ABSTRACT
People encounter respirable particulate antigens in a vast variety of environments, but the dose and duration of exposure are not usually sufficient to induce complete sensiti zation. As noted below, many individuals with appropriate exposure will evidence a hu moral immune response (serum antibody), and some may even demonstrate cell-mediated immune responses (lymphocyte transformation) with no clinical features of disease. Most of the occupations, hobbies, or living environments that produce HP create exposures to distinctive antigenic materials that involve repeated high-dose inhalation and/or prolonged contact. The agents that cause HP can be grouped broadly into three categories: microbio logical agents, proteins, or chemicals. Many of these occur in distinctive work environ ments, and HP in those settings has been labeled with the name of the job. Table 1 lists a selection of these conditions.
