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Pathology- Adaptive immunity
Immunity mediated by antibodies
• Facilitated by proteins known as antibodies or immunoglobulins. The binding of an antigen to the Fab antigen-binding region reveals the binding sites on the Fc section, which facilitates the functions of the antibody. • Antibodies function through four primary mechanisms: • Inhibit the biological function of an essential microbial molecule, such as a binding protein or toxin. • Identify microorganisms for phagocytosis. • Initiate complement. • Stimulate cytotoxic immune cells. Antibody formation commences upon the binding of an antigen to its specific B-cell receptor on the surface of naïve B-lymphocytes, facilitated by an extra signal from CD4+ helper T-lymphocytes.
Cellular immunity • Primarily facilitated by T-lymphocytes (Fig. 1.3). CD4+ helper T-cells are activated by foreign peptides displayed by class II MHC molecules on specialized antigen-presenting cells, including dendritic cells and macrophages. Activated CD4+ helper T-cells undergo proliferation and produce cytokines that facilitate various immunological responses. Numerous subtypes of helper T-cells are identified based on the cytokines they secrete upon activation, including Th1, Th2, Th3, and Th17. CD8+ cytotoxic T-cells are activated by foreign peptides presented by class I MHC, which is expressed by all nucleated cells. Activated CD8+ cytotoxic T-cells eliminate the presenting host cell by either inducing apoptosis via the Fas ligand or by introducing a membrane pore known as perforin, through which the T-cell delivers proteolytic enzymes.
Immunity mediated by antibodies
• Facilitated by proteins known as antibodies or immunoglobulins. The binding of an antigen to the Fab antigen-binding region reveals the binding sites on the Fc section, which facilitates the functions of the antibody. • Antibodies function through four primary mechanisms: • Inhibit the biological function of an essential microbial molecule, such as a binding protein or toxin. • Identify microorganisms for phagocytosis. • Initiate complement. • Stimulate cytotoxic immune cells. Antibody formation commences upon the binding of an antigen to its specific B-cell receptor on the surface of naïve B-lymphocytes, facilitated by an extra signal from CD4+ helper T-lymphocytes.
Cellular immunity • Primarily facilitated by T-lymphocytes (Fig. 1.3). CD4+ helper T-cells are activated by foreign peptides displayed by class II MHC molecules on specialized antigen-presenting cells, including dendritic cells and macrophages. Activated CD4+ helper T-cells undergo proliferation and produce cytokines that facilitate various immunological responses. Numerous subtypes of helper T-cells are identified based on the cytokines they secrete upon activation, including Th1, Th2, Th3, and Th17. CD8+ cytotoxic T-cells are activated by foreign peptides presented by class I MHC, which is expressed by all nucleated cells. Activated CD8+ cytotoxic T-cells eliminate the presenting host cell by either inducing apoptosis via the Fas ligand or by introducing a membrane pore known as perforin, through which the T-cell delivers proteolytic enzymes.
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