Membrane surface of Mycobacterium microti-infected macrophages antigenically differs from that of uninfected macrophages

Identification of the antigenic changes in mycobacteria-infected macrophage may be important in understanding the mechanisms responsible for the intra cellular survival of the bacteria. In the present study, Mycobacterium micr oti-infected macrophages were utilized to investigate the possibility of di fferentiating the infected cells from normal cells, based on the antigenic changes occurring in the membranes. Antisera were generated against bacteri al extract, heat-killed bacteria and crude preparation of M. microti-infect ed homologous macrophage membrane. The reactivity of these antisera, toward s in vitro infected macrophages, was compared by flow cytometry. Unlike ant i-bacterial extract antiserum or anti-heat-killed bacterial antiserum, anti -infected macrophage membrane antiserum reacted with infected macrophage su rface. This reactivity increased with the increase in post-infection time. However, it was not observed with uninfected macrophages, PMA- or lipopolys accharide-activated macrophages and those harboring Mycobacterium tuberculo sis H37Ra, heat-killed M. microti and Leishmania donovani. Interestingly, a nti-infected macrophage membrane antiserum identified a 63-kDa antigen in M . microti-infected macrophage membranes which was not present in the membra nes of normal macrophages, activated macrophages and of those infected with M. tuberculosis H37Ra, heat-killed M. microti and L. donovani. Thus, membr anes of M. microti-infected macrophages differ antigenically from those of the normal macrophages and infected homologous macrophage membrane antiseru m provides a useful tool in studying such changes. (C) 2000 Federation of E uropean Microbiological Societies. Published by Elsevier Science B.V. All r ights reserved.