Control (nonragweed-immune) rabbits had neither immediate nor late responses after exposure to this antigen, while ragweed-immune rabbits had early and late decreases in lung function. In addition, marked increases in airway reactivity to histamine were noted in the ragweed-immune group. These observations suggest that the granulocytic series of cells is important in the production of the LAR and the subsequent increase in airway reactivity in this model.
Potential Mediators of the LAR
In terms of the mediators of inflammation and immediate hypersensitivity that may be important in late phase reactions, studies in sheep have strongly suggested that lipoxygenase products of arachidonic acid metabolism are important in producing LAR. However, Britton and co-workers found that an oral leukotriene D4 antagonist led to a small reduction in the immediate asthmatic response after antigen challenge of atopic asthmatics but had no significant effect on the LAR. Thus, the potential importance of lipoxygenase products of arachidonic acid metabolism in human LARs remains to be explored in more detail. buy actos 30mg
Other mediators have also been associated with late phase reactions. For example, Dorsch and co-workers performed studies that suggest that thromboxanes may be involved in late cutaneous reactions in man. In the upper airways, Naclerio and associates2 found histamine, TAME-esterase, kinin, and prostaglandin D2 were all released during the immediate response to antigen, but only the first three were released during late responses, leading to speculation that basophils were the cellular source of the mediators during the late response. Another mediator that has attracted much attention in terms of late phase reactions has been platelet-activating factor (PAF). While administration of PAF to humans led only to LARs, Cuss et al reported that PAF increased airway reactivity. As reviewed earlier, this may be one of the most important consequences of an LAR. Thus, at present, the relative importance of various mediators in terms of late phase reactions remains to be studied in more detail.
Tags: airway, Asthma, phase reactions