Any invading pathogen, like
Candida, faces a significant challenge from the host immune system. Pathogen recognition receptors (PRR) identify particular fungal pathogen-associated molecular patterns (PAMP), which include essential and specific fungal cell wall components such as glucan, chitin, and mannan (PRR). When fungi infect our bodies, the cell wall is crucial in triggering an immune response. The inner cell wall of fungi is high in glucan, which is responsible for triggering an inflammatory response, but immune cells are unable to recognize it. As soon as the -glucan is exposed, it is recognized by Dectin-1, a C-type lectin PRR
[7][8]. When Dectin-1 recognizes β-glucan, myeloid cell signaling is activated along with the phagocytic response, and a pro-inflammatory cytokine response is introduced. Other activities for destroying fungal cells by neutrophils and macrophages are also initiated via their reactive oxygen (RO) and reactive nitrogen (RN) species
[9][10]. Dectin-1 receptor shows an association with β-glucan, whereas the Dectin-2 receptor is associated with the α-mannan, which is found on the fungal cell’s outer covering
[7][9]. With the aid of macrophages, dendritic cells, and neutrophils, Dectin-1 receptors boost innate immunity against
Candida albicans [10][11]. Macrophages are essential in the detection of invading fungal cells. Si Min Chen et al. found that macrophages lacking Dectin-1 were unable to mount an effective response to
C. albicans stimulation
[12]. Ywp1 is one such component that helps the glucan particle remain masked and guards against immune cells’ identification
[13][14]. In deprivation of O-mannan from the fungal cell wall, β-glucan gets unmasked and eventually gets recognized by Dectin-1, resulting in expanded phagosome maturation
[15]. Nina Klippel and team showed that Chk1p is responsible for the masking of mutant β-glucan to prevent recognition by the immune cells
[16]. Dectin-1 triggers CR 3 and S1GN-R1 to generate signaling. Dectin-2 and -3, on the other hand, have a synergistic effect on inflammatory responses
[17]. Dectin-1 binds soluble β-glucan and particulate β-glucan, a ligand that is similar to β-glucan found in cell walls. In response to glucan-coated beads, dendritic cells (DCs) release reactive oxygen species (ROS). This response can be produced by glucan particles with a diameter of 500 nm or larger, but not by particles with a diameter of 200 nm or smaller. It indicates that glucan detection can be dependent on the physical properties of glucan at nanometric scales. However, the precise dimensions of β-glucan exposure necessary for Dectin-1 activity are still unknown. Since Dectin-1 signaling is ligand size-dependent, masked β-glucan exposures may be limited to non-stimulatory sizes, while unmasking processes may result in larger β-glucan exposures that are more effective at activating Dectin-1. This highly immunogenic molecular pattern is linked to dendritic cell, macrophage, and neutrophil activation, primarily by Dectin-1 and also by β2-integrin
[10]. PRRs help DCs and other leukocytes identify the polysaccharides found on fungal cell walls. Dectin-1 and the DCSIGN transmembrane C-type lectins (CTLs) are the proteins bound to β-glucan and mannan, respectively. Dectin-1 detects β-glucan, triggering an immunogenic response that leads to cellular activation in innate immune cells and fungal phagocytosis. When PRRs are activated, DCs enter the picture and take care of both innate and adaptive immunity by guarding pathogen entry. As a result, controlling the amount and exposure of immunogenic cell-wall ligand is an important feature of the host-pathogen relationship that requires further investigation.