Lymphocytes, key cells in chronic inflammation, are increased in the airways of asthmatics and have increased expression of the interleukin-2 (IL-2) receptor, a sign of activation. We determined the effects of depleting cells bearing IL-2 receptors on immunoglobulin (Ig) production, airway inflammation, and airway responses after antigen challenge of Brown Norway rats that were sensitized to ovalbumin (OA). Both control and ART-18 (antirat IL-2 receptor) antibodies inhibited plasma specific IgE and the early (ER) and late (LR) airway responses to antigen when given from zero to 14 d after sensitization. When ART-18 was administered from 4 to 14 d after sensitization and compared with control animals, it inhibited OA specific IgE production from Day 21 onward, but it increased total IgE and specific IgG. These changes followed a significant increase in blood CD4+ lymphocytes (%) in ART-18-treated animals 14 d after sensitization. The same protocol of administration did not affect Ig levels at 14 d, but it decreased neutrophil influx into the lungs 8 h after antigen challenge without any effects on the ER and LR. Administration of ART-18 at the time of antigen challenge did not affect the subsequent airway inflammation or the increased responsiveness to methacholine that occurs 32 h after antigen challenge. In summary, depletion of IL-2-receptor-bearing cells affects lymphocyte subsets and immunoglobulin production and it decreases the influx of neutrophils into the lungs 8 h after OA challenge, but it does not significantly inhibit the ER, LR, or increased airway responsiveness after antigen challenge.