Our Body's Immune System

3005 Words12 Pages
The body's innate immune response is non-specific and provides the first line of defense against invading pathogens such as bacteria through various receptors that detect bacterial components such as the Toll-like Receptors (TLRs). TLRs are a highly conserved family of proteins that play an important role in pathogen recognition and activation of innate immunity. They are transmembrane proteins that detect different components of a bacterial pathogen. Specifically, Toll-like Receptor 4 (TLR4) detects lipopolysaccharide (LPS) from gram-negative bacteria which leads to an activation cascade of cytoplasmic proteins and transcription factors. This results in the induction of cytokines and chemokines which lead to bacterial clearance by way of neutrophil recruitment. TLR4 uses adaptor proteins MyD88 and Trif to initiate the aforementioned signaling cascade. Despite being a receptor for LPS, TLR4 actually has a weak affinity for LPS while co-receptor CD14 has a strong affinity for LPS. However CD14 lacks a transmembrane domain so it cannot initiate cytoplasmic signaling to activate transcription factors for the induction of cytokines and chemokines. These differing characteristics of the LPS co-receptors necessitated the use of two types of knockout mice, one for each of the receptors. Neutrophil granulocytes, also known as neutrophils, belong to a category of white blood cells called polymorphonuclear leukocytes (PMN) due to the varying shapes of the nucleus, usually
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