Functional analysis of peptidoglycan recognition proteins (PGRPs). Effects on monocytes activation and bacteria clearence

TODONE M; DE MARZI M; FERNÁNDEZ MM; MALCHIODI E

Buenos Aires

Congreso; First French Argentine Immunology Congress; 2010

Sociedad Argentina de Inmunología-French Society of Immunology

PGRPs are PAMPs that bind or hydrolyze Peptidoglycan (PGN). We previously detected the presence of PGRP-S in serum and PMN and we do not observed bactericidal or bacteriostatic effect of PGRPs. PGRPs are PAMPs that bind or hydrolyze Peptidoglycan (PGN). We previously detected the presence of PGRP-S in serum and PMN and we do not observed bactericidal or bacteriostatic effect of PGRPs. With the aim to study the role of PGRPs in innate immune response, we produced human recombinant PGRPs to analyze their binding to monocytes surface and the effect on phagocytosis and proliferation. To study whether PGRPs would act as a link between PGN recognition and intracellular signaling we analyzed the binding of PGRPs-FITC to monocytes by flow citometry (FC). We observed an increase of positive cells from 1.4+0.1 to 2.0+0.2 times for different PGRPs at 4ºC that disappear after Tripan Blue treatment; and a higher increased (2.3+0.1 to 5.1+0.3 times) when incubated cells at 37°C that still remain positive after Tripan Blue treatment, indicating that binding and endocytosis events were occurring, respectively. To analyze the effect of PGRP on phagocytosis, we incubated monocytes with death S. aureus-FITC treated with PGRPs. A higher number of cells (2.8-3.0 times) phagocytate PGRP treated bacteria than bacteria without PGRP. On the other way, PGRP-S treatment of live S. aureus increased the uptake of bacteria by monocytes (105 UFC/ml), compared with PGRP-Ialfa, PGRP-Ibeta and controls (104 UFC/ml). By 72 h of incubation, surviving bacteria were only detected inside control cells, while PGRPs treated bacteria were killed. To determine the effect of PGRPs over monocytes proliferation, these cells were incubated with PGN treated with PGRPs. PGRPs reduce the inhibition of proliferation of monocytes produced by PGN, in a concentration dependent form, compare to controls with PGN only. Our results suggest that PGRPs are recognized by monocytes surface receptor increasing phagocytosis and blocking PGN effects.