ABSTRACT
Innate part of the human immune system tackles bacteria or foreign particle entry to the human body. As integral components, monocytes, and neutrophil granulocytes circulate in the bloodstream and readily eliminate pathogens or clear particles (Roslavtseva and Ivanova, 1975; Schwarzer et al., 1999). Monocytes are the parent cells for more stable and/or long lived macrophages or dendritic cells, which represent integral part of innate immune defense mechanism (Auffray et al., 2009). Macrophages are white blood cells that are mainly produced in bone marrow. Their primary function is immunity against bacteria and other pathogens. Macrophages also help the body to clean up cellular debris from organs through phagocytosis. They can act by a number of different mechanisms: directly, by destroying bacteria and pathogens’ antimicrobial proteins, reactive oxygen species, and proteolytic enzymes (Cohen, 1994); indirectly by inducing certain pro-inflammatory cytokines [interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and nitric oxide synthase-2 (NOS2)] (Kanwar et al., 2009; Vadiveloo, 1999) which can activate other immune cells; and by repairing tissue damage (Vadiveloo, 1999). Macrophages originate in the bone marrow and are transported around the body via blood circulation. They can be differentiated after being modified with cytokines and resides in specific organs as a form of specific defense mechanism (Xaus et al., 2001). When they are required for inflammatory responses, macrophages need to be activated and become fully functional by interaction with the cytokine interferon-gamma (IF-γ), as well as its own growth factor macrophage colony-stimulating factor (M-CSF) (Mosser, 2003). Once they interact with these molecules they can either proliferate, become activated, differentiate into their stationary phases or die through apoptosis, if not needed. However, once they have been activated by M-CSF, proliferation is inhibited with further contact of IF-γ as well as the protein lipopolysaccharide (LPS) to be able to carry out their given functions (Vadiveloo, 1999). It was previously mentioned that macrophages indirectly induce this cytokine to activate other immune cells. Furthermore, there is conflicting data saying that instead of the growth factor M-CSF being a key role in activation, the other signal comes from TNF (Bastus et al., 2009a, 2009b). It can be concluded from the above observations that macrophage activation induces the different cytokines and their proliferation subsequently inhibited. In addition to the above mentioned phagocytic mechanisms, neutrophil granulocytes release structures into the extracellular space that mainly consist of DNA and protein and trap pathogens at infection sites
(neutrophil extracellular traps (NETs) (Brinkmann et al., 2004). These structures contain a variety of antibacterial proteins from azurophilic granules. Recent reports have shown that the formation of extracellular traps is not restricted to neutrophils but they are formed as well by mast cells for entrapping pathogens (von Kockritz-Blickwede et al., 2008).
