PRIOR CONCURRENT THERAPY: Biologic therapy: No prior therapy with proteins of murine origin At least one month since prior immunotherapy No other concurrent immunotherapy Chemotherapy: See Disease Characteristics No concurrent chemotherapy Endocrine therapy: No concurrent chronic use of systemic corticosteroids Radiotherapy: See Disease Characteristics No concurrent radiotherapy including prophylactic cranial irradiation No prior spleen radiotherapy Surgery: No prior surgery for SCLC No prior splenectomy Other: No prior second-line therapy for SCLC At least one month since prior investigational agents No concurrent chronic use of systemic antihistamines or nonsteroidal anti-inflammatory drugs No concurrent immunosuppressive therapy