The Role of Immunotherapy in Cockroach Asthma

Abstract

To evaluate the preventive role of immunotherapy in severe perennial asthma, we investigated cockroach asthma as a model. Twenty-eight subjects with bronchial asthma due to cockroach hypersensitivity (BACR) were divided into two groups in alternating order: 15 were started with cockroach antigen immunotherapy (CRa-IT) and 13 were given control immunotherapy. Eleven in the former group and two in the latter group completed the study after 5 years. The changes in symptoms and medication scores were assessed; blocking antibody factor in the paired pre- and postimmune serum of the two groups was measured and compared. Cellular sensitivity (HR50) was measured using the basophil-rich leukocytes (BRLs) obtained from the two treated asthma groups, and the result was compared with that of the untreated cockroach asthmatic cells. The average symptom score changed from 7.2 +/- 2.7 to 1.2 +/- 0.4 in the CRa-IT group. The control-IT group showed no change. The medication score changed from 11.4 +/- 1.6 to 5.2 +/- 1.4 in the CRa-IT group only (p less than 0.01). The mean blocking antibody factor in the immune serum of the CRa-IT group showed a 2.5 x 10(2)-fold increase [1.3 +/- 0.3 x 10(-1) in postimmune serum/5.2 +/- 2.0 +/- 10(-4) in preimmune serum (p less than 0.001)]. No difference was noted in the HR50 of the BRLs in the post- and preimmune serum of the control-IT group. Antihuman IgG absorption of the post-CRa-IT serum reduced the blocking antibody to 1/1000-fold; no difference in the HR50 of the BRLs was noted between the post-control-IT and the pre-CRa-IT serum (p greater than 0.2). The BRLs of the CRa-IT asthmatics, however, showed blunted sensitivity not affected by the serum factor (5.8 +/- 1.5 x 10(-2) micrograms/ml in post-CRa-IT serum and 5.6 +/- 1.3 x 10(-2) micrograms/ml in pre-CRa-IT serum) (p greater than 0.2). The BRLs of the control-IT group retained their cell sensitivity as well as the blocking effect of the CRa-immune serum. This study thus demonstrated that CRa-IT reduces symptom and medication scores clinically in cockroach-asthmatic subjects, and the CRa-IT produces the CRa-specific blocking antibody of the IgG type. It also reduces anaphylactic leukocyte sensitivity, which is not affected by humoral factor.