BCG-induced anaemia in mice: no direct effect of the growth of bacilli.

Mice receiving viable BCG intravenously (i. v.) rapidly and transiently develop anaemia, the origin of which is a decrease in erythropoietic progenitor cells. BCG-induced anaemia appears to be related to conditions which allow the development of a protective immune response against BCG infection. An increased number of blood phagocytes is strictly associated with the development of the anaemia and is dependent on the presence of T lymphocytes. Anaemia does not occur in some strains of mice: C3H/He Past strain was chosen as a typical non-responding strain and the opposite C57BL/6 strain as a responding one. Enumerations of BCG particles were performed in haemopoietic tissues, spleen and bone marrow of mice of the two strains in order to appreciate an eventual direct effect of bacilli growth on erythropoiesis. We never observed the particular growth of bacilli in mice which developed anaemia. On the contrary, the number of BCG viable units decreased progressively in responding strain C57BL/6 when numerations were performed after the 2nd month of the infection. This ability of C57BL/6 mice to control the infection contrasted with a relapse of bacilli growth in C3H.