Processing of mycobacterial antigens by immunoproteasome is necessary to control infection and to protect the organism from the development of active tuberculosis. We have investigated the activation of transcription of immunoproteasome subunit genes in peritoneal monocytes of C57Bl/6 mice infected with a vaccine M. bovis strain BCG and a virulent M. tuberculosis strain H37Rv. The level of transcription of LMP2, LMP7, and MECL1 subunits did not increase on the first and second days after a single infection. After two rounds of infection with M. bovis BCG, only the transcription of the LMP7 subunit gene was enhanced. However, the subsequent infection of monocytes, first with the vaccine strain, then with the virulent strain, resulted in a dramatic rise in the transcription of all immunoproteasome subunit genes. The transcription of the gene that encodes the PA28α subunit of the PA28 regulatory complex was activated only after a single infection of monocytes with M. bovis BCG. Thus, vaccination with M. bovis BCG promotes the efficient activation of immunoproteasomal genes in the case of subsequent contact with the virulent M. tuberculosis strain H37Rv.