## 3 Comparable Innate Immunity  
The insect immune system shares a high degree of structural and functional homology to the mammalian innate immune system, suggesting a shared ancestral precursor [35; 33]. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Feature**} & \multicolumn{1}{c}{**Small Animal Model (e.g.,**} & \multicolumn{1}{c}{**G. mellonella**} & \multicolumn{1}{c}{**Other Invertebrate Models**} \\ \multicolumn{1}{c}{} & \multicolumn{1}{c}{**Murine**} & & \\ \hline Innate immune system & & & \\ \hline Genome sequenced & & & \\ \hline Fast data production time & & & \\ \hline Standardised protocols & & & \\ \hline Facilitates reduction of animal testing & & & \\ \hline Adaptive immune system & & & \\ \hline Inexpensive (comparatively) & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Advantages and disadvantages of _Galeria mellonella_ as in vivo model for research activities compared to the small animal model and other invertebrate in vivo models (e.g., _Caenorhabditis elegans_ (_C. elegans_), _Drosophila melanogaster_ fruit fly, and zebrafish (_Danio rerio_). Once the physical barriers of the mammalian or larval host are breached, innate immunity mechanisms are triggered by first recognising \"non-self\" structurally conserved molecules on the microbe surface, called pathogen-associated molecular patterns (PAMPS), using pathogen recognition receptors (PRRs), before mounting a response. Indeed, the Toll-signalling pathway first identified in the fruit fly _Drosophila melanogaster_ led to the Nobel prize-winning discovery of the family of human PRR called Toll-like receptors (TLR) which resembles the human interleukin-1 (IL-1) signalling pathway [36]. When the cellular PRR recognise and bind to the PAMP, one of three signalling pathways (Toll, IMD, and JAK/STAT) are activated, resulting in the induction of host immune responses mediated via transcriptional control of specific immune-related genes (e.g., antimicrobial peptides and opsonins) [37]. These insect signal transduction pathways are analogous to mammalian pathways with both sharing the same molecular transducers, such as MyD88, and its downstream NF-kB master immune transcription factor [33]. Similar to its mammalian counterpart, the _G. mellonella_ innate immunity consists of both cellular and humoral (soluble factors) components. The cellular immune system of insects is mediated by a family of phagocytic cells called haemocytes, which patrol the larvae's blood (haemolymph) or remain associated with the internal organs and body fat. There are several haemocyte sub-types, but plasmatocytes, granulocytes and oenocytosis have been shown to have a clearly defined role in larvae immune responses [34; 35; 38; 39]. Phagocytosis is a process where certain immune cells (phagocytes) recognise \"non-self\" PAMPs via cell surface expressed PRR leading to the internalisation of the foreign pathogen, and its subsequent destruction by a combination of lysosomal enzymatic degradation and reactive oxygen species (ROS). Haemocytes (principally, plasmacytes and granulocytes) express mammalian-like PRR, such as apolipoprotein III (apoLp-III) [40; 41] and calreticlin [42], which are crucial to produce ROS and the enhancement of engulfed pathogen lysozymal degradation [43]. Other PRR human homologues identified in _G. mellonella_ are lepidopterans, haemoglobin, peptidoglycan rotegin (PGRPs), \(\beta\)-1,3-glucan recognition proteins (\(\beta\)GRPs), Gram-negative bacteria binding proteins (GNBs), and C-type lectins [37]. Furthermore, like mammalian macrophages and neutrophils, haemocytes possess the machinery essential for phagocytosis (pseudopodia) and subsequent pathogen destruction (lysosomes and NADPH oxidase system) [35]. For example, the _G. mellonella_ haemocyte in vitro phagocytosis activity upon bacterial infection has been shown to increase over the first hour post-infection and then plateau after about 2 h [44]. The same study showed that haemocytes are twice as efficient at engulfing Gram-negative bacteria (_E.