Importance of Inflammatory Cells In LAR
Late phase reactions in man and animal models have been associated with inflammation within the involved tissue. In terms of LAR, bronchoalveolar lavages performed after antigen challenges that led to LARs have shown accumulations of inflammatory cells. For example, de Monchy et al found the LAR was associated with accumulation of eosinophils in the lung, while Metzger et al found that lavage fluids contained both neutrophils and eosinophils during the late time period. In actively immunized rabbits with IgE to Altemaria tenuis, simultaneous challenge of the skin and lungs led to interstitial edema and vessel dilation in the skin and airways within 15 to 30 minutes of exposure, while the late time period (six hours) was characterized by edema and a mixed cellular infiltrate of polymorphonuclear leukocytes (neutrophils and eosinophils) and mononuclear cells. These abnormalities were found in both large and small airways. Forty-eight hours after antigen challenge the edema had subsided, and the cellular infiltrate was more nearly mononuclear in character. After seven days, the histology of both skin and airways was normal.

In man and in rabbits, LAR and accumulation of granulocytes within the airways have been temporally related. In addition, in rabbits, the subsequent increase in airway reactivity has been associated with an increase in inflammatory cells within bronchoalveolar lavage fluid. However, this temporal association does not necessarily mean that accumulation of cells and release of mediators were responsible for the late response and/or subsequent increase in airway reactivity. The importance of granulocytes to the antigen-induced LAR in rabbits has been documented by depletion and partial repletion of these cells. In immune rabbits made neutropenic with the administration of nitrogen mustard, subsequent antigen challenge led to an IAR, but no LAR or increase in airway reactivity. To determine if this effect was truly due to granulocyte depletion, and not an unrelated effect of nitrogen mustard, granulocytopenic ragweed-immune and granulocytopenic ragweed-nonimmune rabbits were transfused with a neutrophil-rich population of white cells at the time of ragweed exposure.