ABSTRACT
Carole Delmas, Anne Venisse, Alain Vercellone, Martine Gilleron, Renaud Albigot, Therese Brando, Michel Riviere, and Germain Puzo
National Center fo r Scientific Research, Toulouse, France
I. INTRODUCTION
Lipoarabinomannans (LAM) are ubiquitous components of the mycobacte rial cell walls [1]. According to their structures, LAM are classified in two types, namely, AraLAM and ManLAM. AraLAM were first isolated from an unidentified fast growing mycobacterial species [2], whereas ManLAM were found in slow growing strains such as Mycobacterium tuberculosis, Erdman strain [3,4], and in the Mycobacterium bovis BCG (Bacille Calmette-Guerin) [5,6] vaccine. The structural models of AraLAM and Man LAM reveal that they are composed of two homopolysaccharides, namely, the D-mannan and the D-arabinan (Fig. 1). The mannan is a linear oligo saccharide composed by 6-O-linked o:-D-Man/?s (mannopyranose) with side chains containing one single unit of a-D-Man/? attached at the position C2. At its reducing end, this mannan core is glycosylated by the phosphatidyl myo-Ins (inositol) anchor. Three major structural motifs composed the D-arabinan: (1) a linear oligosaccharide of 5-O-linked a-D-Ara/(arabinofuranose), (2) side chains attached via the C3, and finally, (3) terminal disaccharidic unit of /3-D-Ara/-(l -► 5)-a-D-Ara/ -► . The major struc tural difference between AraLAM and ManLAM is the presence of small mannooligosaccharide units capping the arabinan side chains of the Man LAM (Fig. 1). More recently, though, it was established that AraLAM from an unidentified fast growing mycobacterial species [2,7] and from Mycobacterium smegmatis (unpublished results) contain phosphoinositide caps. The AraLAM and ManLAM present a large spectrum of immunologi cal activities. Some of these activities are specific. For example, ManLAM bind murine and human macrophages via the mannose receptor [8,9] and activate human lymphocyte Ta/3 CD4 “ CD8 “ [10], whereas AraLAM stim ulate the precoce genes of the macrophage activation [11,12] as well as the
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Figure 1 Structural model of ManLAM and AraLAM.
