[Can asthma deaths in young people be predicted and prevented?]. / Kan astmadöd hos unga förutses och förebyggas?

UNLABELLED: In spite of increased asthma prevalence, the mortality in the disease has decreased during the last two decades in Sweden and in some other countries. However, in the age group 15-24 years an increased death rate was noted at the end of the 1980s. Therefore we started a prospective study from 1994 with the aim of trying to analyse the precipitating factors of all deaths in the ages 1-34 years in which the death certificate alleged asthma or anaphylaxis as the main or contributing cause of death. We conducted a confidential telephone enquiry of the next of kin of the deceased using a modified questionnaire developed by the British Thoracic Association. When available, patient records and post mortem protocols were obtained. RESULTS: The mortality in asthma in the ages 1-34 years has decreased from around 5 per million/year to 0.5/million/year over the period 1987-1998. The main preventable factors found in this analysis are undertreatment, non-compliance, psychosocial factors including alcohol/drug abuse, food allergy and inhalation allergy. Lacking awareness of the risks and underestimation of the severity of the asthma both by the physician and the patient seem to be dominating factors.

Spectrum of extracellular matrix degrading enzymes in normal and malignant T lymphocytes.

Human T cells produce and release fibronectin degrading neutral serine proteases with a molecular weight of 50 kD, 70-80 kD (doublet) and 95 kD and have a cell associated 400 kD fibronectin degrading enzyme. In addition, human T cells produce proteases with m.w. 50, 70-80 kD and 400 kD which degrade laminin. CD 4+ T lymphocytes from a non-malignant cloned human T cell line produce a 92 kD gelatinase (MMP 9) and malignant T cell lines release, in addition to the 92 kD gelatinase, low amounts of a 72 kD gelatinase (MMP 2). Purification of the enzymatic activities using benzamidine sepharose yields a 50 kD and a 70 kD band of which the 50 kD band has fibronectin degrading capacity. The purified enzymes do not react with monoclonal antibodies to various previously characterized proteolytic enzymes present in T cells. T lymphocytes from a non-malignant cloned human T cell line produce high amounts of the 50 and 70-80 kD proteases directly after stimulation with anti-CD 3 monoclonal antibodies whereafter the production of these enzymes declines with time. The expression of the 400 kD fibronectin-degrading protease is downregulated by crosslinking of alpha 4 beta 1-integrin receptors on T cells using monoclonal antibodies. Thus, T lymphocytes produce several matrix degrading enzymes with multiple substrate specificities. The expression of these enzymes is controlled partly by lymphocyte activation signals or by direct signalling via beta 1-integrins.

Lack of T-lymphocytosis and poor interferon gamma production in BAL fluid from HIV-negative immunocompetent patients with pulmonary non-tuberculous mycobacteriosis.

Very little is known about the pathogenesis of pulmonary non-tuberculous mycobacteriosis in immunocompetent individuals. Local inflammatory response was assessed by examining bronchoalveolar lavage fluid from 13 HIV-negative patients (12 F) without known cell-mediated immunosuppression, aged 48-72 y (median age 60 y), with non-tuberculous lung mycobacteriosis. Macrophages, lymphocytes, polymorphonuclear neutrophils and eosinophils in bronchoalveolar lavage fluid were analysed morphologically, and the subsets of T-lymphocytes (CD3+, CD4+, CD8+), HLA-DR+, B-lymphocytes (CD19+) and CD16+/CD56+ cells (natural killer, NK cells) were analysed by flow cytometry. Interleukin-1 beta (IL-1beta), IL-2, IL-4, IL-6, IL-8, IL-10 and interferon-gamma (IFN-gamma) levels were assessed by ELISA. The total number of cells/ml was significantly higher in BAL fluid from the patients (median value=880 x 10(3)/ml) compared to six healthy controls (200 x 10(3)/ml). The polymorphonuclear neutrophil population was significantly increased in the patients both proportionally and in the count/ml. The proportion of macrophages was significantly reduced in the patients but not the count/ml. The count of lymphocytes/ml was significantly higher in the patients but the proportion of lymphocytes was unchanged. No significant difference was seen in the relative proportion of NK cells, B- or T-lymphocytes and HLA-DR+ compared to the healthy controls. The IL-1beta and IL-8 levels were significantly increased in the patients. No differences were seen between the patients and controls in the leukocyte or lymphocyte subsets in peripheral blood. The local inflammatory response in BAL fluid from the studied patients was characterized by granulocytosis, and increase in the IL-1beta and IL-8 levels. There was no specific T-cell response.

Triggering of motile behavior in T lymphocytes via cross-linking of alpha 4 beta 1 and alpha L beta 2.

The mechanisms by which T lymphocytes are transformed from passively transported cells during circulation in the vascular system to actively migrating cells during extravasation are unknown. Therefore, the possibility that lymphocyte receptors are capable of inducing motility was investigated using a modified Boyden chamber assay. Cross-linking of alphaL beta2 and alpha4 beta1 on human T lymphocytes (T cell line and peripheral blood T cells) with immobilized mAbs induced motile behavior on fibronectin, laminin, collagen type IV, and poly-L-lysine. This induction of T cell migration was very potent and in most cases more efficient than pretreatment of the cells with phorbol esters. In contrast, control Abs to several other integrin- and non-integrin molecules present on T lymphocytes did not induce T cell migration. Anti-CD3 Abs themselves did not trigger motile behavior. However, anti-CD3 promoted T cell migration in the Boyden chamber system if present simultaneously with 40-kDa alpha4 beta1 binding fibronectin fragments or alphaL beta2 binding intercellular adhesion molecule-1/hIgG1Fc fusion proteins on the upper side of the filter. Abs to other surface components on T cells did not trigger motility when presented together with the 40-kDa fibronectin fragments or the intercellular adhesion molecule-1/hIgG1Fc fusion proteins. The induction of motile behavior could be blocked if the T cells were pretreated with Genistein and Calphostin C, indicating the involvement of a protein tyrosine kinase and protein kinase C-dependent signaling pathway in triggering of T cell motility via integrins. These results indicate that alphaL beta2 and alpha4 beta1 on T lymphocytes can selectively trigger motile behavior when cross-linked by their endothelial or extracellular matrix ligands. Furthermore, these data indicate that cross-linking of CD3 facilitates ligand binding and subsequent triggering of a motile phenotype by alphaL beta2 and alpha4 beta1.

Fungal pneumonia: the predominant lung infection causing death in children undergoing bone marrow transplantation.

The study included 6 children (aged 4-14 years) receiving a conditioning regimen for bone marrow transplantation (BMT) and 14 children (aged 2 14 years) with bone marrow transplants (13 allogeneic, 1 autologous). The children underwent flexible fibre-optic bronchoscopy (FFB) with bronchoalveolar lavage during 6 and 17 episodes of pneumonia, respectively. The aim was to compare the results of the two groups with respect to bronchoscopy findings, pneumonia-causing agents and outcome. During the conditioning regimen, the aetiological agents were recovered by bronchoscopy in 1/6 (17%) episodes and revealed by autopsy in another episode. In three episodes where the aetiology was uncertain, bacterial pneumonia was suspected in two, and Candida pneumonia in one. In episodes after transplantation the aetiological agents were recovered from bronchoscopy material in 14/17 (82%) patients. Autopsy confirmed the premortal diagnosis in the four children who died. In three episodes, bacterial pneumonia was clinically suspected. Based on clinical manifestations, FFB and autopsy findings, bacterial and fungal pneumonia were the most common diagnoses both during conditioning and after BMT. Fungal pneumonia was the most common cause of death in both groups.

T lymphocyte migration: the influence of interactions via adhesion molecules, the T cell receptor, and cytokines.

Although lymphocytes have been studied extensively with respect to a number of motile aspects the understanding of directed lymphocyte motility and its regulation has increased relatively slowly. T lymphocyte migration/translocation in vivo and in vitro are critically dependent on the avidity of adhesive lymphocyte receptors for endothelial cell ligands and extracellular matrix (ECM) components and on the capacity of the lymphocytes to undergo a motile response. Lymphocytes are rendered motile by adhesion to endothelial cells and ECM components. Thus, T lymphocytes exhibit chemotactic and haptotactic migration to the ECM components fibronectin, laminin, and collagen type IV. This directed migration is mediated by beta 1-integrins and separate T-lymphocyte lines have a functional specialization using either alpha 4 beta 1 or alpha 5 beta 1 during chemo- and haptotaxis to ECM components, although the same cell line may use both integrins for adhesion. Noteworthy, signals triggering T cell migration to ECM components seem to be delivered preferentially via alpha 4 beta 1 or alpha L beta 2. The T cell antigen receptor cannot by itself trigger T lymphocyte migration to fibronectin, laminin, or collagen type IV but does so in collaboration with signals via alpha 4 beta 1. It follows that the migration-triggering signals can be separated from the integrin interactions with matrix components that mediate the chemo- and haptotactic migration per se. This suggests that T cell recruitment to inflammatory sites is induced by antigen receptor signals and beta 1- and beta 2-integrin signals in synergy. Cytokines with chemokinetic properties may collaborate with lymphocyte counterreceptors on endothelial cells and with ECM components in control of the lymphocyte migratory pathways and specifically attract lymphocyte subsets to different compartments. T lymphocytes are endowed with multiple enzymes, classified as serine proteinases or metalloproteinases, which can degrade extracellular matrix components. These enzymes may play an important role for the capacity of T cells to migrate and infiltrate tissues.

T lymphocyte infiltration of two- and three-dimensional collagen substrata by an adhesive mechanism.

Lymphocytes were plated on two-dimensional (2D) and three-dimensional (3D) collagen substrata and their distribution and behavior determined using light and scanning electron microscopy. When allowed to settle on 2D collagen substrate T-lymphocytes "rapidly" attached and penetrated and thus virtually never remained attached on top of the collagen. As a consequence of this penetration the cells appeared below the collagen. In contrast to lymphocytes, fibroblasts and macrophages allowed to settle on 2D collagen did not penetrate but underwent cytoplasmic spreading on top of the collagen. Lymphocyte attachment and penetration of 2D collagen was specifically inhibited by monoclonal antibodies to beta 1-integrins, indicating that the process depends on molecular adhesion to the collagen. The penetration of 2D collagen appeared to consist of tight binding of collagen fibers to the cells, local reorganization of the collagen carpet, and redistribution of the cell-attached collagen fibers from the "lower" to the "upper" pole/surface of the lymphocyte. Lymphocyte infiltration of 3D collagen substrata was also specifically inhibited by monoclonal antibodies to beta 1-integrins. During the infiltration of 3D collagen lymphocytes exhibited collagen fibers attached to their surface and seemed to provoke perturbation of the collagen. These results show that T lymphocytes are programmed to penetrate and perturb 2D and 3D collagen substrata by a mechanism dependent on adhesive interaction. However, deattachment tends to counteract persistent binding of the cells to 2D collagen.

T lymphocytes degrade fibronectin.

Mononuclear cells cause disappearance of fibronectin synthesized and released by fibroblasts. This disappearance of extracellular fibroblast fibronectin is accompanied by the appearance of components of 'lower' molecular weight indicating that a fibronectin-degrading enzymatic activity is responsible for the effect. Additional support for the existence of a fibronectin-degrading enzyme is that mononuclear cells degrade iodinated fibronectin attached to a collagen matrix. Furthermore, lymphocytes seem to mediate the degradation of fibronectin whereas monocytes rather act inhibitory.