Immunology Overview

Immune Response and Antibody Reaction

• Streptococcal bacterial cell wall antigen can cross-react with self-antigens, leading to blood group incompatibility.
• Recipient's plasma antibodies may attack donor red blood cells (RBCs), resulting in hemolytic reactions.
• Type IV hypersensitivity is characterized by delayed immune responses, often involving T-cells rather than antibodies.

Autoimmunity and Hypersensitivity Mechanisms

• Immune system may mistakenly identify substances (e.g., drugs, foods) as threats, triggering autoimmunity.
• Antibodies (IgG or IgM) bind to target cell membranes via their Fab region, initiating an immune attack.
• Complement activation leads to the formation of a membrane attack complex, damaging target cell membranes.
• Opsonization occurs when complement proteins attract phagocytes to facilitate the destruction of target cells.

Therapeutics and Treatment Options

• Cromolyn sodium is used to mitigate allergic reactions and asthma.
• Bronchodilators are medications that relax and open airways.
• Monoclonal anti-IgE antibody, such as omalizumab, helps reduce allergic responses by targeting IgE.

Clinical Examples of Hypersensitivity

• Rheumatic fever exemplifies type II hypersensitivity, where antibodies form against Streptococcus pyogenes following untreated infections.
• Autoimmune conditions arise from the immune system's faulty recognition of self versus non-self, leading to tissue damage and disease.

Role of Dentists in Autoimmunity

• Dentists are crucial in identifying emerging autoimmune pathologies, often through oral examinations and patient history.