[Correlation between the production of mature mammary tumour virus particles and the histomorphological differentiation of murine mammary tumours].

The mammary tumour virus (MTV) contents of mammary tumours (MT's) of various mouse strains were investigated by means of the indirect immunofluorescence technique and the electron microscopy. Only in acinus-forming, well differentiated MT's MTV-B particles could be observed in high quantity. The release of B particles seems to be correlated with the degree of structural ripeness of the tumor tissue. As to intracytoplasmic A particles such a strong relationship could not be found out. Many A particles were seen in mature adenocarcinomas as well as in acinus-free tumours. Some mammary carcinomas of an extreme low degree of histomorphological differentiation were free of any detectable virus production. The indirect immunofluorescence test was confirmed as a sensitive method for the detection of MTV antigens in MT slices. Using polyvalent anti-MTV sera, obtained after immunization of rabbits with ether-disrupted B particles from tumour tissue or milk, the test system allowed the distinction of A and B particle antigens. Accumulations of B particles were seen as an intercellular fluorescence reaction while clusters of A particles were represented by a granular paranuclear reaction within the tumor cells.