Background and Aim: Immune cells play a prominent role in inflammation and cancer. In these conditions these cells encounter with metabolic stress. In this study we investigated the effect of serum starvation stressor on human PBMCs. Material and Methods: PBMCs were isolated by Ficoll-Paque from three persons aged 20 30 years. The cells were cultured in glucose containing serum-free RPMI-1640 for 16, 48,72, and 96 hrs as well as in complete medium supplemented with 10% fetal bovine serum FBS . After indicated time, the cell culture supernatants were harvested and the cell counts were obtained by Neubauer chamber and then all starved cells re-feed with serum for 72hrs. Total protein concentrations were measured by Bradford method in cell culture supernatants and then the relative molecular weight of proteins was obtained by SDS- PAGE. To explore of immunomodulatory effects of these proteins, the pooled cell culture supernatants were separately prepared from the 16hrs- and 96hrs starved cell culture supernatants. These pooled supernatants were incubated for 96hrs with three fresh PBMCs prepared from three subjects aged 20-30 years in standard cell culture system. Then the cell counts and viability were obtained by Neubauer chamber and trypan blue dye exclusion test and then MTT proliferation assay was performed. Therefore, affected separately prepared from the 16hrs- and 96hrs starved cell culture supernatants with breast cancer stemcell LA7 rat and viability were obtained by MTT proliferation assay was performedResults: In comparison to non-starved control cells, the cell count was significantly decreased in all starved groups especially in 96hrs starved group except 16hrs starved P<0.0001 . The count of 16-h starved group was not significantly changed. Surprisingly after re-feeding, 96hrs- and 16hrs serum-starved PBMCs showed the highest and lowest proliferation rate, respectively P < 0.05 . Remarkable level of total protein was detected in all starved
PBMCs culture supernatants which reached highest level in 96hrs starved cells group. These proteins had relative molecular weight of 7.5-147kDa.There was no significant difference in cell count between the fresh cells which were cultured in 96hrs starved cell culture supernatants and control cells. However, count of the fresh cell cultured in 16hrs starved supernatant significantly decreased compared to control cells P<0.05 . also, proliferation of the LA7 with 16hrs starved supernatant treated significantly decreased compared to LA7 with 96 hrs starved supernatant treated. P<0.05 Conclusion: These results indicate that in response to serum starvation cellular stressor, human PBMCs produce proteins which some of them support the immune cells survival whereas some other kills them. Thus, these proteins can be considered as immunomodulatory tool.