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Immune complexes (bovine serum albumin with rat antibodies to bovine serum albumin) formed in twofold antibody excess were injected into the duodenum of normal rats. In comparison to controls injected with antigen only, there was a marked increase in the percentage of disrupted goblet cells (an index of mucus release) in segments from the intestine of rats exposed for 3 hours to immune complexes in vivo. Similarly, there was a significant increase in 35S-labeled mucus recovered by filtration of intestinal wash, rinse, and mucosal homogenate fluids from rats exposed to immune complexes compared to those from rats exposed to bovine serum albumin or purified rat antiserum to bovine serum albumin alone. These findings suggest that certain immune complexes can stimulate mucus release from intact rat small intestine; enhanced mucus release may have a role in clearing the surface of complexes.

Summary Eight commercial cat dander extracts and two pelt extracts derived from mongrel and Siamese cats were compared. Cat allergen 1 and cat albumin were measured by radial immunodiffusion. Allergenic activity was evaluated by prick test and a modified radioallergosorbent test. In the latter, the dilution of each extract that produced 50% inhibition of binding of IgE antibodies to insolubilized cat allergen 1 (RAST 1) and insolubilized cat serum (RAST 2) was determined. The total non‐dialysable solid content of the extracts did not correlate with any other parameter. Cat allergen 1 content determined by radial immunodiffusion correlated with average prick test results in ten cat‐sensitive subjects and with RAST 1 activity. Cat albumin content correlated weakly with RAST 2 activity but not with any other measure of allergenic activity. Absorption of each extract with the γ‐globulin fraction of rabbit antiserum to cat allergen 1 significantly reduced prick test reactivity and RAST 1 activity, but not RAST 2 activity. These results indicate that cat allergen 1 is an important allergen in cat dander extracts and its measurement may be used to standardize the allergenic activity of such extracts.