CD80 COSTIMULATION IS ESSENTIAL FOR THE INDUCTION OF AIRWAY EOSINOPHILIA

CD80 and CD86 (B7-1 and B7-2) are the ligands on antigen-presenting ce lls (APCs) which bind CD28 and deliver the costimulatory signals neces sary for T cell activation. The reasons for the existence of two CD28 binding molecules are not well understood. We created a mutant version of CTLA4-Ig that could selectively bind CD80 and block CD28-CD80 inte raction but leave CD28-CD86 binding intact. CD80-blockade prevented an tigen-induced accumulation of eosinophils and lymphocytes ill the lung of immunized mice, but did not block antigen induced systemic blood e osinophilia or IgE antibody production. No preferential expression of CD80 could be demonstrated on a population of lung APC consisting main ly of macrophages. These results indicate that CD80 costimulation is n ot necessary for the induction of Th2 immune responses but rather for the maintenance or amplification of lung inflammatory responses.