Rosa M. Ten

Acute Interstitial Nephritis: Immunologic and Clinical Aspects

Acute interstitial nephritis is a common renal syndrome that may be associated with a variety of infections and drug therapies or may develop without an identified cause. Three cases are presented to illustrate the three types of acute interstitial nephritis--drug related, infection related, and idiopathic. Cell-mediated immune mechanisms seem to be more important than humorally mediated mechanisms in the pathogenesis of acute interstitial nephritis. Frequently, eosinophils are identified as a component of the interstitial cellular infiltrate, and eosinophiluria and eosinophilia have been claimed to be helpful in the diagnosis of acute interstitial nephritis, especially the drug-induced type. Neither eosinophiluria nor the presence of increased urinary levels of eosinophil major basic protein, however, is specific for the diagnosis of acute interstitial nephritis. Patients with drug-induced interstitial nephritis frequently have symptoms and signs suggestive of a hypersensitivity syndrome and rarely have more dramatic anaphylactic manifestations. Systemic glucocorticoids have been shown to be beneficial in this type of acute interstitial nephritis.

The Anti‐Androgen Hydroxyflutamide and Androgens Inhibit Interleukin‐6 Production by an Androgen‐Responsive Human Osteoblastic Cell Line

While androgens clearly have significant skeletal effects, the paracrine mediators of androgen action on bone are at present unclear. Interleukin‐6 (IL‐6) is a candidate cytokine that is produced by osteoblastic lineage cells and promotes osteoclastogenesis and bone resorption. Here, we assessed constitutive as well as IL‐1β– and tumor necrosis factor‐α (TNF‐α)–stimulated IL‐6 mRNA expression by Northern analysis and protein secretion by immunoassay in a human androgen‐responsive osteoblastic cell line (hFOB/AR‐6) which contains ∼4000 androgen receptors (ARs)/nucleus. Treatment with 5α‐dihydrotestosterone (DHT) dose‐dependently inhibited constitutive and TNF‐α/IL‐1β–stimulated IL‐6 mRNA steady‐state levels in hFOB/AR‐6 cells by 70–80% at 10−7 M. In addition, testosterone also suppressed TNF‐α/IL‐1β–stimulated IL‐6 mRNA levels by 57%, while the adrenal androgen dehydroepiandrosterone had no effect. Of note, the specific AR antagonist, hydroxyflutamide, also inhibited IL‐6 mRNA levels by 70%. Consistent with the Northern analyses, treatment with 5α‐DHT, testosterone, and hydroxyflutamide also inhibited IL‐6 protein production by 79%, 62%, and 71%, respectively (p < 0.001), while these agents had no effect on IL‐6 soluble receptor levels. Finally, we demonstrated that hydroxyflutamide treatment of hFOB/AR‐6 cells markedly inhibited the activation and binding of NF‐κB (a known stimulator of IL‐6 gene transcription) to its response element, thus providing a potential mechanism for its effect on IL‐6 production by osteoblasts. These data are consistent with the hypothesis that suppression of osteoblast IL‐6 production by androgens may mediate, at least in part, the antiresorptive effects of androgens on bone. Moreover, our findings also indicate that hydroxyflutamide, which is a known AR antagonist in most tissues, may function as a selective AR modulator for effects on IL‐6 production by osteoblasts.

Mannose-binding lectin (MBL) deficiency. Variant alleles in a midwestern population of the United States.

OBJECTIVES To describe a method for the genotype analysis of mutations in the gene encoding mannose binding lectin (MBL), study the incidence of MBL gene mutations in a population of the Midwest of the United States, and compare it with previous reports in other populations. The objective of this report is also an extensive review of the literature to analyze the importance of MBL deficiency in human disease. DATA SOURCES Blood samples were obtained from the blood bank of the Mayo Clinic. They represented a population of blood donors living in the Midwest of the United States. A review of the literature was performed by selection of articles from Medline database. STUDY SELECTION Blood samples, 148, were randomly selected from a pool of blood donors. They included both females and males. Blood donors had been previously screened by a questionnaire and were found to be generally healthy. For the literature review, articles containing original data on MBL in humans were selected. RESULTS Forty-five (30.4%) of the analyzed blood donors carried one variant allele, while 8 donors (5.4%) showed homozygosity or compound heterozygosity for MBL gene mutations. Allele frequency for the different MBL variants is provided. Our results are similar to those reported for the Danish population. Literature review provides evidence for a significant role of MBL deficiency in the innate immunity. The incidence of MBL mutations is higher among patients with recurrent infections and autoimmune disorders. CONCLUSIONS Mannose binding lectin deficiency has a definite role in the pathogenesis of primary immunodeficiency in humans and screening patients with recurrent infections and autoimmunity might be beneficial. The significance of MBL deficiency among apparently healthy blood donors remains to be determined.

Eosinophil granule major basic protein in acute renal allograft rejection

Conventional staining techniques to determine the presence of tissue eosinophils underestimate their number and do not usually detect eosinophil degranulation. We have studied the involvement of eosinophils in acute renal allograft rejection by immunofluorescence localization of eosinophil granule major basic protein (MBP) in the kidney and by measurement of MBP in the plasma and urine by radioimmunoassay. Tissue eosinophilia and extracellular deposition of MBP indicative of eosinophil degranulation were observed in 94% and 87%, respectively, of patients with acute rejection as compared with 17% and 17%, respectively, of patients with cyclosporine nephrotoxicity. The urine levels of MBP were significantly elevated in acute rejection but not in cyclosporine nephrotoxicity. Plasma MBP concentrations were within the normal range in both acute rejection and cyclosporine nephrotoxicity. The presence of marked tissue eosinophilia and eosinophil degranulation did not always indicate irreversible rejection. Interleukin-2 and IL-2 receptors were also elevated in the urine during acute rejection. These results support a role for the eosinophil as an effector of tissue damage during rejection and suggest the potential usefulness of urine MBP determinations for the immunologic monitoring of transplanted patients.

Signal transduction pathways triggered by the FcϵRIIb receptor (CD23) in human monocytes lead to nuclear factor-κB activation

Abstract Background: Alveolar macrophages play a key role in the initiation of the inflammatory reaction of allergic asthma. Alveolar macrophages and peripheral blood monocytes are activated when IgE/allergen immune complexes bind to the CD23 receptor, which leads to the production of inflammatory cytokines. Objective: We sought to investigate the molecular mechanisms regulating this early inflammatory response. We have focused on the study of the signal transduction pathways triggered by CD23 in human monocytes and the promonocytic cell line U937. Methods: CD23 was cross-linked in human monocytes and U937 cells with IgE immune complexes. Surface expression of CD23 was determined by FACS analysis. Transcription factor activation and gene transcription were studied by gel-shift assays and Northern blot analysis, respectively. IκBα phosphorylation and degradation was analyzed by Western blot. Results: Nuclear factor (NF)-κB is the main transcription factor involved in the gene activation that follows CD23 cross-linking in monocytes. CD23-induced NF-κB is a heterodimer composed of p65/p50 subunits. NF-κB nuclear translocation is secondary to the phosphorylation and subsequent degradation of the NF-κB inhibitory molecule IκBα. Tyrosine kinase–dependent, and not protein kinase C–dependent, pathways mediate CD23-triggered NF-κB activation but do not participate in the direct phosphorylation of IκBα. IκBα degradation and NF-κB nuclear translocation correlate with transcriptional activation of the inflammatory cytokines TNF-α and IL-1β. Conclusions: NF-κB is the main transcription factor involved in the signal transduction pathway of CD23 in monocytes. (J Allergy Clin Immunol 1999;104:376-87.)

Eosinophil differentiation of human umbilical cord mononuclear cells and prolonged survival of mature eosinophils by murine EL-4 thymoma cell conditioned medium

Umbilical cord mononuclear cells, HL-60 cells, HL-60 clones selected for eosinophil differentiation, and the eosinophil leukemia cell line EoL were tested for their ability to produce eosinophil peroxidase. HL-60 clones selected for eosinophil differentiation produced eosinophil peroxidase, as judged by staining of cells for cyanide-resistant peroxidase activity; however, these cells lost their ability to produce eosinophil peroxidase in long-term culture. In contrast, eosinophil precursors from human umbilical cord blood mononuclear cells stimulated with murine EL-4 conditioned medium (EL-4 CM) were regularly induced to eosinophil protein synthesis, including eosinophil peroxidase, major basic protein, eosinophil cationic protein, and eosinophil-derived neurotoxin, as assessed by cyanide-resistant peroxidase and immunofluorescence staining. This induction by EL-4 CM is either at the level of gene transcription or mRNA stabilization, as shown by the increase of total mRNA for eosinophil peroxidase, major basic protein, and eosinophil-derived neurotoxin by Northern blot analyses. Purified peripheral blood eosinophils incubated for 4 days with EL-4 CM had increased survival over control eosinophils. Moreover, this enhanced survival was specifically blocked by antiserum to interleukin 5. Our results suggest that the effects of EL-4 CM on human umbilical cord mononuclear cells and mature eosinophils are due to the presence of interleukin 5.

Mannose-binding lectin deficiency associated with neutrophil chemotactic unresponsiveness to C5a

BACKGROUND Mannose-binding lectin (MBL) plays an important role in host defense by activating the complement cascade. OBJECTIVE Three children with a history of recurrent infections since infancy were found to have MBL deficiency associated with a neutrophil chemotactic unresponsiveness specific to C5a. We have studied the genomic sequence of the C5a receptor (C5aR) in 2 of the subjects to determine whether this unresponsiveness was due to a genetic mutation or to aberrant complement activation associated with the MBL deficiency. METHODS MBL genotype analysis was performed by PCR-based methods with use of specific primers and restriction enzymes to detect the 3 previously reported mutations. Expression of C5aR was analyzed by flow cytometry. The C5aR gene was amplified from the patients genomic DNA by PCR and sequenced by standard procedures. RESULTS C5aR was found to be expressed normally on the neutrophils of one of the subjects. Sequence analysis of the C5aR gene revealed a point mutation that substituted threonine at position 261 for alanine in one patient but no abnormality in the other, suggesting gene polymorphism. Treatment of 2 patients with granulocyte-colony stimulating factor corrected the neutrophil chemotactic abnormality in vitro and induced a significant clinical improvement. CONCLUSION MBL deficiency can be associated with neutrophil chemotactic unresponsiveness to C5a and it is clinically manifested by recurrent and chronic infections. Treatment of these patients with granulocyte colony-stimulating factor results in normalization of neutrophil chemotaxis against C5a and significant clearing of infections.