Anti-ManLAM antibodies circulating in Multi Drug Resistant (MDR) and Drug-sensitive tuberculosis (TB) patients exert differential effect on fagocytosis and costimulatory potential of Dendritic Cells.

SCHIERLOH, PABLO; ; COLMAN, ELIZABETH;; LANDONI, VERONICA; ; LABORDE, EVANGELINA; ; BASILE, JUAN; ; BALBOA, LUCIANA;; SABIO Y GARCÍA, CÁRMEN; ; ROMERO, MERCEDES ; GEFFNER, LAURA; ; BARRERA, LUCÍA; ; CASTAGNINO, JORGE;; SASIAIN, MARÍA

Congreso; Primer congreso Franco-Argentino de Inmunología; 2010

Mannosilated lipoarabinomannan (ManLAM) is an abundant cell wall glycolipid of pathogenic mycobacteria exerting its immunomodulatory effect through recognition by innate immune receptors of host cells. Anti-ManLAM antibodies (anti-ManLAM Abs) have been detected in serum from tuberculosis patients (TB) but its role in physiopathology remains unknown. To address the role of ManLAM Abs on dendritic cell (DC) function and factors/mechanisms involved, anti-ManLAM Abs were characterized in serum samples from 20 MDR and 20 Drug-sensitive TB patients and 17 healthy donors (N), thereafter, serum subgroups were employed to perform bioassays on monocytes derived DC from N. Immunochemical characterization showed heterogeneous anti-ManLAM response in terms of serum titers (ELISA), epitope chemistry (competition ELISA) and cell wall epitope-display (bacterial based ELISA) with no differences among patients, but above N (p<0.01). Isotypic analysis of anti-ManLAM Abs were performed by FACS on M.tuberculosis 6006 local strain (Mtb-6006) opsonized with pre-absorbed serum on plate bound ManLAM (anti-ManLAM depleted) and staining with antihuman-IgA, -IgE, -IgG and -IgM 2º Abs. Although isotypes showed high variability, IgG and IgM αManLAM Abs were inversely correlated between individuals (r=-0.39; p<0.05). FITC-conjugated bacteria (Mtb-6006-FITC) opsonized with total or αManLAM Abs depleted sera were used in DC mediated fagocytosis. Anti-ManLAM depletion inhibited fagocytosis in those sera with high IgG/IgM ratio, but in low IgG/IgM sera fagocytosis was favored or not affect. Finally, CD86/CD83 (stimulatory) vs PD-L1/PD-L2 (inhibitory) molecules were evaluated on DC matured with Mtb-6006 opsonized with total or ManLAM depleted sera. A strong increase in PD-L1/PD-L2 expression was observed by serum pretreatment only in those sera with high IgG/IgM ratio (p<0.01), whereas CD86/CD83 remain unaffected. Taken together, this data suggest an isotype dependent mechanism, presumably mediated by Fc receptors.