Operation Everest II: Alterations in the immune system at high altitudes

We investigated the effects on immune function after progressive hypobaric hypoxia simulating an ascent to 25,000 ft (7620 m) over 4 weeks. Multiple simultaneousin vitro andin vivo immunologic variables were obtained from subjects at sea level, 7500 ft (2286 m), and 25,000 ft during a decompression chamber exposure. Phytohemag-glutinin-stimulated thymidine uptake and protein synthesis in mononuclear cells were reduced at extreme altitudes. Mononuclear-cell subset analysis by flow cytometry disclosed an increase in monocytes without changes in B cells or T-cell subsets. Plasma IgM and IgA but not IgG levels were increased at altitudes, whereas pokeweed mitogen-stimulatedin vitro IgG, IgA, and IgM secretion was unchanged. During exposure to 25,000 ft,in vitro phytohemagglutinin-stimulated interferon production and natural killer-cell cytotoxicity did not change statistically, but larger intersubject differences occurred. IgA and lysozyme levels (nasal wash) and serum antibodies to nuclear antigens were not influenced by altitude exposure. These results suggest that T-cell activation is blunted during exposure to severe hypoxemia, whereas B-cell function and mucosal immunity are not. Although the mechanism of alteredin vitro immune responsiveness after exposure to various environmental stressors has not been elucidated in humans, hypoxia may induce alterations in immune regulation as suggested byin vitro immune assays of effector-cell function.Some of this study's results were presented as an abstract at the FASEB meeting in St. Louis, Missouri, 1986.     

A 3 year retrospective review of intrauterine insemination, using cryopreserved donor spermatozoa and cycle monitoring by urinary or serum luteinizing hormone measurements

Insemination with donor spermatozoa is an integral part of infertility treatment. For the last 3 years in our unit, intrauterine insemination with donor spermatozoa (IUID) has been used in preference to vaginal insemination. In this retrospective study, patients were offered an initial course of five single intrauterine inseminations with cryopreserved donor spermatozoa and treatment was then reviewed. A total of 389 patients received 1465 inseminations. In all, 1119 cycles were monitored using luteinizing hormone serum analyses and 346 cycles using the urine home test kits. The clinical pregnancy rate per insemination for the cycles monitored by the serum assay was 18.0% (202/1119) compared with the urine cycles (13.7%, 46/346) (P <05). The pregnancy loss rate was not significantly different (14.4%, 29/202 and 21.7%, 10/46) (serum and urine cycles respectively). The viable clinical pregnancy rate was significantly higher (P <03) for the serum cycles than for the cycles using the urinary monitoring (15.5%, 173/1119 and 10.4%, 36/346 respectively). The cycles monitored by serum assay had a significantly higher cumulative viable clinical pregnancy rate (P <0001) of 70.2% after nine inseminations compared with the urine monitored cycles of 54.8%. The majority of patients opted for the serum cycles, with a minority self-selecting the urine cycles mainly for travelling convenience. The explanation for the significant differences between the viable clinical pregnancy rates per insemination and the cumulative viable clinical pregnancy rates may be due to the sensitivity of the urine home test kit or the patients' interpretation of the result.      

Fertility rates in female patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency

Among 80 women with congenital adrenal hyperplasia due to 21-hydroxylase deficiency (40 with the simple virilizing form and 40 with the salt-losing form), 40 reported having an adequate introitus and being heterosexually active. In 15 of 25 patients with the simple virilizing form, 25 pregnancies resulted in 20 normal children, whereas only 1 of 15 women with the salt-losing form became pregnant; this pregnancy was electively terminated. Several factors seem to be responsible for the low fertility rates: noncompliance with therapy was probably high, as suggested by hirsutism and poor endocrine follow-up in 25 percent of patients; whereas 49 patients had regular menstrual periods, 14 had irregular periods, 10 had amenorrhea, 5 had undergone hysterectomy, and 2 had entered menopause; 87 percent of patients with salt loss and 50 percent of those with simple virilization (P less than 0.001) had remained single; the vaginal introitus was reported to be inadequate for intercourse by 35 percent of patients (53 percent of those with salt loss and 18 percent of those with simple virilization; P less than 0.002); and heterosexual activity was reported less frequently among patients with an inadequate introitus. The status of the introitus seemed to have a more important role in the sexual activity reported than did the degree of prenatal exposure to androgen (which was higher among patients with salt loss than among those with simple virilization). However, our data did not rule out an effect of androgen exposure on female fetuses. Our experience indicates that improved surgical correction of the external genitalia and better compliance with therapy will be necessary to improve fertility rates among women with congenital adrenal hyperplasia due to 21-hydroxylase deficiency.     

Mutation of the gene encoding fibrillin-2 results in syndactyly in mice

Fibrillins are large, cysteine-rich glycoproteins that form microfibrils and play a central role in elastic fibrillogenesis. Fibrillin-1 and fibrillin-2, encoded by FBN1 on chromosome 15q21.1 and FBN2 on chromosome 5q23-q31, are highly similar proteins. The finding of mutations in FBN1 and FBN2 in the autosomal dominant microfibrillopathies Marfan syndrome (MFS) and congenital contractural arachnodactyly (CCA), respectively, has highlighted their essential role in the development and homeostasis of elastic fibres. MFS is characterized by cardiovascular, skeletal and ocular abnormalities, and CCA by long, thin, flexed digits, crumpled ears and mild joint contractures. Although mutations arise throughout FBN1, those clustering within exons 24-32 are associated with the most severe form of MFS, so-called neonatal MFS. All the mutations described in CCA occur in the "neonatal region" of FBN2. Both MFS and CCA are thought to arise via a dominant negative mechanism. The analysis of mouse mutations has demonstrated that fibrillin-1 microfibrils are mainly engaged in tissue homeostasis rather than elastic matrix assembly. In the current investigation, we have analysed the classical mouse mutant shaker-with-syndactylism using a positional candidate approach and demonstrated that loss-of-function mutations outside the "neonatal region" of Fbn2 cause syndactyly in mice. These results suggest that phenotypes distinct from CCA may result in man as a consequence of mutations outside the "neonatal region" of FBN2.     

B lymphocytes secreting IgG linked to latent transforming growth factor- beta prevent primary cytolytic T lymphocyte responses

B lymphocytes secreting IgG linked to latent transforming growth factor (TGF)-beta (IgG-TGF-beta) prevent cytolytic T lymphocyte (CTL) responses to unrelated antigens in mixed lymphocyte cultures (MLC) so long as resting resident macrophages and functional Fc receptors are present. This was shown using IgG-secreting plaque-forming cells (PFC) to sheep erythrocytes (SRBC) obtained from popliteal lymph nodes of mice injected repeatedly in foot pads with SRBC. Remarkably, as few as approximately 300 PFC prevented CTL responses of 5 x 10(5) normal syngeneic spleen cells in MLC. Supranatants of short-term cultures of PFC also prevented CTL responses, and suppression was prevented by eliminating or dissociating IgG and TGF-beta present in supranatants or by antibody against active TGF-beta. Furthermore, the latency- associated peptide of latent TGF-beta was detected in approximately 10% of foci of IgG captured from single PFC, indicating that at least some B lymphocytes secrete IgG-TGF-beta as a complex. Resting resident macrophages (which do not produce latent TGF-beta) and functional Fc receptors were required for suppression, consistent with idea that IgG- TGF-beta is taken up through Fc receptors for IgG and that active TGF- beta, cleaved from latent TGF-beta of the complex, is delivered directly to potentially responding CTL. If CTL responses in man are similarly regulated by B lymphocytes, then an ongoing B cell response in patients with chronic viral infections or bearing immunogenic cancers may prevent effective therapeutic vaccination.      

Cross-presentation: underlying mechanisms and role in immune surveillance

Summary: It was originally thought that a cell's major histocompatibility complex (MHC) class I molecules presented peptides derived exclusively from proteins synthesized by the cell itself. However, in some circumstances, antigens from the extracellular environment can be presented on MHC class I molecules and stimulate CD8⁺ T‐cell immunity, a process termed cross‐presentation. Cross‐presentation was originally discovered as an obscure phenomenon in transplantation immunity. However, it is now clear that it is a major mechanism by which the immune system monitors tissues and phagocytes for the presence of foreign antigen. Cross‐presentation is the only pathway by which the immune system can detect and respond to viral infections or mutations that exclusively occur in parenchymal cells rather than in bone marrow‐derived antigen‐presenting cells (APCs). Professional APCs, such as dendritic cells, are the principal cells endowed with the capacity to cross‐present antigens. In this process, the APCs acquire proteins from other tissue cells through endocytic mechanisms, especially phagocytosis or macropinocytosis. The internalized antigen can then be processed through at least two different mechanisms. In one pathway, the antigen is transferred from the phagosome into the cytosol, where it is hydrolyzed by proteasomes into oligopeptides that are then transported by the transporter associated with antigen processing to MHC class I molecules in the endoplasmic reticulum or phagosomes. In a second pathway, the antigen is cleaved into peptides by endosomal proteases, particularly cathepsin S, and bound by class I molecules probably in the endocytic compartment itself. Depending on the nature of the antigen, one or both of these pathways can contribute to cross‐presentation in vivo. The outcome of cross‐presentation can be either tolerance or immunity. Which of these outcomes occurs is thought to depend on whether antigens are acquired by themselves alone, leading to tolerance, or with immunostimulatory signals, leading to immunity. One source of such signals is from dying cells that release immunostimulatory ‘danger’ signals that promote the generation of immunity to their cellular antigens. In addition to the critical role of cross‐presentation in normal immune physiology, this pathway has considerable potential for being exploited for developing subunit vaccines that elicit both CD4⁺ and CD8⁺ T‐cell immunity.     

Neutralizing antibodies to African swine fever virus proteins p30, p54, and p72 are not sufficient for antibody-mediated protection

Although antibody-mediated immune mechanisms have been shown to be important in immunity to ASF, it remains unclear what role virus neutralizing antibodies play in the protective response. Virus neutralizing epitopes have been identified on three viral proteins, p30, p54, and p72. To evaluate the role(s) of these proteins in protective immunity, pigs were immunized with baculovirus-expressed p30, p54, p72, and p22 from the pathogenic African swine fever virus (ASFV) isolate Pr4. ASFV specific neutralizing antibodies were detected in test group animals. Following immunization, animals were challenged with 10(4) TCID(50) of Pr4 virus. In comparison to the control group, test group animals exhibited a 2-day delay to onset of clinical disease and reduced viremia levels at 2 days postinfection (DPI); however, by 4 DPI, there was no significant difference between the two groups and all animals in both groups died between 7 and 10 DPI. These results indicate that neutralizing antibodies to these ASFV proteins are not sufficient for antibody-mediated protection.