Modulation of bacterial DNA binding to human neutrophils

FUXMAN BASS, JUAN IGNACIO; ALVAREZ MARÍA EUGENIA; GEFFNER, JORGE RAÚL; VERMEULEN, MÓNICA; SALAMONE, GABRIELA; TREVANI, ANALÍA SILVINA

Córdoba, Argentina

Congreso; VII Congreso Latinoamericano de Inmunología; 2005

Asociación Latinoamericana de Inmunología

We have previously demonstrated that bacterial DNA induces human neutrophil activation by a TLR9- and CpG-independent mechanism. Bacterial DNA recognition is mediated by a receptor expressed on neutrophil surface. In this study we determined conditions that modulate bacterial DNA binding to neutrophils. Binding was evaluated with biotinylated-E coli DNA and FITC-avidin. Results indicated that methylation of bacterial DNA did not modify its binding capacity (n=5). Binding was not influenced by the presence of calcium, magnesium or EDTA (n=6) neither by the presence or absence of serum (n=6), in agreement with our previous results indicating these factors are not required for neutrophil activation by bacterial DNA. Additional results indicated that DNA binding was markedly increased after neutrophil stimulation with IL-8 (5 nM), FMLP (10-7 M), PMA (20 ng/ml) or after cross-linking of Fcg Receptor II (n=5, p<0,05), suggesting that the receptor could be translocated to the plasma membrane from intracellular stores. However, our results do not exclude that under these conditions the activation of an endogenous sialidase could be responsible for the enhancement in DNA binding capacity, since neutrophil treatment with Vibrio cholerae neuraminidase significantly increased bacterial DNA binding (n=5, p<0,05). Since neutrophils transmigrated across HUVEC monolayers in response to IL-8 also exhibited an increased DNA binding capacity (n=2), our results suggest that bacterial DNA recognition by neutrophils might be increased at inflammatory foci.