The past 10 to 15 years have brought increased recognition of the importance of indoor allergens—in particular, of protein allergens—in generating allergic responses and asthma (Burge and Platts-Mills, 1991a; Burrows et al., 1989; Platts-Mills et al., 1991a). In part, this recognition is based on an awareness of the clinical significance of the increased time spent by modern humans indoors (Spengler and Sexton, 1983). This increased exposure has led to assessments of the potential contribution of proteins inhaled in the indoor environment to the pathogenesis of several allergic conditions, including allergic rhinitis, sinusitis, allergic conjunctivitis, asthma, and hypersensitivity pneumonitis. This chapter addresses the basic mechanisms of cellular, tissue, and airway responses to inhaled proteins. It seeks to use these responses as a framework to plan control strategies based on patterns of exposure and epidemiology.

RESPONSE OF AIRWAY CELLS AND TISSUES TO INDOOR ALLERGENS

This section discusses the resident cells and tissues that are involved in airway host responses; the discussion is organized on the basis of the structure of the upper and lower airways. A second topic is the function of immune and inflammatory cells that may infiltrate resident cells and tissues of these airways in response to an immune reaction directed against inhaled protein allergens. Table 4-1 identifies the cells of the airway and highlights their effector function (i.e., the action they take against a target cell). The

TABLE 4-1 Structural and Inflammatory Characteristics of Cells of the Airway

Cell

Effector Function

Epithelial

APC, cytokines, mediators

Endothelial

APC, cytokines, mediators

Smooth muscle

Bronchial tone, cytokines, mediators

Fibroblasts

Cytokines, mediators, growth factors

Macrophages

APC, cytokines, mediators

Dendritic cells

APC, cytokines, mediators

T cells

Cytokines, specific response (TCR)

B cells

APC, Ig production, mediators

Mast cells

Cytokines, mediators, specific responses (IgE)

Eosinophils

Cationic proteins, cytokines, mediators

Neutrophils

Enzymes, cytokines, mediators

Neuroepithelial cells

Neuropeptides

NOTE: APC, antigen-presenting cells; Ig, immunoglobulin; and TCR, T cell receptor.



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