Activation of CD4+ T cells, increased TH2-type cytokine mRNA expression, and eosinophil recruitment in bronchoalveolar lavage after allergen inhalation challenge in patients with atopic asthma

Peripheral blood T lymphocytes in seasonal bronchial asthma

Variations in T lymphocytes in asthmatic patients are related to disease severity. However, the effects of natural exposure to pollens on peripheral blood T lymphocytes have not been clarified. In this paper, the effects on peripheral blood CD4 and CD8 lymphocytes from pollen-sensitive subjects and from nonatopic donors were studied during and outside the pollen season. In patients who suffer from seasonal asthma, we found an increase in the CD4/CD8 bright ratio and a decrease in the mean number of CD4 receptors per cell during the pollen season. No variation was observed in healthy subjects. These results suggest that CD4 lymphocytes may be causally linked to the pathogenesis of seasonal bronchial asthma.

Immunocompetent cells of the upper airway: functions in normal and diseased mucosa

Secretory immunity is central in primary defense of the airway mucosa. B cells involved in this local immune system are initially stimulated in mucosa-associated lymphoid tissue, including tonsils and adenoids, and then migrate to secretory effector sites where they become immunoglobulin (Ig)-producing plasma cells. Locally produced Ig consists mainly of J-chain-containing dimers and larger polymers of IgA (pIgA) that are selectively transported through glandular cells by an epithelial receptor called secretory component or pIgR. Secretory antibodies perform surface protection by immune exclusion of soluble antigens as well as infectious agents. IgG can also participate in this primary defense because it reaches secretions by passive diffusion similar to IgE. However, the inflammatory properties of antibodies belonging to the latter two classes explain their involvement in mucosal immunopathology when elimination of penetrating antigens is unsuccessful. T helper (Th) cells activated in this process may by a Th2 profile of cytokines promote persistent inflammation with extravasation and priming of eosinophils. This mechanism appears to occur in the late-phase allergic reaction, perhaps driven mainly by interleukin-4 (IL-4) released from mast cells subjected to IgE-mediated degranulation. Eosinophils are potentially tissue-destructive cells, particularly after priming with IL-5. Cytokines also up-regulate adhesion molecules on vascular endothelium and epithelium, thereby enhancing migration of eosinophils and other leukocytes into the mucosa.(ABSTRACT TRUNCATED AT 250 WORDS)

The airway inflammatory response in allergic asthma and its relationship to clinical disease

Endobronchial biopsy and lavage studies have revealed the presence of mast cell, eosinophil, T-lymphocyte and epithelial cell activation in asthma, along with the structural changes of tissue eosinophil infiltration, loss of superficial columnar ciliated epithelial cells and enhanced collagen deposition in the laminar reticularis. As these cellular and structural changes underlie the clinical features of asthma, i.e., symptom expression, variable airflow obstruction and bronchial hyperresponsiveness, and understanding of their induction and regulation is essential to the understanding of the asthmatic process. The acute airway response to allergen has been studied by the technique of local endobronchial allergen challenge with direct airway sampling in asthma. These studies identify allergen-mast cell interaction as the initial airway event, with mediator release inducing bronchoconstriction and enhancing vascular permeability. As preformed cytokines are present in mast cells, cytokine release from this cell population is likely to initiate the process of endothelial cell activation, with upregulation of cell adhesion molecules, and tissue cell recruitment. Subsequent cytokine elaboration from airway macrophages and T-lymphocytes will perpetuate this response while in chronic clinical disease T-lymphocytes, mast cells, matrix tissue, epithelial cells and eosinophils themselves are all likely to contribute to the cytokine pool within the airways and thus to the regulation of inflammatory cell migration and activation.

The role of eosinophils in the pathogenesis of asthma

The eosinophil is regarded as a key mediator of the pathology and abnormal physiology of bronchial asthma. Current investigations are directed at understanding how eosinophils are attracted into the respiratory tract and how they bring about the abnormalities characteristic of this disease.

Detection of interleukin-5 messenger RNA and interleukin-5 protein in bronchial biopsies from asthma by nonradioactive in situ hybridization and immunohistochemistry

Recently direct evidence for the role of interleukin-5 (IL-5) in eosinophilic inflammation in the airways of persons with asthma has been provided by an in situ hybridization study that used radioisotope-labeled IL-5 complementary RNA probes. Radioisotope-labeled probes, although sensitive, require autoradiographic detection, which is time-consuming. In the most recent study we attempted to detect IL-5 messenger RNA in the bronchial biopsy specimens from patients with asthma using nonradioactive in situ hybridization, which gives rapid results. Bronchial biopsy specimens were obtained from eight patients with asthma and seven diseased control subjects. IL-5 complementary DNA probes were labeled with digoxigenin-deoxyuridine triphosphate and hybridized to permeabilized sections. Hybridization signals were visualized by an immunohistochemistry technique. Positive hybridization signals were observed in six of the eight biopsy specimens from patients with asthma. Pretreatment with ribonuclease or hybridization with an unrelated probe produced negative results. Immunohistochemical staining of serial sections with a monoclonal antibody to IL-5 revealed that a few cells within the mucosa positively stained, suggesting active synthesis of IL-5. Biopsy results from the seven diseased control subjects did not show any hybridization signal. These results confirm and extend previous observations of IL-5 messenger RNA expression in the airways of patients with asthma, and suggest that digoxigenin-labeled IL-5 complementary DNA probes would be a powerful research tool.

Modern concepts of immunotherapy

Although common allergies have been considered as immediate IgE antibody mediated responses, attention is now turning to inflammatory responses that appear to be initiated by T-cell responses to peptides from allergens presented in combination with HLA class II molecules. Although classic immunotherapy with allergen extracts has been found to downregulate these T-cell responses, more efficient and safe methods are being sought.