Immune Cell Degranulation in Fungal Host Defence

Abstract

Humans have developed complex immune systems that defend against invading microbes, including fungal pathogens. Many highly specialized cells of the immune system share the ability to store antimicrobial compounds in membrane bound organelles that can be immediately deployed to eradicate or inhibit growth of invading pathogens. These membrane-bound organelles consist of secretory vesicles or granules, which move to the surface of the cell, where they fuse with the plasma membrane to release their contents in the process of degranulation. Lymphocytes, macrophages, neutrophils, mast cells, eosinophils, and basophils all degranulate in fungal host defence. While anti-microbial secretory vesicles are shared among different immune cell types, information about each cell type has emerged independently leading to an uncoordinated and confusing classification of granules and incomplete description of the mechanism by which they are deployed. While there are important differences, there are many similarities in granule morphology, granule content, stimulus for degranulation, granule trafficking, and release of granules against fungal pathogens. In this review, we describe the similarities and differences in an attempt to translate knowledge from one immune cell to another that may facilitate further studies in the context of fungal host defence.

Effects of dietary supplement with a Chinese herbal mixture on growth performance, antioxidant capacity, and gut microbiota in weaned pigs

“…White blood cells participate in the immune response of animals, and their abnormal increase indicates the presence of inflammation, so they are important clinical indicators for health status ( 65 , 66 ). Both neutrophils and monocytes are immune-related white blood cells that aid in the host's defense against invading pathogens ( 67 ). We next further investigated the effect of adding herbal medicine mixture to the diet on the immune index of weaned pigs.…”

T cell responses to control fungal infection in an immunological memory lens

“…Activated neutrophils and macrophages may exert direct fungicidal activity via phagocytosis, degranulation, ROS production, and neutrophil extracellular trap (NET) formation ( 203 ). Different granules (primary azurophilic, secondary specific, and tertiary gelatinase) in neutrophils contain different cytolytic molecules ( 17 ). The role of the IL-17 axis and neutrophils during dimorphic fungal infections has been reviewed elsewhere ( 204 ).…”

“…Despite the need for CD4 + T-cell help for CD8 + T-cell activation and memory maintenance in viral and bacterial infection scenarios, using mouse models of fungal infections against Pneumocystis , Histoplasma , and Blastomyces , the studies have shown that antifungal CD8 + T cells can be induced, retained as long-lasting memory, and recalled upon the challenge to provide immunity independent of the T-cell help during mouse models of Pneumocystis , Histoplasma , and Blastomyces infections ( 8 , 13 – 16 ). Antifungal activity of CD8 + T cells involves cell cytotoxicity ( 17 ) and secretion of proinflammatory cytokines; the latter often mimics CD4 + T-cell antifungal cytokine functions.…”

Extracellular and intracellular destruction of Pseudomonas aeruginosa by Dictyostelium discoideum phagocytes mobilize different antibacterial mechanisms

“…In addition to being delivered to maturing phagosomes, microbicidal molecules can also be released in the extracellular medium, a process referred to as degranulation (Faurschou & Borregaard, 2003; Mok et al., 2021; Othman et al., 2021). This allows phagocytic cells to kill uningested microorganisms in their close vicinity.…”