Pathogenic Bacteria

Humans and bacteria have a unique relationship, which has both positive and negative outcomes on human beings. In fact, the human body’s surfaces are inhabited by numerous bacteria, known as normal flora (Hornef et al., 2002). These normal flora may act as commensals or be mutualistic, which means that they are either harmless or beneficial microorganisms (Cogen et al., 2008). However, serious invasive diseases, such as meningitis and septicemia are caused by several pathogenic bacteria (Hornef et al., 2002). The occurrence of such diseases requires unique strategies, which assist bacteria to survive inside the host and evade their immune response (Akira et al., 2006). Several pathogenic bacteria have developed efficient capabilities to counteract …show more content…
It includes Mucus membrane, secretory immunoglobulin A (sIgA), macrophages and antigen presenting cells (APCs). A good example of primary innate immune defense is the mucus membrane, which eliminates bacterial adhesion by ciliary movement or mucus in the upper respiratory tract (Fedtke et al., 2004). Bordetella pertussis is a well-known example of the strategy that disables the clearance role of ciliary epithelial cells in the upper respiratory tract. This bacterium releases tracheal cytotoxin, which impairs ciliary movement and leads to the colonization of the microorganism (Hornef et al., 2002). SIgA covers the mucus membrane, and it is part of the primary defenses. SIgA acts as an opsonizing factor that binds to any non-self-antigens like bacterial antigens to stimulate the immune system (Geme et al., 1994). Haemophilus influenzae type B is a good illustration of a unique subversion mechanism for sIgA. Haemophilus subverts these antibodies by releasing proteolytic degrading enzyme, which destroys sIgA (Geme et al., 1994). Thus, the former examples demonstrate some pathogens’ approach to circumvent the primary …show more content…
The following is a brief review for some evasion mechanisms of adaptive immunity. T cells and B cells are the main components of the adaptive immunity. Besides their abilities to produce a diversity of antibodies against pathogens, they develop memory cells that can remember pathogens antigens (Medzhitov, 2007). Some pathogenic bacteria intervene with T and B cells receptors in order to avoid these cells (Hornef et al., 2002). Yersinia pseudotuberculosis is a good illustration of this mechanism. Yersinia outer membrane protein H (YopH) produces tyrosine phosphatase protein, which suppresses interleukin 2 (IL-2) synthesis by the T cell. Moreover, this protein inhibits the activation of T cell antigen- specific receptors. In addition, the B cell shows an incapacity for the up-regulation of the co-stimulatory molecules expression of CD86, in interaction with pathogen stimulation (Yao et al.,