Estrogens are effective means of treating advanced prostate cancer. In randomized studies estrogens have better cancer control rates than orchiectomy alone, suggesting that estrogen efficacy is not limited to its ability to suppress testosterone. One hypothesis is that estrogens modulate immunity to prostate cancer through direct activation of effector cells and by upregulating cytokines in prostatic stroma. Administration of estrogen in murine models induces infiltration of normal prostate with T lymphocytes even in castrate male animals potentially through induction of autoimmunity to normally cryptic prostate antigens. Estrogens activate multiple immune effectors and autoimmunity in a broad variety of experimental settings, suggesting upregulation of immune recognition on many levels. Pilot data demonstrates that estrogens upregulate expression of interferon regulated genes, major histocompatibility antigens (MHC) on prostate cancer, and increase both number and activation of natural killer (NK) cells. Other groups have shown that standard forms of androgen deprivation also induce immunity against both normal and malignant prostate tissue. We propose to test the hypothesis that administration of estrogen and/or androgen deprivation induces immune recognition of prostate cancer in humans through upregulation of major histocompatibility antigens on tumor and induction of tumor specific immunity. The specificity of estrogen effect will be tested by comparing measures of immunity in patients treated with estradiol, androgen deprivation or no neoadjuvant therapy.