Functions and Types of Immune System

Immunity Types and Mechanisms

• Innate immunity is present in all normal individuals and forms the first line of defense against pathogens.
• Innate resistance components include physical barriers (skin, mucous membranes), chemical barriers (antimicrobial substances), and cellular components (phagocytes, natural killer cells).
• The immune system's ability to remember past infections is associated with adaptive immunity.
• Innate immunity discriminates among different pathogens but does not provide specific recognition.
• Acquired immunity arises from clinical or subclinical infections, developing immunological memory.
• Innate immunity is regulated by genetic and physiological factors including age, hormonal levels, and nutritional status.

Immune Cells and Functions

• Phagocytic cells involved in innate resistance include neutrophils, macrophages, and dendritic cells.
• Immunization involving exposure to microbial products like toxins is referred to as toxoid immunization.
• Innate immunity remains consistent and does not alter in intensity upon reexposure to pathogens.
• Characteristics not associated with innate immunity include specific pathogen recognition and memory.
• Components not part of innate resistance include antibodies, which are part of adaptive immunity.

Antibodies and Their Roles

• Live or killed infectious agents or their antigens are used for vaccines in adaptive immunity.
• Physiological conditions such as nutrition, age, and hormonal balance regulate innate immunity.
• Major immune response activities include pathogen recognition and activation of immune cells.
• The function of phagocytic cells is to ingest and destroy pathogens.
• Competitive inhibition in innate resistance is provided by normal microbiota.

Antibody Classes and Properties

• IgG is the most abundant antibody class in serum, facilitating immune responses.
• Molecular weight of IgM is approximately 900 kDa.
• IgG is the predominant antibody in the secondary immune response.
• IgA is the major immunoglobulin in secretions such as tear fluid, saliva, and breast milk.
• IgD primarily serves as a B-Cell receptor, playing a role in B-Cell activation.
• IgM is the first antibody produced in the primary immune response and is synthesized by neonates.
• IgG is unique as it opsonizes pathogens, activates complement, and crosses the placenta for fetal immunity.
• IgE binds to mast cells and basophils, mediating immediate hypersensitivity reactions and providing defense against helminths.

Anti-Fungal Agents and Mechanisms

• Polyenes, such as Amphotericin B, bind to ergosterol in fungal cell membranes, disrupting membrane integrity.
• Azoles inhibit the enzyme lanosterol 14α-demethylase, causing depletion of ergosterol in fungal membranes.
• Glucan synthesis inhibitors, like Caspofungin and Micafungin, act by inhibiting 1,3-D-glucan synthase, affecting cell wall integrity.
• Allylamines, such as Terbinafine, inhibit squalene epoxidase, leading to ergosterol depletion.
• Griseofulvin disrupts fungal mitotic spindle formation, preventing cell division.

Test your knowledge of the functions and types of the immune system. This quiz covers topics such as the maintenance of host cells, tissues, and organs, prevention of infections by microorganisms and tumors, and the innate immunity or resistance.