Theoretically, autologous prostate cancer cells may be the best source of prostate cancer antigens for eliciting therapeutically useful immune responses. However, evidence has accumulated to suggest that allogeneic prostatic carcinoma cells might also serve as useful sources of prostate cancer antigens for prostate cancer vaccine construction. One theoretical concern about the use of allogeneic prostate cancer cells to prime antigen specific T-cell immunity is whether cytolytic T lymphocytes (CTLs) restricted to the HLA molecules of the patient's tumors can be primed by vaccine cells expressing different (allogeneic) HLA molecules. Recent work has shown that the GM-CSF gene transduced tumor cells do not directly prime MHC class I restricted CTLs but are broken down by the recipient's antigen-presenting cells, which process and present these antigens on their HLA molecules to prime T cells. In fact, tumor cells that do not express any MHC class I molecules are nevertheless capable of generating systemic antitumor immunity that is comparable to their MHC class I positive counterparts.