Reaction of peripheral‐blood lymphocytes to the human chorionic gonadotropin β sub‐unit in patients with productive tumors

Human chorionic gonadotropin (hCG) and its β sub‐unit (hCGβ) are secreted by trophoblast cells during pregnancy, and by tumoral cells of trophoblastic and non‐trophoblastic origin. In contrast to hCG, the free hCGβ sub‐unit is consistently undetectable in healthy non‐pregnant subjects. With this in mind, we sought to determine whether an immune response to hCGβ can be detected in patients with bladder or germ‐cell testis cancers. Peripheral‐blood mononuclear cells (PBMC) from 31% of patients with hCGβ‐productive bladder cancers and 33% of testis‐tumor‐bearing patients displayed an hCGβ‐specific proliferative response, whereas no patients with non‐hCGβ‐productive cancers had a proliferative response. PBMC from pregnant women and healthy controls did not elicit significant reactivity. By the use of overlapping synthetic peptides, the immunogenic regions of hCGβ were delineated within the central 20–65 portion. Moreover, in 2 bladder‐cancer patients with the HLA DR7, DQ2 haplotype, the T‐cell response to hCGβ was focused on the hCGβ(20–47) peptide. Taken together, these results indicate that hCGβ is a tumor‐associated antigen capable of inducing a cell‐mediated immune response in patients with productive tumors. © 1995 Wiley‐Liss, Inc.