Study of Blood Samples and Risk of Infection in Patients With Newly Diagnosed Malignant Supratentorial Astrocytoma

DISEASE CHARACTERISTICS: * Histologically confirmed primary malignant brain tumor in 1 of the following groups: * High grade (grade III or IV) supratentorial glioma receiving antineoplastic treatment and with 1 of the following histologies: * Anaplastic astrocytoma * Glioblastoma multiforme (giant cell glioblastoma or gliosarcoma) * Anaplastic oligodendroma * Low grade (grade I or II) supratentorial glioma not planning to receive treatment of any kind (including steroids) and with 1 of the following histologies: * Astrocytoma * Oligodendroglioma PATIENT CHARACTERISTICS: * Karnofsky performance status 60-100% * No HIV positivity PRIOR CONCURRENT THERAPY: * No prior chemotherapy for brain tumor except polifeprosan 20 with carmustine implant (Gliadel® wafer) * No prior cranial radiotherapy or radiotherapy for brain tumor * No prior immunotherapy or biologic agents for brain tumor, including any of the following: * Immunotoxins * Immunoconjugates * Peptide receptor antagonists * Interleukins * Interferons * Tumor-infiltrating lymphocytes * Lymphokine-activated killer cell therapy * Gene therapy * Antisense therapy * No prior hormonal therapy for brain tumor * More than 14 days since prior and no concurrent steroid therapy for patients with low-grade (grade I or II) astrocytoma * Prior glucocorticoid therapy allowed