Increase of tuberculous infection in the organs of B cell‐deficient mice

Protective immunity against infection with Mycobacterium tuberculosis is imparted by T cells rather than antibodies, but B cells can play a role as antigen‐presenting cells and in granuloma formation. We re‐evaluated the role of B cells in the course of tuberculous infection in μ‐chain knock‐out (Ig−) mice. Surprisingly, the organs of M. tuberculosis‐infected Ig− mice were found to have three‐to eight‐fold elevated counts of viable bacilli compared with normal littermates at 3–6 weeks post‐infection. Splenic interferon‐gamma responses to whole antigen were unimpaired, whilst proliferation to certain mycobacterial peptides was found to be diminished. However, bacille Calmette–Guérin (BCG) vaccination significantly reduced the infection in Ig− mice. The mechanisms by which B cells can influence primary tuberculous infection need further study.