Thus, within the skin of man, the evidence is strong that late responses to antigen can be dependent on IgE. The hypothesis that late phase reactions within the airways may also depend on IgE is more difficult to study in man. A recent report by Kirby et al did find that inhalation of sheep anti-human IgE led to LAR in one atopic asthmatic patient. With use of a rabbit model of the LAR, the importance of antigen-specific IgE and IgG to this pattern of airway obstruction has been investigated in more detail. In a study involving neonatal immunization to Altemaria tenuis, rabbits with predominantly or only IgE to this mold developed both early and late airway obstruction. When rabbits were passively sensitized with intravenous infusions of sera containing IgE to this antigen, late responses were again noted.
In both actively and passively sensitized rabbits, antigen-specific IgG appeared to blunt the LAR in immune rabbits. Evaluation of histologic specimens did not show evidence of immunoglobulin and complement deposition in the lungs of rabbits with late responses. Recent studies employing guinea pig models of the late asthmatic response also suggested antigen-specific IgE may be more important than antigen-specific IgG in producing LARs in this species. Thus, as in human skin, the lungs of man, rabbits, and guinea pigs can develop antigen-induced, IgE-associated alterations in airway function hours after antigen exposure. alesse birth control
Late phase responses within the lower airways have been reported after exercise, a nonimmunologic stimulus, and after exposure to occupational agents when the subject had no demonstrable IgE to the agent. While the true incidence of exercise-induced LARs and the significance of the mediators found after exercise are subjects of debate, it does appear that an IgE-dependent mechanism is only one of perhaps several ways in which late-onset airway obstruction may be precipitated.
Tags: airway, Asthma, phase reactions