Spontaneous immunity to mammary-tumour virus (MTV)-associated antigens in mice and its influence on syngeneic mammary-tumour growth

Abstract

Peritoneal cells from mice untreated but naturally infected with MTV (CBA/Bln mice and (XVII ♀ × CBA ♂) F 1 -hybrids) showed inhibited migration when incubated with MTV-containing tumour preparations. Incubation of those cells with MTV-free tumour or tissue preparations had no influence on the migration. Peritoneal cells from MTV-free XVII/Bln mice were inhibited neither by MTV-containing tumour preparations nor by MTV-free materials. These findings may indicate that mice naturally infected with MTV can develop some degree of cell-bound immunity to MTV-associated antigens without any further antigenic stimulation. This phenomenon is in line with the previous detection of serum antibodies to MTV in untreated but infected mice of several strains. Three grafted mammary tumours sharing MTV-associated antigenicity grew faster in syngeneic CBA mice with spontaneous antibodies to MTV than in mice without detectable antibodies. On the contrary, the results of macrophage migration inhibition tests obtained for every single host before tumour challenge did by no means correlate with the tumour growth. The possibility is discussed that spontaneously occurring antibodies to MTV may facilitate mammary tumour growth. The missing correlation between MTV-dependent macrophage migration inhibition and tumour growth may be due partially, at least, to an interference of the spontaneous humoral response to MTV-associated antigens with the cell-bound one.