An important step in prostate cancer development is tumour immune escape manifested among others in defects in antigen presentation (human leukocyte antigen (HLA) class I receptor deficiency on cytotoxic T cells), imbalance in T helper type 1 (Th1) and Th2 cytokine production leading to elevated levels of immunosuppressive cytokines such as interleukine-4 (IL-4), IL-6 and IL-10. This evidence concerns the gene IL4 and Familial prostate cancer.