Malignant changes in New Zealand black mice.

Ageing, Coombs positive, NZB mice, may spontaneously develop a neoplasia of the reticulum cell type which can be transferred by serial passage of their lymphoid tissues in young intact or neonatally thymectomized syngeneic recipients. The recipients (103/117) of cell suspensions prepared from the enlarged spleens and/or lymph nodes of four such donors developed an extensive and lethal reticulum cell neoplasia affecting the spleen, lymph nodes, lungs and liver but the bone marrow, thymus and kidneys were seldom involved. The recipients (16/17) of spleen cells from a fifth donor showed massive proliferations of eosinophils in all the organs examined. Prematurely positive antiglobulin (Coombs) reactions were detected in only two recipients. Although there was an indication that the IgM content of the sera decreased as one of the passages progressed, the levels of IgG and IgA were not seriously distorted. Particles resembling murine leukaemia virus were identified by electron microscopy in the spleen and in plasma or serum pellets of passage recipients. However, similar particles were also seen in the thymus and/or spleen or bone marrow of untreated NZB mice including an 18-day embryo and animals aged 1–56 weeks, although no particles were found in plasma and serum pellets of mice aged 6–70 weeks. The theory that autoimmunity, malignancy and virus infection are directly related is discussed.