Nonspecific and specific immuno-suppression in tumour-bearing mice by soluble immune complexes

SEVERAL reports have concerned themselves with specific suppression (blocking) of tumour-immune responses by serum factors from tumour-bearing animals^1-3, and nonspecific depression of T lymphocyte responses in tumour-bearing mice has also been described^4,5. Evidence exists that specific blocking of lymphocyte-mediated immunity occurs by means of either free antigen⁶ or antigen-antibody complexes⁷. It has now been suggested that nonspecific suppression of lymphocyte responses could also occur by means of immune complexes⁸, if one assumes that both T and B lymphocytes have F_c receptors for the antibody region of such complexes. There is a growing body of evidence for F_c receptors of T cells^9,10. We have investigated the possibility that the nonspecific depression of the T lymphocyte phytohaemagglutinin (PHA) response seen in BALB/c mice carrying tumours, induced by Moloney sarcoma virus (MSV) in the progressive phase of growth⁴, is caused by similar factors to those which cause specific blocking in this system. Our results suggest that while tumour-specific blocking can be mediated by free antigen, as well as antigen-antibody complexes, nonspecific blocking of T-cell responses is mediated only by the latter.