa recta ammonia concentration. These data provide evidence for a steep ammonia concentration gradient between the medulla and cortex, and suggest that the diffusion gradient across collecting duct epithelium governs the rate of the addition of ammonia to collecting duct fluid.

Role of the medullary collecting duct in potassium conservation.

A capacity for both net potassium absorption and net potassium secretion has been demonstrated in the inner medullary collecting duct. The quantitative importance, however, of the inner medullary collecting duct in the regulation of urinary potassium in potassium deficiency, however has not been established. To assess the contribution of this segment to potassium conservation, microcatherization studies were performed in male Sprague-Dawley rats maintained either on a control diet or on a potassium free diet for 72 h. In control animals approximately 15% of the filtered load of potassium was excreted. Analysis of tubule fluid along the inner medullary collecting duct failed to demonstrate evidence of net potassium movement. Administration of a potassium free diet resulted in a marked reduction in potassium excretion to 0.3% of the filtered load. In contrast to control the inner medullary collecting duct of experimental animals absorbed nearly 90% of the amount of potassium entering this segment, since fractional delivery to the terminal portion of the nephron was about 2%. These data indicate that the inner medullary collecting duct makes a significant contribution to maximal renal conservation of potassium, since previous studies have shown that only 5 to 10% of filtered potassium is present in the late distal tubule of surface nephrons in animals on a low potassium intake.

Concealed haematuria--whence cometh the bleeding? A new method of localisation.

Concealed haematuria is often a difficult diagnostic problem. A method for collecting isolated urine specimens from different areas of the urinary tract and subjecting them to quantitative analysis for RBCs is described. A more accurate localisation of the source of bleeding with, in the upper urinary tract, side differentiation, is thus possible. Some examples are presented as case reports.

Erythrocyte limits in haematuria.

The boundary-line between gross haematuria and microscopical haematuria is estimated to be at 5000 erythrocytes/mm3 of urine. The quantification is made by counting red blood cells in freshly voided non-centrifuged urine. A naked eye estimation of the colour of each tube was performed with a light beam from both in front (Fig. 1) and behind (Fig. 2). The colour observed can be correlated to the quantity of RBC/mm3.

Role of the medullary collecting duct in potassium excretion in potassium-adapted animals.

Previous studies have demonstrated that the rate of urinary potassium excretion is markedly greater in animals fed a high potassium diet than in animals on a control diet before and during the acute infusion of potassium salts. Because the contribution of the medullary collecting duct to urinary potassium under these conditions has not been determined, microcatheterization studies were performed to elucidate the role of that nephron segment in regulating potassium excretion in controls and in animals on a potassium-enriched diet. Although there was no evidence of net transport of potassium by the medullary collecting duct in control animals under basal conditions, net secretion of potassium by that nephron segment accounted for nearly one half of the increased rate of urinary excretion in animals fed a high potassium diet. During acute infusion of potassium salts, potassium secretion by the medullary portion of the collecting duct contributed approximately one half of the potassium in the final urine samples in both controls and animals fed a high potassium diet. Because the rate of urinary excretion was twofold greater in experimental animals during acute potassium loading, absolute potassium secretion in medullary collecting duct was twice the control rate in animals adapted to a high potassium dietary intake. These data demonstrate, therefore, that the medullary collecting duct plays an important role in regulating the excretion of potassium when the excretory load is either acutely or chronically increased.

Pheochromocytoma of the bladder. A case report.

A 39-year-old male patient with attacks of headache and tachycardia immediately after micturition is described. Systolic blood pressure of 250 mmHg was measured after voiding. Plasma noradrenaline was increased 10 to 20 times above the normal value during the attacks. Cystoscopy, arteriography, catheterization of the caval vein with sampling for plasma catecholamines and computerized tomography all supported the diagnosis of a bladder tumour. A beneficial effect of alpha-receptor blockade preoperatively was demonstrated. The tumour was operatively removed from the bladder. The postoperative course was uneventful.

Electrical properties of the medullary collecting duct in the rat.

Studies were performed in the rat to determine the transepithelial potential difference (PD) of the medullary collecting duct (MCD). With the microcatheter as an exploring electrode the PD from duct lumen to the reference electrode, placed in peritoneal fluid, was approximatley 1 mV, lumen positive, in the MCD. It was unlikely that the polarity and small magnitude of PD was due to an artifact created by the microcatheter, since essentially similar results were obtained by transmural puncture of the inner third of the duct using Ling-Gerard glass electrodes and glass microelectrodes, tip OD 3-5 micron. Moreover, a PD of a few millivolts, lumen positive, was observed in experimental states characterized by marked increases in potassium and hydrogen ion secretion and sodium absorption. Further studies showed that the diffusion potential existing within the interstitial fluid compartment, between papilla and reference electrode, was approximately +2 mV, owing to the higher NaCl concentration in the papillary area. These data demonstrate, therefore, that the transepithelial PD in MCD approaches zero in control animals, and is not substantially altered by marked changes in net electrolyte transport.