An analysis of the role of lymphatic leukemia virus in the immunodepression exerted by Friend complex in leukaemia-resistant C57BL/6 mice.

Leukaemia-resistant C57BL/6 mice inoculated with the Friend complex (FLC) present a transient but definite depression of the ability to develop IgM and IgG antibody-producing cells to sheep red cells (SRC). In this paper it is shown that this immunodepression cannot be attributed solely to the lymphatic leukaemia virus (LLV) component of FLC which is immunodepressive in susceptible mice. This conclusion was reached by investigating the immunological reactivity of C57BL/6 mice following inoculation with two isolates of LLV. Circumstantial evidence obtained by examining the replication of FLC and LLV, the antibody response to E. coli lipopolysaccharide (LPS) and the ability of syngeneic macrophages administered together with the antigen to restore the response to SRC points to the same conclusion. There were also indications that the low sensitivity to depression by viruses of the Friend complex exhibited by the anti-LPS antibody response is due to the mitogenic activity of this antigen.