LIPIDS FROM MYCOBACTERIUM-LEPRAE CELL-WALL ARE ENDOWED WITH AN ANTIINFLAMMATORY PROPERTY AND INHIBIT MACROPHAGE FUNCTION IN-VIVO

In general, the majority of bacteria are pro-inflammatory when injecte d in experimental animals. However, Mycobacterium leprae has no inflam matory effect when injected into mouse footpad, but using the delipida ted mycobacteria we observed a mild significant increase in footpad oe dema. Other mycobacteria, Mycobacterium bovis-BCG or M. tuberculosis i nduce a strong paw oedema. Furthermore, M. leprae reduced locally the BCG-induced inflammatory reaction in mouse footpad, whereas delipidate d M. leprae did not influence this reaction. Both M. leprae and M. lep ,ae cell wall lipids blocked immune phagocytosis in vivo by inflammato ry macrophages (from an induced focus). In contrast delipidated M. lep rae stimulated the phagocytosis reaction. Neither intact M. leprae, de lipidated M. leprae, nor its lipids had any toxic effect on macrophage s or on cell migration. Although M. leprae did not interfere on cell i nflux and cell type in an induced-inflammatory site, this mycobacteriu m led to the appearance of a distinct cell population in vivo. The hyp othesis is that M. leprae would transform macrophages in epithelioid c ells, suggested by morphology analysis of cells by fluorescence-activa ted cell sorter and observed under optic microscopy.