Yersinia pseudotuberculosis derived-mitogen (YPM) increases levels of nitric oxide production from murine macrophage cell line RAW 264.7 and presents different effects on proliferation rates over naïve or LPS-activated macrophages.

BAUER A. B; .DE MARZI M; CHIAPPINI S A ; ROMASANTA P ; TODONE M; FERNÁNDEZ M. M; MALCHIODI E.L

Buenos Aires

Congreso; I Congreso Argentino –Francés de Inmunología y LVIII Reunión Anual de la SAI; 2010

Sociedad Argentina de Inmunología

Yersinia pseudotuberculosis (Y.p) has been suggested as one of the causative agents of Kawasaki syndrome, a vasculitis affecting predominantly infants and young children. Yersinia infection produces suppression of the host defense by interfering with macrophage phagocytosis and oxidative burst generation, which culminates with the induction of the intrinsic macrophage cell death program. Y.p has been identified as the only one gram-negative human pathogen which produces a superantigen (SAg) called YPM. Since SAgs are referred as immunesuppressor factors promoting the spread of bacterial infection, we analyzed the effect of YPM on macrophages.  For that purpose, we analyzed the effects of YPM over naïve and activated macrophages.exanimate the effects of YPM on the activation of RAW 264.7 macrophage cell line with LPS used as a positive control. We found that YPM was able to increase (P <0.05) the production of NO, as indicator of the activation, at 72h post stimulation. To determine if this was a characteristic of YPM, RAW cells were also treated with SEG and SEC-3 showing not production of NO.Naïve macrophages are the sources of macrophages that mounts an effective immune response suggesting YPM would be able to activate macrophages. In an attempt to elucidate if YPM could participate in one of these two processes, we study the effect of YPM over both naive RAW 264.7 and J774-A1 murine macrophage cell lines and over LPS-activated RAW 264.7 macrophages. Cells (1x106/ml) were incubated for 24 and 72h with YPM or SEG at concentration ranging from 0.05 μg/ml to 100 μg/ml . Treatments with both superantigens notably decrease (P <0.05) tritiated thymidine (3H-TdR) uptake from both naive RAW 264.7 and J774-A1 cells at all the times analyzed. In contrast, macrophages previously activated with LPS (30ng/ml) for 48h show no decrease of 3H-TdR uptake(P <0.05)(in comparision with basals) when treated with YPM (50 µg/ml) or SEG (100 µg/ml) for 24h. In conclusion, YPM activates RAW 264.7 cells and may participate in death of naïve cells by apoptosis in Y.p infection, although further analysis is required.Nitric oxide (NO) is a signaling molecule produced by activated macrophages which is important in defense against pathogens.