One of the major obstacles in tumor-immunology is the outgrowth of malignan
t tumors despite their immunogenicity and recognition by the immune-system.
Multiple mechanisms for this phenomenon have been proposed. We review the
possible involvement of transforming growth factor beta (TGF-beta) in this
context. TGF-beta is a cytokine with pleiotropic functions, involved in mul
tiple physiologic processes including immunoregulation. Immune elimination
of most cancers ultimately depends on cytolytic T cells (CTL). We propose a
mechanism of specific suppression of cytolytic T cell (CTL)-responses medi
ated through immunoglobulin-bound TGF-beta (IgG-TGF-beta), secreted by acti
vated B cells, and a cell of myeloid origin. This mononuclear "Veto" cell p
resumably binds IgG-TGF-beta through Fc-receptors and activates latent TGF-
beta. The suggestion that B cell responses can inhibit tumor rejection is s
upported by observations in B cell-deficient mice. Ways for enhancing effec
tive cancer immunity by interfering with the network of interactions involv
ing IgG-TGF-beta are discussed. Microsc. Res. Tech. 52:387-395, 2001. (C) 2
001 Wiley-Liss, Inc.