Mechanism of fungal disease

The article was written by MSc Ma Van Tham - Internal Medicine Doctor, Department of Pediatrics - Neonatology - Vinmec Phu Quoc International General Hospital.

Fungal infections are one of the most common diseases in the world. Fungi exist everywhere, in soil, water, air, on plants and animals, and on the human body. When meeting favorable conditions such as hot and humid weather, the body's resistance decreases... fungi will grow and cause disease. Fungal diseases can affect both adults and children.

Fungi (Fungi or Mycetes) are organisms whose bodies are made up of one or more cells. In the structure of fungal cells with eukaryotes, this feature is different from bacteria (Bacteria or Schizomycetes). However, fungi do not have chlorophyll, so fungi are not autotrophs because they cannot synthesize carbohydrates and proteins from simple substances.
Fungi are heterotrophic organisms, fungi live in a saprophytic way on dead animals or plants or live as parasites on other living parts. Some fungi can live in both ways. The way of life of animals is by chewing, that of plants is autotroph. Whereas fungi get the necessary nutrients from the external environment by absorption.

Most fungi are saprophytic, survive and grow on plants or in soil, rarely adapting in the human body. Therefore, healthy people rarely get fungal diseases. When entering the body, the fungus causes a challenge to the host's immune system.
When a fungal spore is infected in the body, it is dormant, but it will then metabolize in the host body, germinate and grow, producing filaments to penetrate tissues. Mycelium, spores, attachment spores or yeast cells each have a different antigenic profile.
Fungi are a fast-growing microorganism and are often large in size, making it difficult for host cells to phagocytize, so the humoral immune response plays an important role. Each pathogenic fungus or each strain of the same genus will lead to a different immune mechanism.
The body's resistance plays an important role in resisting the invasion and pathogenicity of fungi. There are two defense mechanisms as follows:
Non-specific immunity: The integrity of the skin, mucous membranes, commensal microorganisms, phagocytic cells... In addition, immune globulins are involved. translation and complement. These mechanisms play an important role in the body's defense against opportunistic fungal diseases, which are less virulent. Specific immunity: Both cellular and humoral responses are involved, in which the cell-mediated immune response plays an important role. Sensitive T lymphocytes produce macrophage-activating lymphokines. Activated macrophages play an important role in the body's antifungal resistance. The pathogenicity of fungi depends on the ability to adapt to the living environment and to resist the body's defense mechanisms.