HAEMOPOIETIC DEFECTS IN MICE INFECTED WITH LYMPHOCYTIC CHORIOMENINGITIS VIRUS

Abstract

In the preceding report (3) experiments were described which suggested the occurrence of haemopoietic disorders in mice infected with the LCM virus. Immunological disorders associated with the LCM virus infections of mice are well‐known. It was considered that both haemopoietic and immunological defects might be caused by some virus‐induced interference with the stem cells in the infected mice. Attempts were therefore made to estimate the numbers and the function of stem cells in mice infected with the LCM virus. Haemopoietic colony assays were employed, and both acutely infected mice and persistent, tolerant virus carriers were examined. The findings suggested a decrease in colony‐forming stem cells in the bone marrow during the acute infection. However, the most striking observation in the acutely infected mice was of a profound inhibition of the colony‐forming response of stem cells in these animals. The influences exerted upon the stem cell response seemed to be quite specific, in that the response of immunocompetent cells was almost unimpaired when examined at the same time. The inhibition was not caused by a direct viral effect upon the stem cells, nor by any immune‐mediated damage. Experiments with the adult, persistent, tolerant virus carriers indicated that the haemopoietic colony formation was not inhibited in these mice despite a pronounced viraemia. However, their numbers of colony‐forming stem cells amounted to about fifty per cent of the normal values and seemed to agree with their relative increase in sensitivity to X‐rays. It is suggested that virus‐induced interference with the function of haemopoietic stem cells plays a central role for the tolerogen effects of the LCM virus.