Global vascular expression of murine CD34, a sialomucin-like endothelial ligand for L-selectin

Extravasation of leukocytes into organized lymphoid tissues and into sites of inflammation is critical to immune surveillance. Leukocyte migration to peripheral lymph nodes (PLN), mesenteric lymph nodes (MLN) and Peyer's patches (PP) depends on L-selectin, which recognizes carbohydrate-bearing, sialomucin-like endothelial cell surface glycoproteins. Two of these ligands have been identified at the molecular level. One is the potentially soluble mucin, GlyCAM 1, which is almost exclusively produced by high endothelial venules (HEV) of PLN and MLN. The second HEV ligand for L-selectin is the membrane-bound sialomucin CD34. Historically, this molecule has been successfully used to purify human pluripotent bone marrow stem cells, and limited data suggest that human CD34 is present on the vascular endothelium of several organs. Here we describe a comprehensive analysis of the vascular expression of CD34 in murine tissues using a highly specific antimurine CD34 polyclonal antibody. CD34 was detected on vessels in all organs examined and was expressed during pancreatic and skin inflammatory episodes. A subset of HEV-like vessels in the inflamed pancreas of nonobese diabetic (NOD) mice are positive for both CD34 and GlyCAM 1, and bind to an L-selectin/immunoglobulin G (IgG) chimeric probe. Finally, we found that CD34 is present on vessels of deafferentiated PLN, despite the fact that these vessels are no longer able to interact with L-selectin or support lymphocyte binding in vitro or trafficking in vivo. Our data suggest that the regulation of posttranslational carbohydrate modifications of CD34 is critical in determining its capability to act as an L-selectin ligand. Based on its ubiquitous expression, we propose that an appropriately glycosylated form of vascular CD34 may act as a ligand for L-selectin-mediated leukocyte trafficking to both lymphoid and nonlymphoid sites.     

Splenic involvement in infectious endocarditis. 5 clinical cases and 78 necropsies

Splenic involvement is a classical complication of infective endocarditis (IE). Clinical manifestations are rare, 5 out of 100 IE: unexpected rupture (1 case), abscess causing reinfection (2 cases), pseudo-tumour (1 case) and terminal infarction (1 case). In addition to a review of the literature, a post mortem histological study of the spleen of 78 cases of IE was undertaken. Splenic involvement did not seem to be the direct cause of death. Three types of lesions which may or may not be associated were observed: congestive inflammatory lesions, infarction (48 p. 100), abscess (6 p. 100). Splenic infarction usually results in scarring but may progress to abscess formation. Rupture was not observed in this autopsy series. Although splenic involvement is common at post mortem it gives rise to few symptoms. Persistant pyrexia and the appearance of local signs should lead to investigation of splenic complications and eventually, to surgical ablation.     

Importance of planning ovulation induction therapy in systemic lupus erythematosus and antiphospholipid syndrome: a single center retrospective study of 21 cases and 114 cycles

OBJECTIVE: To analyze the results and complications of ovulation induction therapy (OIT) in women with systemic lupus erythematosus (SLE) and/or the antiphospholipid syndrome (APS). METHODS: A retrospective study of 21 women followed in a single tertiary-referral French center who underwent 114 OIT cycles with or without in vitro fertilization and embryo transfer (IVFET). RESULTS: Before OIT, SLE was present in 6 women, APS in 3, SLE-related APS in 3, and discoid lupus in 1. Eight women had no identified disease and underwent 36 cycles of OIT. Diagnosis (SLE, n = 3; primary APS, n = 5) was made after OIT complication: spontaneous abortion (n = 5), SLE flare (n = 2), and thrombophlebitis (n = 1). Five women with known disease intentionally concealed their history from their gynecologists and underwent 34 cycles. Forty-four cycles were planned in 11 women, in 3 of them after complications of prior OIT performed without particular therapy and monitoring. Eighteen pregnancies occurred, which ended in 9 live births, 4 fetal deaths, and 5 embryonic losses. The pregnancy rate was higher with gonadotropin and/or gonadotropin-releasing hormone analog (GnRHa) (25% of cycles) than with clomiphene (4% of cycles, P <.0001). When the gynecologists did not know the underlying disease, three-quarters of pregnancies induced by OIT with IVFET ended in embryonic losses or fetal deaths. In contrast, 6 of 7 pregnancies induced by planned OIT with IVFET ended in live births (P <.0001). Phlebothromboses were observed only with gonadotropin treatment. The SLE flare rate was higher with gonadotropin and/or GnRHa (27% of cycle) than with clomiphene (6%, NS). It also was higher (30%) when the gynecologists did not know the underlying disease than in the planned procedures (10%, NS). CONCLUSIONS: The OIT may precipitate SLE or APS. A careful review of the patient's history and appropriate laboratory tests should be undertaken before OIT. Clomiphene complications are rare. When gonadotropins are prescribed, preventive anti-inflammatory therapy should be considered in women with SLE, in addition to heparin and/or anti-aggregant therapy in patients with asymptomatic anti-phospholipid antibodies or prior thrombotic events.     

Red blood cell regeneration induced by subcutaneous recombinant erythropoietin: iron-deficient erythropoiesis in iron-replete subjects [see comments]

Limited red blood cell (RBC) regeneration often prevents collection of sufficient blood from autologous donors. We studied the effects of subcutaneous recombinant erythropoietin (rEPO) in subjects making frequent blood donations. Six healthy iron-replete male subjects took rEPO (200 U/kg) subcutaneously daily, and donated blood (450 mL) twice a week for 3 weeks. During a control study, these subjects also attempted twice-weekly blood donations without rEPO. Four other males given rEPO, including one with idiopathic hemochromatosis, waited until day 8 to begin blood donations. All healthy subjects took oral ferrous sulfate. Subcutaneous rEPO given with blood donations resulted in a marked reticulocytosis (mean peak value 568 +/- 159 x 10(9)/L v 235 +/- 77 x 10(9)/L, control study; P < .05), and enhanced RBC production at 28 days (1,208 +/- 227 mL v 719 +/- 161 mL, P < .05). rEPO in advance of blood donations was slightly less effective in normal subjects (941 +/- 139 mL, P < .05); however, the subject with hemochromatosis produced substantially more RBCs (1,764 mL) than any normal subject. rEPO-treated normal subjects (but not the rEPO-treated patient with hemochromatosis or untreated controls) produced iron-deficient RBCs with elevated zinc protoporphyrin levels and low hemoglobin content. These cells appeared within 1 week of rEPO administration and before laboratory confirmation of depleted iron stores. Thus, subcutaneous rEPO is an effective stimulant of erythropoiesis in nonanemic blood donors. However, in addition to eventual depletion of iron stores, early functional iron deficiency affects response to the drug.     

Beta 2-integrin and L-selectin are obligatory receptors in neutrophil aggregation [see comments]

We have recently found that antibodies to L-selectin, the homing receptor on neutrophils, are as effective as those to beta 2-integrin at blocking formyl peptide-stimulated aggregation. Therefore, we investigated the requirements for expression of L-selectin and beta 2- integrin on adjacent cells during aggregation. Fluorescence flow cytometry allowed characterization of aggregates on the basis of size and color, as well as antibody binding to these two adhesive molecules. Formyl peptide-stimulated aggregate formation was measured for individual populations fluorescently labeled red (LDS-751) or green (CD44-FITC), and interpopulation red-green cell conjugates. Blocking either the beta 2-integrin or L-selectin adhesive epitope with monoclonal antibody on individual cell populations resulted in an approximately 50% reduction in two-color aggregation as compared with that in unblocked samples. Shedding the L-selectin on a cell population by preincubation with complexes of lipopolysaccharide and its plasma membrane binding protein also decreased aggregation to a control population by approximately 50%. We examined the aggregation of neutrophils from patients genetically deficient in beta 2-integrin and clinically leukocyte adhesion deficient (LAD). LAD adhesion to normal neutrophils was dependent on the expression of L-selectin on LAD cells and beta 2-integrin on normal cells. Thus, the minimum requirement for adhesion between two mixed populations of neutrophils was that one population expressed the beta 2-integrin and the other expressed the L- selectin adhesive epitope.     

Expression of specific granule markers on the cell surface of neutrophil cytoplasts

The widespread assumption that cytoplasts generated from human polymorphonuclear leukocytes (PMNs) are vesicles consisting solely of cytoplasm surrounded by plasma membrane and devoid of granule activity remains to be tested. PMN cytoplasts were prepared by centrifugation of intact cells on a Ficoll step gradient in the presence of cytochalasin B. Two granule membrane markers, Mol, a fluorometrically detectable antigen, and cytochrome b, both of which have been shown to translocate to the plasma membrane during granule release, were compared for their activity in cytoplasts and intact PMNs. We found that the amount of Mol detected on the plasma membrane of intact PMNs, as compared with other membrane markers (such as antigens LFA-1 and beta 2m), increased 1.6- fold upon exposure of PMNs to Ficoll plus cytochalasin B prior to centrifugation. Another twofold increase in Mol expression occurred upon cytoplast preparation. Release of the granule enzymes, vitamin B12- binding protein, and lysozyme were also followed and correlated well (r = .78 and .92) with the amount of Mol antigen present on the cell surface. Cytochrome b was also found to be higher (1.4-fold) on plasma membranes isolated from cytoplasts than on plasma membranes isolated from intact control cells. These results indicate that some fusion of granule membranes and plasma membranes occurred during treatment of PMNs with Ficoll plus cytochalasin b and during cytoplast preparation.